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Preface vii1.4 Characteristics of smart materials and systems 8 2.1 Traditional material classification systems 22 2.3 Classification systems for advanced and smart 4.2 Type 1 smart mate

NEW TECHNOLOGIES

Smart Materials and New Technologies For the architecture and

design professions

D Michelle Addington

Daniel L Schodek

Harvard University

Linacre House, Jordan Hill, Oxford OX2 8DP

30 Corporate Drive, Burlington, MA 01803

First published 2005

Copyright # 2005 All rights reserved

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Preface vii

1.4 Characteristics of smart materials and systems 8

2.1 Traditional material classification systems 22

2.3 Classification systems for advanced and smart

4.2 Type 1 smart materials – property-changing 834.3 Type 2 smart materials – energy-exchanging 95

5.1 Sensors, detectors, transducers and actuators:

6.2 Product technologies and forms 142

8.2 From the architect’s view to the technologist’s

Ten years ago, when we first began treading in the murkywaters of ‘‘smart’’ materials and micro-systems, we had littleinformation to guide us Although there had already beenrapid expansion in these technologies in the science andengineering fields, particularly in regard to sensor develop-ment, their entry into the design arena was, at best,idiosyncratic We found many novelty items and toys –mugs that changed color when hot coffee was poured inside,and rubber dinosaurs whose heads bobbed when connected

to a battery – and we noted that many designers werebeginning to incorporate the language of smart materials,albeit not the technologies themselves There were proposalsfor buildings to be entirely sheathed with ‘‘smart’’ gel, or for

‘‘smart’’ rooms that would deform individually for eachoccupant according to their specific physiological and psy-chological needs Precisely how this would happen remainedmysterious, and it was often presumed that the magicalabilities attributed to the smart designs were simply techni-calities that someone else – an engineer perhaps – wouldfigure out

These proposals troubled us from two aspects The first wasclearly that designers were considering these very new andsophisticated materials and technologies to fit right into theirnormative practice, making design simpler as the manifesta-tion of intentions could shift from the responsibility of thedesigner to the material itself One would no longer have tocarefully and tediously design wall articulation to create aparticular visual effect, as the material would be capable ofcreating any effect, one only had to name it In addition to thisabdication of responsibility to an as-yet undefined tech-nology, we were also concerned with the lack of interest inthe actual behavior of the technology By framing thesetechnologies from within the design practice, architects anddesigners were missing the opportunity to exploit unprece-dented properties and behaviors that should have beenleading to radically different approaches for design ratherthan only to the manifestation of designs constrained by thehegemony of existing practice

When we looked at the other end of the spectrum toexamine what scientists and engineers were doing, however,

we encountered equally problematic responses Much of the

early development had been geared toward miniaturizationand/or simplification of existing technologies – using instan-taneous labs on a chip to reduce the time of the unwieldychromatography process; replacing complex mechanicalvalves with seamless shape memory actuators As manufactur-ing processes were adapted to these specialized materials, andadvances in imaging allowed fabrication at the nano scalelevel, the development shifted from problem solving to

‘‘technology push.’’ Countless new materials and gies emerged, many looking for a home, and a potentialapplication

technolo-We were confronted with trying to fit round pegs – highlyspecific technologies – into square holes – incredibly vaguearchitectural aspirations Neither end seemed appropriate Wedid not have the kind of problems that a new technologycould easily step in to solve, nor did we have any idea aboutjust what kind of potential could be wrung from the behaviors

of these technologies We needed to bridge the very large gapbetween the owners of the relevant knowledge and theinventors of the potential applications

This transfer of knowledge has not been easy Scientific andengineering information typically enters the design realmalready ‘‘dumbed down.’’ Architects and designers don’tneed to know how something works, they just need to knowthe pragmatics – how big is it, what does it look like? Thisapproach, unfortunately, keeps the design professions atarm’s length, preventing not only the full exploitation ofthese technologies, but also denying a coherent vision of thefuture to help direct development in the science andengineering disciplines Over the last ten years, we havestruggled in our own research, and in our classes, to find thefluid medium between knowledge and application, so thatboth are served This book represents the culmination of thatdecade of investigation and experimentation

Our primary intention for the book’s content was thedevelopment of a coherent structure and language tofacilitate knowledge transfer at its highest level There arecertain phenomena and physical properties that must be fullyunderstood in order to design a behavior Fundamental forarchitects and designers is the understanding that we cannotframe these technologies within our own practice, we mustinstead inflect their deployment based on their inherentcharacteristics For example, as evidenced by the continuingdesire of architects to produce smart facades, we have atendency to ask these technologies to act at our normativescale – the scale of a building Most of these technologies,however, perform at the molecular and micro-scales How

differently might we think and design if we engaged thesescale differences rather than ignoring them?

Clearly, the knowledge about these materials and ogies within the science and engineering realms is so vast thatany given engineer will have a different knowledge set thananother, even in the same area of specialty What knowledge,then, should we bring across the divide to the designers? Weidentified some fundamental laws of physics and principles ofmaterials science that we felt could serve as the buildingblocks to allow the derivation of behaviors most relevant tothe design professions Several different materials, compo-nents and assemblies were then chosen and described toillustrate how these building blocks could be applied to helpunderstand and ultimately exploit each example’s character-istics We fully expect that the specific materials andtechnologies referred to in this book will soon becomeobsolete, but we strongly believe that the theoretical structuredeveloped herein will transcend the specifics and be applic-able to each new material that we may confront in the future

technol-Michelle AddingtonCambridge, Massachusetts

We are grateful to the many students over the last decadewho have willingly experimented with unfamiliar materialsand technologies in our courses as we explored the untappedpossibilities inherent in thinking about architecture as anetwork of transient environments A number of thesestudents have directly supported the development of thisbook; in particular, our teaching assistants and fellows: John

An, Nico Kienzl, Adriana Lira, Linda Kleinschmidt, and AndrewSimpson Nico, as our first doctoral student in the area, wasinstrumental in helping us transition to more direct hands-onworkshops for the students, and John, our most recentdoctoral student in the area, spearheaded a spin-off coursethat uses simulation techniques We would also like to thankthe two chair-persons of the architecture department –Toshiko Mori and Jorge Silvetti – who supported the devel-opment of coursework in this area that helped lead to thisbook And always, we are fortunate to have excellent facultycolleagues that we invariably rely upon for support, includingMarco Steinberg, Martin Bechthold, and Kimo Griggs

Michelle Addington and Daniel Schodek

Smart planes – intelligent houses – shape memory textiles –micromachines – self-assembling structures – color-changingpaint – nanosystems The vocabulary of the material world haschanged dramatically since 1992, when the first ‘smartmaterial’ emerged commercially in, of all things, snow skis.Defined as ‘highly engineered materials that respond intelli-gently to their environment’, smart materials have becomethe ‘go-to’ answer for the 21st century’s technological needs.NASA is counting on smart materials to spearhead the firstmajor change in aeronautic technology since the develop-ment of hypersonic flight, and the US Defense Departmentenvisions smart materials as the linchpin technology behindthe ‘soldier of the future’, who will be equipped witheverything from smart tourniquets to chameleon-like cloth-ing At the other end of the application spectrum, toys asbasic as ‘Play-Doh’ and equipment as ubiquitous as laserprinters and automobile airbag controls have already incor-porated numerous examples of this technology during thepast decade It is the stuff of our future even as it has alreadypercolated into many aspects of our daily lives.

In the sweeping ‘glamorization’ of smart materials, weoften forget the legacy from which these materials sproutedseemingly so recently and suddenly Texts from as early as

300 BC were the first to document the ‘science’ of alchemy.1Metallurgy was by then a well-developed technology prac-ticed by the Greeks and Egyptians, but many philosopherswere concerned that this empirical practice was not governed

by a satisfactory scientific theory Alchemy emerged as thattheory, even though today we routinely think of alchemy ashaving been practiced by late medieval mystics and charla-tans Throughout most of its lifetime, alchemy was associatedwith the transmutation of metals, but was also substantiallyconcerned with the ability to change the appearance, inparticular the color, of given substances While we often hearabout the quest for gold, there was an equal amount ofattention devoted to trying to change the colors of variousmetals into purple, the color of royalty Nineteenth-centurymagic was similarly founded on the desire for something to beother than it is, and one of the most remarkable predecessors

to today’s color-changing materials was represented by aningenious assembly known as a ‘blow book’ The magician

s Figure 1-1 NASA’s vision of a smart plane

that will use smart materials to ‘morph’ in

response to changing environmental

con-ditions (NASA LARC)

would flip through the pages of the book, demonstrating tothe audience that all the pages were blank He would thenblow on the pages with his warm breath, and reflip throughthe book, thrilling the audience with the sudden appearance

of images on every page That the book was composed ofpages alternating between image and blank with carefullyplaced indentions to control which page flipped in relation tothe others makes it no less a conceptual twin to the modern

‘thermochromic’ material

What, then, distinguishes ‘smart materials’? This book setsout to answer that question in the next eight chapters and,furthermore, to lay the groundwork for the assimilation andexploitation of this technological advancement within thedesign professions Unlike science-driven professions in whichtechnologies are constantly in flux, many of the designprofessions, and particularly architecture, have seen relativelylittle technological and material change since the 19thcentury Automobiles are substantially unchanged from theirforebear a century ago, and we still use the building framingsystems developed during the Industrial Revolution In ourforthcoming exploration of smart materials and new technol-ogies we must be ever-mindful of the unique challengespresented by our field, and cognizant of the fundamentalroots of the barriers to implementation Architecture height-ens the issues brought about by the adoption of newtechnologies, for in contrast to many other fields in whichthe material choice ‘serves’ the problem at hand, materialsand architecture have been inextricably linked throughouttheir history

1.1 Materials and architectureThe relationship between architecture and materials had beenfairly straightforward until the Industrial Revolution Materialswere chosen either pragmatically – for their utility andavailability – or they were chosen formally – for theirappearance and ornamental qualities Locally available stoneformed foundations and walls, and high-quality marbles oftenappeared as thin veneers covering the rough construction.Decisions about building and architecture determined thematerial choice, and as such, we can consider the pre-19thcentury use of materials in design to have been subordinate toissues in function and form Furthermore, materials were notstandardized, so builders and architects were forced to rely on

an extrinsic understanding of their properties and mance In essence, knowledge of materials was gainedthrough experience and observation Master builders were

perfor-s Figure 1-2 Wireless body temperature

sen-sor will communicate soldier’s physical state

to a medic’s helmet (Courtesy of ORNL)

those who had acquired that knowledge and the skillsnecessary for working with available materials, often throughdisastrous trial and error.

The role of materials changed dramatically with the advent

of the Industrial Revolution Rather than depending on anintuitive and empirical understanding of material propertiesand performance, architects began to be confronted withengineered materials Indeed, the history of modern archi-tecture can almost be viewed through the lens of the history

of architectural materials Beginning in the 19th century withthe widespread introduction of steel, leading to the emer-gence of long-span and high-rise building forms, materialstransitioned from their pre-modern role of being subordinate

to architectural needs into a means to expand functionalperformance and open up new formal responses Theindustrialization of glass-making coupled with developments

in environmental systems enabled the ‘international style’ inwhich a transparent architecture could be sited in any climateand in any context The broad proliferation of curtain wallsystems allowed the disconnection of the fac¸ade material fromthe building’s structure and infrastructure, freeing the mate-rial choice from utilitarian functions so that the fac¸ade couldbecome a purely formal element Through advancements

in CAD/CAM (Computer Aided Design/Computer AidedManufacturing) technologies, engineering materials such asaluminum and titanium can now be efficiently and easilyemployed as building skins, allowing an unprecedented range

of building fac¸ades and forms Materials have progressivelyemerged as providing the most immediately visible and thusmost appropriable manifestation of a building’s representa-tion, both interior and exterior As a result, today’s architectsoften think of materials as part of a design palette from whichmaterials can be chosen and applied as compositional andvisual surfaces

It is in this spirit that many have approached the use ofsmart materials Smart materials are often considered to be alogical extension of the trajectory in materials developmenttoward more selective and specialized performance For manycenturies one had to accept and work with the properties of astandard material such as wood or stone, designing toaccommodate the material’s limitations, whereas during the20th century one could begin to select or engineer theproperties of a high performance material to meet aspecifically defined need Smart materials allow even a furtherspecificity – their properties are changeable and thus respon-sive to transient needs For example, photochromic materialschange their color (the property of spectral transmissivity)

when exposed to light: the more intense the incident light,the darker the surface This ability to respond to multiplestates rather than being optimized for a single state hasrendered smart materials a seductive addition to the designpalette since buildings are always confronted with changingconditions As a result, we are beginning to see manyproposals speculating on how smart materials could begin

to replace more conventional building materials

Cost and availability have, on the whole, restricted spread replacement of conventional building materials withsmart materials, but the stages of implementation are tending

wide-to follow the model by which ‘new’ materials have ally been introduced into architecture: initially through highlyvisible showpieces (such as thermochromic chair backs andelectrochromic toilet stall doors) and later through highprofile ‘demonstration’ projects such as Diller and Scofidio’sBrasserie Restaurant on the ground floor of Mies van derRohe’s seminal Seagram’s Building Many architects furtherimagine building surfaces, walls and fac¸ades composedentirely of smart materials, perhaps automatically enhancingtheir design from a pedestrian box to an interactive arcade.Indeed, terms like interactivity and transformability havealready become standard parts of the architect’s vocabularyeven insofar as the necessary materials and technologies arefar beyond the economic and practical reality of most buildingprojects

tradition-Rather than waiting for the cost to come down and for thematerial production to shift from lots weighing pounds tothose weighing tons, we should step back and ask if we areignoring some of the most important characteristics of thesematerials Architects have conceptually been trying to fitsmart materials into their normative practice alongsideconventional building materials Smart materials, however,represent a radical departure from the more normativebuilding materials Whereas standard building materials arestatic in that they are intended to withstand building forces,smart materials are dynamic in that they behave in response toenergy fields This is an important distinction as our normalmeans of representation in architectural design privileges thestatic material: the plan, section and elevation drawings oforthographic projection fix in location and in view thephysical components of a building One often designs withthe intention of establishing an image or multiple sequentialimages With a smart material, however, we should befocusing on what we want it do, not on how we want it tolook The understanding of smart materials must then reachback further than simply the understanding of material

s Figure 1-3 The ‘heat’ chair that uses

thermochromic paint to provide a marker

of where and when the body rested on the

surface (Courtesy of Juergen Mayer H)

properties; one must also be cognizant of the fundamentalphysics and chemistry of the material’s interactions with itssurrounding environment The purpose of this book is thustwo-fold: the development of a basic familiarity with thecharacteristics that distinguish smart materials from the morecommonly used architectural materials, and speculation intothe potential of these characteristics when deployed inarchitectural design.

1.2 The contemporary design

context

Orthographic projection in architectural representationinherently privileges the surface When the three-dimen-sional world is sliced to fit into a two-dimensional represen-tation, the physical objects of a building appear as flatplanes Regardless of the third dimension of these planes, werecognize that the eventual occupant will rarely see anythingother than the surface planes behind which the structureand systems are hidden While the common mantra is thatarchitects design space the reality is that architects make(draw) surfaces This privileging of the surface drives the use

of materials in two profound ways First is that the material isidentified as the surface: the visual understanding ofarchitecture is determined by the visual qualities of thematerial Second is that because architecture is synonymouswith surface – and materials are that surface – we essentiallythink of materials as planar The result is that we tend toconsider materials in large two-dimensional swaths: exteriorcladding, interior sheathing Many of the materials that we

do not see, such as insulation or vapor barriers, are stillimagined and configured as sheet products Even materialsthat form the three-dimensional infrastructure of the build-ing, such as structural steel or concrete, can easily berepresented through a two-dimensional picture plane as

we tend to imagine them as continuous or monolithicentities Most current attempts to implement smart materials

in architectural design maintain the vocabulary of the dimensional surface or continuous entity and simply proposesmart materials as replacements or substitutes for moreconventional materials For example, there have been manyproposals to replace standard curtain wall glazing with anelectrochromic glass that would completely wrap the build-ing fac¸ade The reconsideration of smart material implemen-tation through another paradigm of material deploymenthas yet to fall under scrutiny

two-One major constraint that limits our current thinking aboutmaterials is the accepted belief that the spatial envelopebehaves like a boundary We conceive of a room as acontainer of ambient air and light that is bounded ordifferentiated by its surfaces; we consider the buildingenvelope to demarcate and separate the exterior environmentfrom the interior environment The presumption that thephysical boundaries are one and the same as the spatialboundaries has led to a focus on highly integrated, multi-functional systems for fac¸ades as well as for many interiorpartitions such as ceilings and floors In 1981, Mike Daviespopularized the term ‘polyvalent wall’, which described afac¸ade that could protect from the sun, wind and rain, as well

as provide insulation, ventilation and daylight.2His image of awall section sandwiching photovoltaic grids, sensor layers,radiating sheets, micropore membranes and weather skins has

s Figure 1-4 Aerogel has a density only three times that of air, but it can support significant weights and is a superb insulator Aerogels were discovered in 1931 but were not explored until the 1970s (NASA)

influenced many architects and engineers into pursuing the

‘super fac¸ade’ as evidenced by the burgeoning use of skin systems This pursuit has also led to a quest for a ‘super-material’ that can integrate together the many diversefunctions required by the newly complex fac¸ade Aerogelhas emerged as one of these new dream materials forarchitects: it insulates well yet still transmits light, it isextremely lightweight yet can maintain its shape Manynational energy agencies are counting on aerogel to be alinchpin for their future building energy conservation strate-gies, notwithstanding its prohibitive cost, micro-structuralbrittleness and the problematic of its high insulating value,which is only advantageous for part of the year and can bequite detrimental at other times

double-1.3 The phenomenological

boundary

Missing from many of these efforts is the understanding ofhow boundaries physically behave The definition of bound-ary that people typically accept is one similar to that offered

by the Oxford English Dictionary: a real or notional linemarking the limits of an area As such, the boundary is staticand defined, and its requirement for legibility (marking)prescribes that it is a tangible barrier – thus a visual artifact.For physicists, however, the boundary is not a thing, but anaction Environments are understood as energy fields, and theboundary operates as the transitional zone between differentstates of an energy field As such, it is a place of change as anenvironment’s energy field transitions from a high-energy tolow-energy state or from one form of energy to another.Boundaries are therefore, by definition, active zones ofmediation rather than of delineation We can’t see them,nor can we draw them as known objects fixed to a location.Breaking the paradigm of the hegemonic ‘material as visualartifact’ requires that we invert our thinking; rather thansimply visualizing the end result, we need to imagine thetransformative actions and interactions What was once a bluewall could be simulated by a web of tiny color-changingpoints that respond to the position of the viewer as well as tothe location of the sun Large HVAC (heating, ventilating andair conditioning) systems could be replaced with discretelylocated micro-machines that respond directly to the heatexchange of a human body In addition, by investigating thetransient behavior of the material, we challenge the privile-ging of the static planar surface The ‘boundary’ is no longer

delimited by the material surface, instead it may be gured as the zone in which change occurs The image of thebuilding boundary as the demarcation between two differentenvironments defined as single states – a homogeneousinterior and an ambient exterior – could possibly be replaced

reconfi-by the idea of multiple energy environments fluidly ing with the moving body Smart materials, with theirtransient behavior and ability to respond to energy stimuli,may eventually enable the selective creation and design of anindividual’s sensory experiences

interact-Are architects in a position or state of development toimplement and exploit this alternative paradigm, or, at thevery least, to rigorously explore it? At this point, the answer ismost probably no, but there are seeds of opportunity fromon-going physical research and glimpses of the future use ofthe technology from other design fields Advances in physicshave led to a new understanding of physical phenomena,advances in biology and neurology have led to new dis-coveries regarding the human sensory system Furthermore,smart materials have been comprehensively experimentedwith and rapidly adopted in many other fields – finding theirway into products and uses as diverse as toys and automotivecomponents Our charge is to examine the knowledge gained

in other disciplines, but develop a framework for its tion that is suited to the unique needs and possibilities ofarchitecture

applica-1.4 Characteristics of smart materials and systems

DEFINITIONS

We have been liberally using the term ‘smart materials’without precisely defining what we mean Creating a precisedefinition, however, is surprisingly difficult The term isalready in wide use, but there is no general agreementabout what it actually means A quick review of the literatureindicates that terms like ‘smart’ and ‘intelligent’ are usedalmost interchangeably by many in relation to materials andsystems, while others draw sharp distinctions about whichqualities or capabilities are implied NASA defines smartmaterials as ‘materials that ‘‘remember’’ configurations andcan conform to them when given a specific stimulus’,3 adefinition that clearly gives an indication as to how NASAintends to investigate and apply them A more sweeping

Technology: ‘smart materials and structures are those objectsthat sense environmental events, process that sensory infor-mation, and then act on the environment’.4 Even thoughthese two definitions seem to be referring to the same type ofbehavior, they are poles apart The first definition refers tomaterials as substances, and as such, we would think ofelements, alloys or even compounds, but all would beidentifiable and quantifiable by their molecular structure.The second definition refers to materials as a series of actions.Are they then composite as well as singular, or assemblies ofmany materials, or, even further removed from an identifiablemolecular structure, an assembly of many systems?

If we step back and look at the words ‘smart’ and

‘intelligent’ by themselves we may find some cues to help

us begin to conceptualize a working definition of ‘smartmaterials’ that would be relevant for designers ‘Smart’implies notions of an informed or knowledgeable response,with associated qualities of alertness and quickness Incommon usage, there is also frequently an association withshrewdness, connoting an intuitive or intrinsic response.Intelligent is the ability to acquire knowledge, demonstrategood judgment and possess quickness in understanding.Interestingly, these descriptions are fairly suggestive of thequalities of many of the smart materials that are of interest to

us Common uses of the term ‘smart materials’ do indeedsuggest materials that have intrinsic or embedded quickresponse capabilities, and, while one would not commonlythink about a material as shrewd, the implied notions ofcleverness and discernment in response are not withoutinterest The idea of discernment, for example, leads one tothinking about the inherent power of using smart materialsselectively and strategically Indeed, this idea of a strategic use

is quite new to architecture, as materials in our field are rarelythought of as performing in a direct or local role.Furthermore, selective use hints at a discrete response – asingular action but not necessarily a singular material.Underlying, then, the concept of the intelligent and designedresponse is a seamless quickness – immediate action for aspecific and transient stimulus

Does ‘smartness’, then, require special materials andadvanced technologies? Most probably no, as there is nothing

a smart material can do that a conventional system can’t Aphotochromic window that changes its transparency inrelation to the amount of incident solar radiation could bereplaced by a globe thermometer in a feedback control loopsending signals to a motor that through mechanical linkagesrepositions louvers on the surface of the glazing, thus

changing the net transparency Unwieldy, yes, but theless feasible and possible to achieve with commonly usedtechnology and materials (Indeed, many buildings currentlyuse such a system.) So perhaps the most unique aspects ofthese materials and technologies are the underlying conceptsthat can be gleaned from their behavior.

never-Whether a molecule, a material, a composite, an assembly,

or a system, ‘smart materials and technologies’ will exhibit thefollowing characteristics:

* Immediacy – they respond in real-time

* Transiency – they respond to more than one environmentalstate

* Self-actuation – intelligence is internal to rather thanexternal to the ‘material’

* Selectivity – their response is discrete and predictable

* Directness – the response is local to the ‘activating’ event

It may be this last characteristic, directness, that poses thegreatest challenge to architects Our building systems areneither discrete nor direct Something as apparently simple aschanging the temperature in a room by a few degrees will setoff a Rube Goldberg cascade of processes in the HVAC system,affecting the operation of equipment throughout the build-ing The concept of directness, however, goes beyond makingthe HVAC equipment more streamlined and local; we mustalso ask fundamental questions about the intended behavior

of the system The current focus on high-performancebuildings is directed toward improving the operation andcontrol of these systems But why do we need these particularsystems to begin with?

The majority of our building systems, whether HVAC,lighting, or structural, are designed to service the buildingand hence are often referred to as ‘building services’.Excepting laboratories and industrial uses, though, buildingsexist to serve their occupants Only the human body requiresmanagement of its thermal environment, the building doesnot, yet we heat and cool the entire volume The human eyeperceives a tiny fraction of the light provided in a building,but lighting standards require constant light levels through-out the building If we could begin to think of theseenvironments at the small scale – what the body needs –and not at the large scale – the building space – we coulddramatically reduce the energy and material investment ofthe large systems while providing better conditions for thehuman occupants When these systems were conceived over

a century ago, there was neither the technology nor the

knowledge to address human needs in any manner otherthan through large indirect systems that provided homo-geneous building conditions The advent of smart materialsnow enables the design of direct and discrete environmentsfor the body, but we have no road map for their application

in this important arena

1.5 Moving forward

Long considered as one of the roadblocks in the developmentand application of smart materials is the confusion over whichdiscipline should ‘own’ and direct the research efforts as well

as oversee applications and performance Notwithstandingthat the ‘discovery’ of smart materials is attributed to twochemists (Jacques and Pierre Curie no less!), the disciplines ofmechanical engineering and electrical engineering currentlysplit ownership Mechanical engineers deal with energystimuli, kinematic (active) behavior and material structure,whereas electrical engineers are responsible for microelec-tronics (a fundamental component of many smart systemsand assemblies), and the operational platform (packaging andcircuitry) Furthermore, electrical engineers have led theefforts toward miniaturization, and as such, much of thefabrication, which for most conventional materials would behoused in mechanical engineering, is instead under theumbrella of electrical engineering

This alliance has been quite effective in the development ofnew technologies and materials, but has been less so in regard

to determining the appropriate applications As a result, thesmart materials arena is often described as ‘technology push’

or, in other words, technologies looking for a problem.Although this is an issue that is often raised in overviewsand discussions of smart materials, it has been somewhatnullified by the rapid evolution and turnover of technologies

in general Many industries routinely adopt and discardtechnologies as new products are being developed and oldones are upgraded As soon as knowledge of a new smartmaterial or technology enters the public realm, industries ofall sizes and of all types will begin trying it out, eliminating theround pegs for the square holes This trial and error ofmatching the technology to a problem may well open upunprecedented opportunities for application that would havegone undetected if the more normative ‘problem first’developmental sequence had occurred For architecture,however, this reversal is much more problematic

In most fields, technologies undergo continuous cycles ofevolution and obsolescence as the governing science matures;

as a result, new materials and technologies can be easilyassimilated In architecture, however, technologies have verylong lifetimes, and many factors other than science determinetheir use and longevity There is no mechanism by which newadvances can be explored and tested, and the small profitmargin in relation to the large capital investment of construc-tion does not allow for in situ experimentation Furthermore,buildings last for years – 30 on average – and many last for acentury or more In spite of new construction, the yearlyturnover in the building stock is quite low Anything new must

be fully verified in some other industry before architects canpragmatically use it, and there must also be a match with aclient who is willing to take the risk of investing in anytechnology that does not have a proven track record.The adoption of smart materials poses yet anotherdilemma for the field of architecture Whereas architectschoose the materials for a building, engineers routinelyselect the technologies and design the systems Smartmaterials are essentially material systems with embeddedtechnological functions, many of which are quite sophisti-cated Who, then, should make the decisions regarding theiruse? Compounding this dilemma are the technologies at theheart of smart materials; the branches of mechanical andelectrical engineering responsible for overseeing this areahave virtually no connection to or relationship with theengineering of building systems Not only are smartmaterials a radical departure from the more normativematerials in appearance, but their embedded technologyhas no precedent in the large integrated technologicalsystems that are the standard in buildings

How can architects and designers begin to explore andexploit these developing technologies and materials, with therecognition that their operating principles are among themost sophisticated of any technologies in use? Althougharchitecture is inherently an interdisciplinary profession, itspractice puts the architect at the center, as the director of theprocess and the key decision-maker The disciplines that wemust now reach out to, not only mechanical and electricalengineering, but also the biological sciences, have littlecommon ground There are no overlapping boundaries inknowledge, such as you might find between architecture andurban design, and there is no commonality of problem, such

as you might find between architecture and ecology Ourknowledge base, our practice arena, and even our languageare split from those in the smart materials domain Ultimately,our use of these materials will put us into the heady role ofmanipulating the principles of physics

1.6 Organization of the text

The objectives of this book are thus three-fold The first is toprovide a primer on smart materials, acquainting architectsand designers with the fundamental features, properties,behaviors and uses of smart materials Of particular importance

is the development of a vocabulary and a descriptive languagethat will enable the architect to enter into the world of thematerial scientist and engineer The second objective is theframing of these new materials and technologies as behaviors

or actions and not simply as artifacts We will be describingsmart materials in relation to the stimulus fields that surroundthem Rather than categorizing materials by application orappearance, we will then categorize them in relation to theiractions and their energy stimulus Our third objective is thedevelopment of a methodological approach for working withthese materials and technologies We will successively buildsystems and scenarios as the book progresses, demonstratinghow properties, behaviors, materials and technologies can becombined to create new responses If these three objectives aremet, the designer will be able to take a more proactive stance

in determining the types of materials and systems that should

be developed and applied Furthermore, competency in thefoundations of energy and material composition behavior willeventually allow the architect or designer to think at aconceptual level ‘above’ that of the material or technology.One of the constants in the field of smart materials is that theyare continuously being updated or replaced If we understandclasses of behaviors in relation to properties and energy fields,then we will be able to apply that understanding to any newmaterial we may ‘meet’ in the future

To pull these objectives together, the overall organization

of the book follows a bipartite system; categories of behaviorwill be established and then will be overlaid with increasingcomponent and system complexity Chapter 2 serves as theentry into the subject of material properties and materialbehavior, whereas Chapter 3 first posits the frameworkthrough which we will categorize smart materials We willestablish a basic relationship between material properties,material states and energy that we can use to describe theinteraction of all materials with the environments – thermal,luminous and acoustic – that surround the human body Thisbasic relationship forms a construct that allows us to under-stand the fundamental mechanisms of ‘smartness’ Theresulting construct will form the basis not only for thecategories, but will also be useful as we discuss potentialcombinations and applications

Smartness in a material or system is determined by one oftwo mechanisms, which can be applied directly to a singularmaterial, and conceptually to a compound system (althoughindividual components may well have one of the directmechanisms) If the mechanism affects the internal energy

of the material by altering either the material’s molecularstructure or microstructure then the input results in a propertychange of the material (The term ‘property’ is important inthe context of this discussion and will be elaborated uponlater Briefly, the properties of a material may be eitherintrinsic or extrinsic Intrinsic properties are dependent on theinternal structure and composition of the material Manychemical, mechanical, electrical, magnetic and thermalproperties of a material are normally intrinsic to it Extrinsicproperties are dependent on other factors The color of amaterial, for example, is dependent on the nature of theexternal incident light as well as the micro-structure of thematerial exposed to the light.) If the mechanism changes theenergy state of the material, but does not alter the materialper se, then the input results in an exchange of energy fromone form to another A simple way of differentiating betweenthe two mechanisms is that for the property change type(hereafter defined as Type I), the material absorbs the inputenergy and undergoes a change, whereas for the energyexchange type (Type II), the material stays the same but theenergy undergoes a change We consider both of thesemechanisms to operate directly at the micro-scale, as nonewill affect anything larger than the molecule, and further-more, many of the energy-exchanges take place at the atomiclevel As such, we cannot ‘see’ this physical behavior at thescale at which it occurs

HIGH-PERFORMANCE VERSUS SMART MATERIALS

We will soon begin to use the construct just described tobegin characterizing smart materials, and specifically look atmaterials that change their properties in response to varyingexternal stimuli and those that provide energy transformationfunctions This construct is specific to smart materials It doesnot reflect, for example, many extremely exciting and usefulnew materials currently in vogue today Many of theseinteresting materials, such as composites based on carbonfibers or some of the new radiant mirror films, change neithertheir properties nor provide energy transfer functions; andhence are not smart materials Rather, they are what mightbest be described as ‘high-performance’ materials They often

s Figure 1-5 Radiant color film The color of

the transmitted or reflected light depends

upon the vantage point Observers at

dif-ferent places would see difdif-ferent colors (see

Chapter 6)

have what might be called ‘selected and designed properties’(e.g., extremely high strength or stiffness, or particularreflective properties) These particular properties have beenoptimized via the use of particular internal material structures

or compositions These optimized properties, however, arestatic Nevertheless, we will still briefly cover selected highperformance materials later in Chapter 4 because of the waythey interact with more clearly defined smart materials

TYPE 1 MATERIALS

Based on the general approach described above, smartmaterials may be easily classified in two basic ways In oneconstruct we will be referring to materials that undergochanges in one or more of their properties – chemical,mechanical, electrical, magnetic or thermal – in directresponse to a change in the external stimuli associated withthe environment surrounding the material Changes are directand reversible – there is no need for an external controlsystem to cause these changes to occur A photochromicmaterial, for example, changes its color in response to achange in the amount of ultraviolet radiation on its surface

We will be using the term ‘Type 1’ materials to distinguish thisclass of smart materials

Chapter 4 will discuss these materials in detail Briefly,some of the more common kinds of Type 1 materials includethe following:

* Thermochromic – an input of thermal energy (heat) to thematerial alters its molecular structure The new molecularstructure has a different spectral reflectivity than does theoriginal structure; as a result, the material’s ‘color’ – itsreflected radiation in the visible range of the electro-magnetic spectrum – changes

* Magnetorheological – the application of a magnetic field(or for electrorheological – an electrical field) causes a

s Figure 1-6 Design experiment: view directional film and radiant color film have been used together in this fac¸ade study (Nyriabu Nyriabu)

change in micro-structural orientation, resulting in achange in viscosity of the fluid.

* Thermotropic – an input of thermal energy (or radiation for

a phototropic, electricity for electrotropic and so on) to thematerial alters its micro-structure through a phase change

In a different phase, most materials demonstrate differentproperties, including conductivity, transmissivity, volu-metric expansion, and solubility

* Shape memory – an input of thermal energy (which canalso be produced through resistance to an electricalcurrent) alters the microstructure through a crystallinephase change This change enables multiple shapes inrelationship to the environmental stimulus

s Figure 1-7 A ‘cloth’ made by weaving fiber-optic strands that are lighted by light-emitting diodes (LEDs) (Yokiko Koide)

TYPE 2 MATERIALS

A second general class of smart materials is comprised of thosethat transform energy from one form to an output energy inanother form, and again do so directly and reversibly Thus,

an electro-restrictive material transforms electrical energy intoelastic (mechanical) energy which in turn results in a physicalshape change Changes are again direct and reversible Wewill be calling these ‘Type 2’ materials Among the materials inthis category are piezoelectrics, thermoelectrics, photo-voltaics, pyroelectrics, photoluminescents and others.Chapter 4 will also consider these types of materials atlength The following list briefly summarizes some of the morecommon energy-exchanging smart materials

* Photovoltaic – an input of radiation energy from the visiblespectrum (or the infrared spectrum for a thermo-photo-voltaic) produces an electrical current (the term voltaicrefers more to the material which must be able to providethe voltage potential to sustain the current)

* Thermoelectric – an input of electrical current creates atemperature differential on opposite sides of the material.This temperature differential produces a heat engine,essentially a heat pump, allowing thermal energy to betransferred from one junction to the other

* Piezoelectric – an input of elastic energy (strain) produces

an electrical current Most piezoelectrics are bi-directional

in that the inputs can be switched and an applied electricalcurrent will produce a deformation (strain)

* Photoluminescent – an input of radiation energy from theultraviolet spectrum (or electrical energy for an electro-luminescent, chemical reaction for a chemoluminescent) isconverted to an output of radiation energy in the visiblespectrum

* Electrostrictive – the application of a current (or a magneticfield for a magnetostrictive) alters the inter-atomic distancethrough polarization A change in this distance changes theenergy of the molecule, which in this case produces elasticenergy – strain This strain deforms or changes the shape ofthe material

With Type 2 materials, however, we should be aware thatuse of the term ‘material’ here can be slightly misleading.Many of the ‘materials’ in this class are actually made up ofseveral more basic materials that are constituted in a way toprovide a particular type of function A thermoelectric, forexample, actually consists of multiple layers of different

materials The resulting assembly is perhaps better described

as a simple device The term ‘material’, however, has stillcome to be associated with these devices – largely because ofthe way they are conceptually thought about and used.Application-oriented thinking thus drives use of the term

or actuators In their role as sensors, a smart material responds

to a change in its environment by generating a perceivableresponse Thus, a thermochromic material could be useddirectly as a device for sensing a change in the temperature of

an environment via its color response capabilities Othermaterials, such as piezoelectric crystals, could also be used asactuators by passing an electric current through the material

to create a force Many common sensors and actuators arebased on the use of smart materials

In the use of Type 2 materials as a sensor or actuator, thereare also different kinds of electronic systems that are integral

to the system to amplify, modify, transmit, or interpretgenerated signals Logic capabilities provided via micro-processors or other computer-based systems are similarlycommon There are several different types of strategiespossible here We will return to this topic in Chapter 5

COMPONENTS AND SYSTEMS

As is common in any design context, basic types of smartmaterials are normally used in conjunction with many othermaterials to produce devices, components, assemblies and/orsystems that serve more complex functions As was previouslymentioned, external walls in a building, for example, provide

a range of pragmatic functions (thermal barrier, weatherenclosure, ventilation, etc.) as well as establishing the visualexperience of a building Single materials cannot respond tothese many demands alone Thus, we might have a wholeseries of different types of ‘smart walls’ depending on exactlyhow the wall is constituted, what primary functions it isintended to serve and the degree to which there are externallogic controls

In addition to constructions that we normally think of ascomponents, we also have whole systems in buildings thatcan be designed to possess some level of smartness The

systems of concern here include normal environmentalsystems (heating, ventilation and air conditioning; lighting;acoustical) and structural systems Historically, one of the firstuses of the term ‘smart’ was in connection with improvedsensor-based monitoring and control systems for controllingthe thermal environment in a building (the ‘Smart House’ ofthe 1990s) Whether or not this approach is commensuratewith the term ‘smart’ as it is used today is an interestingquestion, and one that we will return to in Chapter 7 In thatchapter we will consider different kinds of smart systems inuse today.

SMART VS INTELLIGENT ENVIRONMENTS

Fundamentally, the product of architecture and design is acomplete work – whether a building or a lamp Inherent toeach, however, is a stunning complexity in all of its aspects.Here the question is naturally raised of the notion of smartand/or intelligent environments The term ‘intelligent’ itself is

as problematic as the term ‘smart’, yet it surely suggestssomething of a higher level than does ‘smart’ We do expectmore out of ‘intelligent systems’ than we do from ‘smartmaterials’ Everyday connotations of the term ‘intelligent’with suggested notions of abilities to understand or compre-hend, or having the power of reflection or reason, could beuseful, and will help us as we examine the current conceptions

of these environments and develop new ones of our own.One of the more fascinating aspects of today’s society ishow ‘techno-speak’ terms come into existence and assumecurrency without universal agreement about what is actuallymeant There has been a lot of recent interest in ‘intelligentrooms’ and ‘intelligent buildings’ without a clear consensusabout what is actually meant by these terms The parallelquestion raised of whether common rooms or buildings are

‘dumb’ is equally interesting, particularly since architects andbuilders have done rather well at responding to societal andcultural needs for millennia More specific fundamental needshave not been ignored, nor have the wonderful vicissitudes ofhuman desire So, presumably, something else and morespecific is meant by the terms ‘intelligent rooms’ or ‘intelli-gent buildings’, but what? Here we also engage in anothermeaning conundrum The phrase ‘smart environments’ is inwidespread use and has already been employed in this book.What, if anything, is the difference between an environment

or building space that is ‘intelligent’ and one that is ‘smart?’The engineering and computer science worlds often do notdistinguish between the two, presuming that both represent

s Figure 1-8 Current smart room and

intel-ligent room paradigms, with a glimpse into

the future (see Chapter 8)

the crowning culmination of technological development –that of the fully contained and controlled environment InChapters 8 and 9, we begin to propose an alternative in whichsystems become smaller and more discrete, freeing our bodiesand our environments from an overarching web of control It

is perhaps in this arena that architects can have the mostimpact on the trajectory of these advanced materials andtechnologies

Notes and references

1 All discussion on alchemy in this chapter is from David C.Lindberg (ed.), Science in the Middle Ages (Chicago: TheUniversity of Chicago Press, 1978) See in particular chapter

11 on the ‘Science of Matter’

2 Davies, M (1981) ‘A wall for all seasons’, RIBA Journal, 88 (2),

pp 55–57 The term ‘polyvalent wall’, first introduced in thisarticle, has become synonymous with the ‘advanced fac¸ade’and most proposals for smart materials in buildings are based

on the manifestation of this 1981 ideal

3 http://virtualskies.arc.nasa.gov/research/youDecide/

smartMaterials.html

4 Kroschwitz, J (ed.) (1992) Encyclopedia of ChemicalTechnology New York: John Wiley & Sons

Chapter 1 provided a brief insight into how smart materialsand systems might affect our design thinking We identifiedfive ‘conceptual’ characteristics – immediacy, transiency, self-actuation, selectivity and directness – that differentiated thesematerials from more traditional materials, but we need furtherinformation regarding the ‘physical’ characteristics of thesematerials and technologies For example, how do we measuretransiency? Or what defines discretion in an assembly? Asdesigners, we understand conceptual characteristics as inten-tions, whereas engineers understand physical characteristics

as tools in implementation This chapter will begin to lay outthe tangible definitions that are necessary for bridging thisgap in knowledge and in application In order to achieve this

we must directly address the question of how best to classifythese materials Classification systems and related taxonomiesare useful not only for simple categorization and descriptionpurposes, but they can invariably suggest more far-reachingfundamental constructs of a field This precept is particularlyimportant in our current context in which the smart materialsfield is just emerging Examining the structure of differentclassifications for materials will help us to place smartmaterials within a broader context After reviewing severalexisting and common approaches for classification, we willdevelop our own structure that marries the intentions of thearchitect with the tools of the engineer

The latter half of this chapter will provide the necessaryoverview of materials science, beginning with atomic struc-ture and concluding with material properties Fundamental tothe development of a new construct for the exploitation ofthese materials in the design professions is an understanding

of the origin and determinants of their behaviors Just as theresponses of these materials are discrete and direct, then ourinteraction with them must ultimately function at the samescale, whether atomic, molecular, or micro-structural.Designers are used to manipulating materials at the objectscale, and while a large-scale interaction will invariably impactsmaller-scale behavior, we can operate more efficiently,predictably and quickly if we act directly on the rootmechanism of the behavior

2.1 Traditional material classification systemsThere are a number of existing classification and descriptivesystems used in connection with materials One broadapproach stems from a fairly basic materials science approach

to the subject matter, wherein the primary point of viewrevolves around the internal structure of the material Anotherapproach commonly used in the engineering profession isessentially descriptive but focuses on the performance char-acteristics of materials In the design fields, a host of differentloose categorizations are used, many of which are particular(and perhaps idiosyncratic) to individual fields For example,interior designers maintain classification types that aredistinctly different from those used in landscape architecture.There are also various kinds of classifications that literallyprovide the legal basis for the specification of materials indesign works In general, we will see that each material systemadopts a particular point of view that is useful to a particularconstruct of the field and/or for a particular application Theconstruct may have no overlap or applicability for anothergroup Hence, it is important to understand these points ofview

MATERIAL SCIENCE CLASSIFICATIONS

The material science approach to classification goes directly tothe core understanding of the basic internal structure ofmaterials As a result, we might consider this system to becompositionally driven The most fundamental level of differ-entiation begins with the bonding forces between individualatoms It is this bonding force, whether ionic, covalent,metallic or Van der Waals, that will ultimately determinemany of the intrinsic properties and major behavioraldifferences between materials The next level of descriptionhinges on the way these bonding forces produce differenttypes of aggregation patterns between atoms to form variousmolecular and crystalline solid structures These larger aggre-gation patterns can further be differentiated by how theirmolecular structures branch or link or, in crystalline solids, bydifferent types of unit cell and related spatial lattice structuressuch as face-centered or body-centered Diamond, forexample, is a covalently bonded material with a cubic crystalstructure At the highest level are the broadly descriptivecategories such as ceramics, metals or polymers, which arefamiliar to us even insofar as the boundaries between these

classes are not nearly as distinct as at the lower levels of theclassification system – silicones exist between ceramics andplastics, and many semiconductors could be either a metal orceramic.

This way of classifying materials is extremely useful formany reasons In particular, the understandings reflected inthe classifications provide a way of describing the specificqualities or properties (e.g., hardness, electrical conductivity)that characterize different materials Knowledge of properties

at the atomic and molecular level can transform ourimpression of smart materials from ‘gee-whiz’ materials into

an understanding of them through scientifically describedattributes and behaviors Consequently, it also provides abasis for developing a method for designing materials thatpossess different qualities or properties

ENGINEERING CLASSIFICATIONS

Applied classification approaches are shown in Figures 2–1and 2–2 These types are primarily used in the mechanicalengineering profession to distinguish between the funda-mental problem-solving characteristics of the nearly 300 000materials readily available to the engineer (steel alone has over

2000 varieties) Rather than the hierarchical organization ofthe material scientist, the engineering classification is one ofmapping, enabling the engineer to mix and match propertiesand attributes to best solve the problem or need at hand.Materials in the engineering realm are chosen based on whatthey can do, how they behave and what they can withstand.The physical criteria for the use are first determined, and amaterial is selected or engineered to provide the best fit or, atthe very least, the most acceptable compromise for thespecific criteria If the material science classification describeshow a material is composed, then the engineering classifica-tion explains what it does Furthermore, since the focus isalways a practical one, i.e the material will be used in aproduct or process, many of the categories are quitepragmatic For example, an important category is theenvironment of the application: can the material function in

a corrosive atmosphere, can it withstand being submerged insea water? Still other engineering classifications might includecost, availability, or recyclability as categories of equalimportance to the more basic descriptive ones such as stateand composition Even though the final objective in allengineering applications is the optimization of a materialproperty for a particular situation, regardless of the materialtype, the additional criteria will quickly narrow down the

s Figure 2-1 Basic organization of material

catgeories in the engineering profession with

a few examples in each category Engineers

must weigh many of these characteristics in

choosing a material (Adapted from Myer

P Kutz (ed.), The Mechanical Engineer’s

Handbook New York: John Wiley, 1998)

s Figure 2-2 This classification system for materials is typical of those used in applied engineering It readily mixes the form of material structures (e.g., laminates, amorphous) with properties (ferrous, nonferrous), but can be very useful for many applications It is difficult to use this kind of classification, however, to describe smart materials with property-changing or energy-exchanging characteristics (Diagram modeled after Fig 31-9 in Myer P Kutz (ed.), The Mechanical Engineer’s Handbook New York: John Wiley, 1998)

seemingly endless choices Many industries have developedtheir own classification systems to help narrow down thechoice of materials to those that are appropriate for their ownuses For example, the American Iron and Steel Institute,which deals only with ferrous materials, adopted a straightfor-ward numbering system that encompasses alloy composition,carbon content and processing method The AmericanWelding Association is even more specific, categorizingelectrode materials by tensile strength, welding techniqueand position Regardless of the source of the classificationsystem, each one clearly highlights properties that underpinthe useful behavior of the material.

The behavior focus of the engineering classification is not

as likely to lead toward the direct development of newmaterials as would be supported by the more compositionallyfocused system of the materials scientist Nevertheless, byworking toward the optimization of a property, rather than of

a material, this focus on behavior is friendlier toward newmaterials Desired behaviors, as defined by material proper-ties, have no preference for specific materials or technologies,and, as a result, will be more suitable for and more open toexperimentation and novel solutions

TRADITIONAL ARCHITECTURAL CLASSIFICATIONS

There are several material classification approaches that haveevolved over the years for describing the materials used inarchitectural settings Many have a mix of classificationperspectives, and are rarely based on pure performancerequirements, as would be characteristic in engineering fields.Architectural building codes and standards, for example,often supersede performance criteria in an attempt to simplifythe selection process and remove liability for performancefailures For many uses, codes and standards often explicitly orimplicitly identify acceptable materials, leaving the architectonly to select between brands As a result, architecturalclassifications tend to be more nominative – simply listingmaterials and uses in accordance with standard buildingrequirements

Within architectural practice, these various requirementsare codified in different ways In the United States, theConstruction Specifications Institute has maintained a stan-dardized classification system for over 50 years This system,known as the CSI index, organizes materials in two ways Thefirst places the materials typically used in a building into broadclasses In this section, we will find generic material groupingssuch as paint, laminate and concrete The second organizes

by component or system These categories are equally genericand, furthermore, are not even material-specific For example,windows fall into this category, even though they may bemanufactured with wood, vinyl, aluminum or steel Theemphasis in both major groupings is toward application andcommon use; the fundamental behaviors and properties areincidental In the broad material classes, the properties,performance and behavior are largely presumed to besatisfactory as long as the chosen material fits within thenormative uses defined by practice For example, thecharacteristics of wood are discussed in relationship to theirrelevance for the intended application: the grade of woodsuitable for load-bearing roof structures, or the type of woodsuitable for finish flooring The system or component classesfocus on application as well Doors are organized according totheir suitability for security, fire protection, egress, as well as

by their use for commercial or residential buildings

The CSI index also addresses the technologies typicallyused in buildings, grouping them into operational systems,such as heating, ventilating and air conditioning (HVAC),lighting and plumbing, and into constructional systems, such

as structural, drainage and vertical circulation This too differssubstantially from the method for categorizing technologies

in the engineering fields in which technologies are routinelyorganized by their process – e.g smelting or CAD/CAM – or

by their mechanism of operation – compression or pumping.Fewer specifics are made available to architects on thesesystems, as it is presumed that an engineer will be responsiblefor selecting building technologies

Essentially, if the materials science classification explains

‘why one material is differentiated from another’, and theengineering classification determines ‘how a material per-forms’, then the architectural classifications operates at theother end of the sequence by listing ‘what a material is andwhere it is used’ This system is intended to remove thedecision-making responsibility from the architect, and as such,

it is less about informed choice and optimization and moreabout specification and standardization The result is informa-tion, not knowledge

This general approach is often the framework into whichapplications of new materials in architecture are forced to fit,and it has clearly proved problematic in this regard.Classification systems such as that of the CSI are not intended

to spur innovation in the materials field Rather, they arepractical templates for communication between architects,contractors, fabricators and suppliers After the preliminarydesign of a building is completed and approved, architects

s Figure 2-3 The Construction Specifications

Institute (CSI) Master Format is a standard

outline for construction specifications in the

United States To illustrate the depth of this

format, Division 8 is presented in its

expanded form

prepare construction documents that serve as the tions’ for the construction of the building A textual documentdefines each building element on the design drawings andspecifies the material or component This document, ratherthan providing guidelines, instead serves as a binding contractthat construction professionals and contractors must follow.Trade associations and manufacturers of building productsroutinely write their material and product specifications in thisformat to streamline the specification process for architects,and many architectural firms maintain an internal set ofconstruction specifications that are used as the baseline for all

‘instruc-of their projects While communication and contractualapplications are important, particularly in a field that hasdirect responsibility for the public’s safety and welfare, theperipheral consequences of a specification-driven systemgenerally result in the exclusion of new and unusual materialsand technologies

2.2 Alternative classification

systems

Nevertheless, there have been many attempts to introducenew materials to designers through alternative classificationsystems Many are quite qualitative and readily mixapproaches to description, but almost all invert the criteria-driven process that characterize the materials science andengineering systems In many design fields the material ischosen long before performance criteria are defined and assuch the process tends to be artifact-driven The rationale forthis comes from many fronts, not all of which are based onphysical requirements reflected in the mechanical engineeringclassification approach or the internal structuring of thematerial science perspective

A good example of this general approach is reflected in thebook Technotextiles, which converges on a specific subset ofmaterials intended for use in the fashion design profession.Terms such as Fibres and Fabrics, Electronic Textiles,Engineered Textiles and Textile Finishes are used broadly tocharacterize the materials described in the book.1 Thesecategories are used to describe and illustrate many of thetextiles used in the fashion design industry Several descrip-tions are by the finishing process (e.g., Heat-transfer, Ink-Jet),

Composites), several by broad designations of material type(Glass, Metal), others by use (Coatings) and still others by