Rapid determination hexavalent chromium in tap water by using a microfluidic dilution chip

THAI NGUYEN UNIVERSITY UNIVERSITY OF AGRICULTURE AND FORESTRY TA THI VIET NGA RAPID DETERMINATION HEXAVALENT CHROMIUM IN TAP WATER BY USING A MICROFLUIDIC DILUTION CHIP BACHELOR THES

THAI NGUYEN UNIVERSITY

UNIVERSITY OF AGRICULTURE AND FORESTRY

TA THI VIET NGA

RAPID DETERMINATION HEXAVALENT CHROMIUM

IN TAP WATER BY USING A MICROFLUIDIC DILUTION CHIP

BACHELOR THESIS

Study Mode : Full-time

Major : Environmental Science and Management

Thai Nguyen, September, 2015

THAI NGUYEN UNIVERSITY

UNIVERSITY OF AGRICULTURE AND FORESTRY

TA THI VIET NGA

Topic title:

RAPID DETERMINATION HEXAVALENT CHROMIUM

IN TAP WATER BY USING A MICROFLUIDIC DILUTION CHIP

BACHELOR THESIS

Study Mode : Full-time

Major : Environmental Science and Management

Superviors : Prof Yuh-Chang Sun

Ph.D Nguyen Huu Tho

Thai Nguyen, September, 2015

DOCUMENTATION PAGE WITH ABSTRACT

Thai Nguyen University of Agriculture and Forestry

water by using a Microfluidic dilution chip

The study described a methodology of using a model of CO2-Laser Engraver to ablation in poly(methyl methacrylate) - PMMA based on the effects of laser power and processing speed on the depth and width of microchannels Furthermore, successfully application Hexavalent Chromium in water – Colorimetric Method which can sense Cr6+ in stock solution of tap water with (R2 =0.9809) and determination Hexavalent Chromium in tap water was confirmed with 108 % (Spike

50 ppb) and 105 % ( Spike 100 ppb) showed that both of two volumes followed a positive direction for this research

ACKNOWLEDGEMENT

This thesis has been greatly conducted from the support as well as assistance of

many people whom I would sincerely like to give deep thanks here

First of all, I would like to express sincere thanks to the school board Thai

Nguyen University of Agriculture and Forestry, Faculty of International Training and

Development; Advanced Education Program, thank the teachers that have imparted to

me the knowledge and valuable experience during the process of learning and

researching here

In the process of implementing and completing thesis, I am deeply grateful to my

supervisor, Prof Yuh-Chang Sun at Department of Biomedical Engineering and

Environmental Science, National Tsing Hua University (NTHU), Taiwan who has

spent a lot of time, created favorable conditions, take care, generous and enthusiastic

to guide me In addition, I would like to say thanks to Ph.D Nguyen Huu Tho for his

enthusiasm in guiding and correcting my report writing

I sincerely thank Ph.D Tsung-Ting Shih, an enthusiastic guider, he was the one

who has had a very positive influence on me and my orientation from the beginning on

suggesting and assisting me this interesting topic during implementation of the study

I would gratefully like to thank Ping-Hung Chen, I couldn't gain new research

experiences and noticeably involve in a variety of fantastic work by practicing in

several new scientific instruments and chemically professional devices without him

He continued to inspire along the way as well as his enthusiastic and responsibility

I also want to thank Louise, Betty, Yuting-Luo and lovely friends in NTHU, all

of your presences would help my little heart experience the second home with

unforgettable memories and events

I would like to express my deep gratitude and motivation to my parents, my

family and my all friends for their encouragement throughout my studies

Ultimately, in the process of implementing the project, due my time and research

levels are limited so this project is inevitable shortcomings So, I would like to receive

the attention and feedback from teachers and friends to this thesis is more complete

I sincerely thank you!

Thai Nguyen, September 30th, 2015 Signature of Student:

Ta Thi Viet Nga

TABLE OF CONTENTS

LIST OF FIGURES 1

LIST OF TABLES 1

LIST OF ABBRIVIATIONS 2

I INTRODUCTION 3

1.1 Research rationale 3

1.2 Research’s objectives 4

1.3 Research questions 4

1.4 Limitations of the study 5

1.5 Definitions 5

1.5.1 Microfluidic 5

1.5.2 Microfluidic dilution chip 6

II LITERATURE REVIEW 7

2.1 Microfluidic dilution chip 7

2.2 Hexavalent Chromium in water – Colorimetric Method 11

III METHOD 15

3.1 Materials 15

3.1.1 Raw materials 15

3.1.2 The chemicals 16

3.1.3 Equipments 16

3.2 Method 19

3.2.1 Design microchannel on AutoCAD software for Engraving on PMMA sheet 19

3.2.2 Inspection of the channel 22

3.2.3 Creating the input on chip 25

3.2.4 Chip transplantation 25

3.2.5 NanoPort connections with microfluidic dilution chip 29

3.2.6 Verify of Microfluidic dilution chip operation with Rhodamine solution 30

3.2.7 Determination HexavalentChromium in tap water 32

IV RESULTS 35

4.1 Fabrication microchannels on PMMA by CO2-Laser Engraver 35

4.2 Effect of Speed and Power of CO2 laser on microchannels of chip 36

4.3 Verify of Microfluidic dilution chip’s Channel 37

4.4 Determination Hexavalent Chromium in tap water 39

V DISCUSSION AND CONCLUSION 41

5.1 Discussion 41

5.2 Conclusion 42

REFERENCES 44

LIST OF FIGURES

Figure 2.1 Diagram of a dilution chip sample 8

Figure 2.2 Schematic demonstrating the application of the formulas 9

Figure 2.3 Outlet Vertical Channel 10

Figure 3.1 Design microchannels on AutoCAD 2004 software 20

Figure 3.2 The complete designing microchannels on a PMMA sheet 20

Figure 3.3 Measuring channel by Power Image Analysis (PIA) systems 24

Figure 3.4 Schematic illustration of image’s result of SS-50 lens 24

Figure 3.5 Checking distance between countersink and point on the chip 25

Figure 3.6 Schematic illustration of all of layers is submerged by 26

Figure 3.7 Schematic illustration 26

Figure 3.8 Chip transplantation 28

Figure 3.9 Transplantation chip’s layers for placing into 28

Figure 3.10 Temperature control in Hot air circulation oven 29

Figure 3.11 NanoPort connections with microfluidic dilution chip of process 30 Figure 3.12 Verify of Microfluidic dilution chip’s Channel operation with 32

Figure 4.1 Schematic diagram of the photothermal ablation process 35

Figure 4.2 Microchannels in PMMA have been engraved 35

Figure 4.3 Effect of the laser power on depth and width 36

Figure 4.4 Size microchannels with the constant power 95 (%) and 37

Figure 4.5 Microfluidic dilution chip's channel was examined 38

LIST OF TABLES

Table 3.1: Items with the their Speed and Power number of percentage 21

Table 3.2: The Speed and Power numbers of percentage of channel 22

Table 4.1: Examination of tap water concentration 40

Table 4.2: Determination Hexavalent Chromium in tap water 40

LIST OF ABBRIVIATIONS

WHO : The World Health Organization

EPA : United States Environmental Protection Agency

MCL : Maximum contaminant level

AAS : Atomic absorption spectrometry

ICP-AES : inductively coupled plasma-atomic emission spectrometry

ICP-MS : Inductively coupled plasma-mass spectrometry

PMMA : Poly methyl methacrylate

PIA : Power Image Analysis

AVG : Average

SD : Standard deviation

I INTRODUCTION

1.1 Research rationale

Because of Industrialization, the World in general and Vietnam in particular is

focused on wastewater problems The main cause of heavy metal pollutants are

dumped into the environmental process industrial waste water and toxic waste water

untreated or treatment is not satisfactory The phenomenon of water has been

contaminated heavy metals in the water basin near industrial areas, big cities and

mining areas There is a growing public concern over the potential accumulation of

heavy metals in water, owing to rapid industrial development Like all other forms of

nature, water suffers from pollution This problem definitely is very important to

human in the world The concern over heavy metal in the water contamination stems

primarily from health risks, from direct contact with the contaminated water, and

vapors from the contaminants

The World Health Organization (WHO) recommends a maximum allowable

concentration of hexavalent chromium in drinking water is 0.05 milligrams per liter

In a September 2010 draft human health assessment for hexavalent chromium, EPA

proposed to classify hexavalent chromium as likely to be carcinogenic to humans

when ingested Hexavalent chromium is more toxic than trivalent chromium and

poses potential health risks People who use water containing total chromium in

excess of the maximum contaminant level (MCL) over many years could experience

skin rashes, upset stomachs and ulcers, respiratory problems, weakened immune

systems, kidney and liver damage, alteration of genetic material, lung cancer or

death Based on the above, the mount of chromium concentration in water is likely to

a serious problem for plant, organisms, environment, and etc However, the current

methods for the detection of Chromium, which is nothing more than the use of

atomic absorption spectrometer (atomic absorption spectrometry, AAS), Inductively

Coupled Plasma Atomic Emission Spectrometer (inductively coupled plasma-atomic

emission spectrometry, ICP-AES), inductively coupled plasma mass spectrometry

(Inductively coupled plasma-mass spectrometry, ICP-MS) and fluorescence assay

(fluorescent analysis), these methods often require expensive and bulky equipment

Not only that, the operator must receive professional training to operate Therefore,

establish simple and fast analytical techniques for the immediate detection at home,

company on tap water that will be convenient and helpful Thus, I propose Research:

“Rapid determination Hexavalent Chromium in tap water by using a Microfluidic dilution chip”

 What is the effect of laser power and processing speed on the depth and width

of microchannels from Poly methyl methacrylate (PMMA) for determining

their percentage for creating microfluidic dilution chip?

 What is effect of microfluidic dilution chip with Hexavalent Chromium in tap water?

1.4 Limitations of the study

Accordingly, the main purpose of study is to combine efficiently simple-tech

applications into scientific study at where we firstly focused on creating or producing

scientific instruments, at least simple stuffs, in order to lower cost and expense in

scientific researches to accelerate the possibilities and inspirations of study

Unfortunately, besides the possibility assessment of using microfluidic dilution chip

is firstly focused on putting chips into the Temperature Control, people must graft

chip carefully and correct techniques The second, there is limited study time that is

short However, it is not influence significantly to the widely using for rapid

production of microfluidic dilution chip with poly methyl methacrylate when

successfully conducted

1.5 Definitions

1.5.1 Microfluidic

Microfluidics is a multidisciplinary field intersecting engineering, physics,

chemistry, biochemistry, nanotechnology, and biotechnology, with practical

applications to the design of systems in which small volumes of fluids will be handled

and controlled, usually in the range of microliters (10-6 ) to picoliters (10-12).At least

one dimension of the channel is of the order of a micrometer or tens of micrometers in

order to consider it microfluidics Generally, when researchers speak of microfluidics,

they refer to man-made channels in networks of channels with lowest dimensions

from tens to hundreds micrometers Fluid flows in natural microchannels as blood

vessels or plants capillaries are mostly excluded from microfluidics

1.5.2 Microfluidic dilution chip

A microfluidic dilution chip is a set of micro-channels etched or molded into a

material (glass, silicon or polymer such as PDMS, PMMA) The micro-channels

forming the microfluidic dilution chip are connected together in order to achieve a

desired function (mix, pump, redirect and/or allow chemical reactions in a cell)

This network of microchannels trapped in the microfluidic dilution chip is

connected to the outside by inputs and outlets pierced through the chip, as an interface

between the macro and micro-world It is through these holes that the liquids (or gas)

are injected and removed from the microfluidic dilution chip (through tubing, syringe

adapters or even free holes in the chip)

II LITERATURE REVIEW

2.1 Microfluidic dilution chip

Over the period of two decades, scientists studied the microfluidic system and

expanded its application in human life At that time, creating a large number of silicon

substrate (single-crystal silicon, glass, quartz, and so on) as material production wafer

However, despite high chemical inertness, good stability and technological process

was quite mature, but must meet the demands of high-tech equipment such as raw

materials in Microelectromechanical Systems (MEMS) manufacturing process, so that

cost was quite expensive, leading to its market value was more unsatisfactory

A study conducted in 2000 by George (George et al, 2000) who discovered and

studied the important issue which the channels of a microfluidic dilution chip have

achieved results ideally after dilution process inside microfluidic dilution chip with a

new gradient concept This direction has oriented a new domain that depends on

gradients in concentration Additionally, the method is experimentally simple and

highly adaptable, and requires no special equipment except for an elastomeric relief

structure that can be readily prepared by rapid prototyping They used a network of

microchannels having three inlets Two syringes (contained solutions of chemicals of

different concentrations) were connected with two inlets (Stephan et al, 2000)

However, if a diluted follows this model, when the concentration gradient of

microchannels as the number increases, the system will become too complicated and a

concentration gradient is no longer stable (Figure 2.1)

(a) Scheme of the PDMS microfluidic gradient generator used in this work

(b) Schematic design of a representative gradient-generating microfluidic network

Solutions containing different chemicals were introduced from the top inlets and

allowed to flow through the network The fluid streams were repeatedly combined,

mixed, and split to yield distinct mixtures with distinct compositions in each of the

branch channel When all the branches were recombined, a concentration gradient was

established across the outlet channel

(c) Equivalent electronic circuit model of the pyramidal microfluidic network (George

et al., 2000)

In addition, a study conducted in 2000 by George (George et al, 2001) who

extended his research, used laminar flow to generate gradients should be useful in both

biological and nonbiological research Appropriately designed networks of

microchannels for controlled diffusive mixing of sub- stances generated a range of

shapes for the gradients, including linear, parabolic, and periodic But to avoid the

complexity of the channels of the chip, they calculated and towards a simple dilution

system more (Figure 2.2) The concentrations at the end of the serpentine channels can

be calculated by multiplying the concentration of the incoming streams (Cp, Cq, Cr)

with the corresponding numbers of the splitting ratio ((Vp + 1)/B,(B– Vq)/B, (Vq+

1)/B, and (B– Vr)/B, as indicated) (Daniel et al, 2001)

Figure 2.2 Schematic demonstrating the application of the formulas

(George et al., 2001)

Gradients across channels, which were been changed by width and depth

Furthermore, Gradients being extended over several hundreds of micrometers are

stable over long periods of time, since diffusion is a slow process on the millimeter

scale Therefore, George and his colleagues to spend more time to study this proposal

gave calculated for a new gradient concept but unresolved a problem, which is losing

of time when performing experiments (George et al, 2001)

On the other hand, with a study related to the gradient generation, there is the

device only had 2 inputs Microdevices were micromachined (CNC milling) directly

into PMMA sheets From this research, using PMMA was good idea (Hayat et al,

2008) Although, they were not improved the instrumentation, modified the designs for

higher throughput applications, and studied effect of inlet variables on diluter systems

Until 2009, they continued to study to more complete his research They base on the

basic principle for generating linear concentration gradients was originally described

by Gorge and Co-workers (Gorge et al, 2001) Furthermore, in microscopic

dimensions, the Reynolds number of the fluid is very small, the liquid mixing can be

performed by diffusion, in order to solve the fluid can’t been effectively mixed in a

flow path leading to the concentration gradient deviation The experimental results

were assessed to be good from theory to actual survey with the model The developed

networks are proven to deliver precise linear concentration gradients (R2 = 0.9973 and

0.9991) (Yusuf et al, 2009)

Figure 2.3 Outlet Vertical Channel (Hayat et al, 2009)

The figure 2.3 showed the performance of the conventional resistive network

design, at a flow rate of 0.1 mL/s per inlet: The entire concentration distribution and linearity test for each level of the network, represented by the means and standard

error of the means (SEM) for four different experiments, in comparison with the

analytical model (Robert et al, 2009) Two syringe pumps were connected to the

microfluidic device through two syringes We could not be denied in terms of its mixing efficiency, active design are generally better than passive, because the former

are required to be combined with other additional devices to provide the energy

needed to drive element, coupled with the production often requires very sophisticated

technology required before construction of the movable element or the disturbance

generator, for this study uphold the production of simple, low cost and so were all

contradict the original intention (Nick et al, 2009) Therefore, future research will

continue to decline passive combiner design for the spindle, the desired wafer by

appropriate acquired a well-designed solution mixing efficiency (Yusuf et al, 2008)

2.2 Hexavalent Chromium in water – Colorimetric Method

According the National Institute of Environmental Analysis (NIEA) of Taiwan

(1998) a scientific paper was published about Hexavalent Chromium in water –

Colorimetric method

- Research’s scope:

This method is suitable for drinking water, drinking water, surface water,

groundwater, effluents and waste (sewage) quality with amount of hexavalent

chromium concentration in water testing

- Method:

In acidic solution, hexavalent chromium and diphenyl urea diamine (1.5 -

Diphenylcarbazide) purple reaction substance in the spectrophotometer at a

wavelength of 540 nm at measuring the absorbance and quantified

- Interference:

 If: [ Fe 3+ ] ≥ 1 (mg / L) Although in certain wavelengths will

Absorb values which are not the degree of interferences

[ Mo6+ ] ≥ 200 (mg / L) or [ Hg2+ ] ≥ 200 ( mg / L)

It will interfere, but within the extent of hexavalent molybdenum or mercury salt in the pH range of the method specified interference is not high Also if

such interference hexavalent molybdenum, vanadium salts, iron, copper ions in

water samples can be extracted by chloroform produced these metals copper

and iron compounds (Cupferrates) and remove it, but the residue of chloroform

in water samples and copper and iron mixture (Cupferron) available acid

 Analytical balance: You can fine scales to 0.1 mg

 Pipette or the automatic corrected pipette

- Reagent

 Reagent water: resistivity ≧ 16 MΩ - cm

 0.5 M sulfuric acid solution diluted with distilled water 3 M sulfuric acid solution of 83.3 mL to 500 mL

 Diphenyl urea ammonia solution: Dissolve 0.25 g diphenyl ammonia urea a

50 mL acetone (Acetone), stored in a brown bottle, such as discoloration of

the solution should disuse

 Concentrated of phosphoric acid

 Concentrated of sulfuric acid: 9 M and 3 M

 Chromium stock solution: In 1000 mL volumetric flask, dissolve 0.1414 g

of potassium dichromate (K2Cr2O7) in distilled water, dilute to the mark:

1.0 mL equivalent to Cr (0.05 mg) After confirmed by the concentration of

commercial illustration and attach the shelf life of standard stock solution

 Chromium standard solution: in 100 mL volumetric flask, dilute 10.0

mL stock solution of chromium to the mark; 1.0 mL equivalent to Cr

(0.005 mg)

- Sampling and storage:

Collect at least 300 mL of water samples in plastic bottles, at 4 ℃ dark

refrigerated shelf life of 24 hours

- Water sample processing and measurement:

 Take been appropriately diluted or raw water sample 47 mL in an appropriate container, add about 0.12 mL of concentrated phosphoric acid,

and then to 0.5 M sulfuric acid solution and a pH meter, adjust the pH of

water samples to 2.0 ± 0.5

 Add 1.0 mLdiphenyl urea ammonia solution, mix well and pour into 50 mL volumetric flask, dilute with reagent water to 50 mL Stand 5 to 10 minutes

to read the absorbance in a spectrophotometer at 540 nm wavelength, with

reagent water as the control sample, absorbance readings shall be deducted

prepared blank absorbance by the calibration curve obtained by hexavalent

chromium concentrations (mg / L)

- Processing results

From the absorbance of the sample solution measured, on behalf of the

calibration curve can be obtained solution of hexavalent chromium

concentration (mg / L), and then according to the following hexavalent

chromium concentration in the sample We have formula:

A = A'× F

A: The hexavalent chromium concentration in the sample (mg / L)

A': from the calibration curve of the concentration of hexavalent chromium

in the sample solution (mg / L) is obtained

F: dilution

III METHOD

3.1 Materials

3.1.1 Raw materials

Poly (methyl methacrylate) PMMA sheet (Size: 350 mm (Length) × 200 mm

(Width) × 2 mm (Height)) was purchased Manufacturers: Kun Quan Engineering

Plastics Co Ltd., Hsinchu, Taiwan Binder clip (Size: Type 1: 32mm; Type 2: 51 mm)

was purchased Manufacturers: No.157, Shihpin Rd., East District, Hsinchu City

30062, Taiwan Glasses (Size: 100 mm (Length) × 75 mm (Width) × 3 mm (Height))

was purchased Manufacturers: No 36, Sida Rd., East District, Hsinchu City 30062,

Taiwan Kimwipes Kimtech Paper (Size: 21 cm (Length) × 11 cm (Width)) was

purchased Manufacturers: Made in USA of U.S.and/or non – US Materials/Fabriqué

aux États – Unis à partir de materiauxprovenant des États – Unisou d’ ailleurs

Distributed in the U.S by Kimberly – Clark Global Sale, LLC, Roswell, GA 30076 –

2199 Anti-acid corrosion instant glue was purchased Manufacturers: Luotai

Enterprises Ltd - Loctai Enterprise Co Ltd., Hsinchu, Taiwan.PEEK - poly

(Aryletherketone)tubings (Size: Diameter = 0.75 mm) was purchased Manufacturers:

Heng Yi Enterprises Limited - Heng Yi Enterprise Co Ltd., Taipei, Taiwan NanoPort

Bonding was purchased Manufacturers: IDEX Health & Science LLC Home of

Upchurch Scientific Products Oak Harbor, WA Nitrogen gas flask was purchased

Manufacturers: Chiah Lung Enterprise CO., LTD – NO 209, Sec.3ChuaHwa Rd

Hsinhu City, Taiwan

3.1.2 The chemicals

All the chemicals are used as receive without further treatment Deionized water – DIW - Deionized water (deionized water, 18.2 MΩ.cm) was obtained using a Milli-

Q apparatus (Millipore, Bedford, MA, USA).Ethanol – C2H5OH( 95%) was purchased

Manufacturers: No 16, Toufen Township, Miaoli County 35145, Taiwan.Phosphoric

acid – H3PO4 (Crystalline, ≥ 99.999% trace metals basis ) Product of Switzerland:

Sigma – Aldrich, Co., 3050 Spruce Street, St.Louis, MO 63103 USA 314 – 771 –

5765.1.5 – Diphenylcarbazide (Reag Ph Eur., ≥ 98.0%, for metal titration ) Product

of Switzerland: Sigma – Aldrich, Co., 3050 Spruce Street, St.Louis, MO 63103 USA

314 – 771 – 5765.Acid sulfuric – H2SO4 Product of Switzerland: Sigma – Aldrich,

Co., 3050 Spruce Street, St.Louis, MO 63103 USA 314 – 771 – 5765

Acetone-(CH3)2CO was purchased Avantor Performance Material Lnc 3477 corporate

Parkway, Suite 200 center Valley, PA 18034 ( 610 – 573 – 2600 )

3.1.3 Equipments

a Carbon dioxide laser system

- Carbon dioxide laser micromachining system, LES-10, air-cooled metal pipe

carbon dioxide laser, a work area 355.6 × 203.2 mm, maximum engraving

- Carbon dioxide laser engraving machine (CO2-Laser Engraver):

Engraving system used in this experiment the carbon dioxide laser Carbon

dioxide laser machining schematic two-dimensional of micro-structure, the

outlet wavelength of 10.6 μm infrared Working principle is the use of high

power density laser beam as a heat source, the laser light is focused by the lens

surface of the substrate, while the release of energy, this energy can be

generated on the substrate surface hot spots (Hot spot), and transmitted through

the heat conduction inside the base, when the boiling point of the hot energy of

Scient material will cause the substrate vaporized into monomers In addition,

scan rate and the number of scans on a substrate depict the depth and

configuration of different road

b Microplate Spectrophotometers

Manufacturers: Tecan Austria GmbH Untersbergstrasse 1A - A -5082

Grödig/Salzburg AUSTRIA/EUROPE: Microplate spectrophotometers, also called

microplate readers, allow researchers to analyze multiple samples in parallel using 6-

to 1536-well formats, as opposed to single sample measurements Instrument design,

user interface capabilities, and cost play key roles in purchasing a suitable microplate

reader Spectrophotometer detection parameters are principally UV (ultraviolet),

UV/Vis (ultraviolet/visible), or fluorescence absorbencies

c Some other equipments

Power Image Analysis (PIA) system: High-resolution optical imaging

microscope (high resolution optical microscope, FS-880ZU, 140X-880X optical

continuous zoom, color high-resolution 1.3-megapixel image sensor), measurement-bit

digital microscopy platform (maximum vertical movement range of 13 mm) Image

analysis software measurement (PIA): King Hing Computer Technology Co., Ltd

(ChingHsing Computer-Tech Ltd., Taipei, Taiwan) Image analysis software (ImageJ

software) downloaded from http://rsbweb.nih.gov/ij/index.htmL Desktop drill: (multi

drilling machines) LT-848, shaft speed 10 000 rpm Hot air circulation oven: (DK-45,

RT + 5°C - 300°C, resolution 0.1°C) Manufacturers: Wing Yan Limited (Yeong Shin

Co Ltd., Hsinchu, Taiwan) The electric drill press is a universal drill mount with a

metal quick-release clamp that accommodates 05-6.5mm drills This desktop drill

press horizontal mounting capability converts drills into a bench top tool that's ideal

for grinding, buffing and sanding applications, as well as for flex shaft operations

Ultrasonic cleaner: Transonic Digital D-7700, Elma GmbH & Co KG, Singen,

Germany Manufacturers: Guohong Technology Co., Ltd - Kou Fua Technology Co

Ltd., Taipei, Taiwan Ultrasonic cleaning is to be the most efficient method of

removing contaminants; such as fingerprints, oxides and other deposits from visible

and invisible surfaces, holes and cracks In general, if an item can be cleaned with

liquid, it can be cleaned much faster and more thoroughly with an ultrasonic cleaner

Hot air circulation oven: DK-45, RT + 5°C-300°C, resolution 0.1°C.Manufacturers:

Wing Yan Limited -Yeong Shin Co Ltd., Hsinchu, Taiwan The temperature control

adopts the auto electronic horizontal circulating heating to effect of creating chip

device Syringe pump: Syringe infusion pump, KDS-100, Scientific Instrument

Service, Ringoes, NJ, USA Manufacturers: Dan Enterprises Limited (Scientific

Hightek Co Ltd., Taipei, Taiwan)