- Taipei, T'ai-pei, Taiwan
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A digital microfluidic modular interface (chip-to-chip interface) which possesses an electrode with an orifice to vertically transport core–shell droplets is presented. The electrodes were geometrically designed to promote droplet... more
A digital microfluidic modular interface (chip-to-chip interface) which possesses an electrode with an orifice to vertically transport core–shell droplets is presented. The electrodes were geometrically designed to promote droplet deformation and suspension. The droplets were then applied with an electrical potential for insertion into and passage through the orifice. The concepts were tested with three types of droplets at the volume of 0.75~1.5 μL, which is usually difficult to transfer through an orifice. The integration of electrowetting on dielectric (EWOD) with paper-based microfluidics was demonstrated: the droplet could be transported within 10 s. More importantly, most of the core droplet (~97%) was extracted and passed through with only minimal shell droplets accompanying it.
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Paper-based technologies have been drawing increasing attentions in the biosensor field due to their economical, ecofriendly, and easy-to-fabricate features. In this paper, we present a time-delay valve mechanism to automate a series of... more
Paper-based technologies have been drawing increasing attentions in the biosensor field due to their economical, ecofriendly, and easy-to-fabricate features. In this paper, we present a time-delay valve mechanism to automate a series of procedures for conducting competitive enzyme-linked immunosorbent assay (ELISA) on a paper-based device. The mechanism employs a controllable time-delay valve, which has surfactants to dissolve the hydrophobic barriers, in a fluid pathway. The valves can regulate the liquid and sequentially deliver the sample flow for automating ELISA procedures in microchannels. Competitive ELISA is achieved in a single step once the sample, or small molecule pesticide (e.g., Imidacloprid), is applied onto the paper-based device with a comparable sensitivity to plate-based competitive ELISA. The results further demonstrate the appositeness of using paper-based devices with the valve designs for on-the-go ELISA detection in agriculture and biomedical applications.
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Uniform silicon nanowires (SiNW) were successfully fabricated on the top, bottom, and sidewall surfaces of silicon microchannels by using a two-step electroless etching process. Different microchannel patterns with the channel width from... more
Uniform silicon nanowires (SiNW) were successfully fabricated on the top, bottom, and sidewall surfaces of silicon microchannels by using a two-step electroless etching process. Different microchannel patterns with the channel width from 100 to 300 μm were first fabricated in a 10 mm × 10 mm silicon chip and then covered by SiNW with an average height of 10–20 μm. The effects of the microchannel geometry, micro/nano-hierarchical structures on pool boiling were studied and the bubble dynamics on different sample surfaces were compared. It was found that the combination of the micro/nanostructures promoted microbubble emission boiling under moderate heat fluxes, and yielded superior boiling heat transfer performance. At given wall superheats, the maximum heat flux of the microchannel with SiNW was improved by 120% over the microchannel-only surface, and more than 400% over a plain silicon surface. These results provide a new insight into the boiling mechanism for micro/nano-hierarchic...
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Point-of-care (POC) tests capable of individual health monitoring, transmission reduction, and contact tracing are especially important in a pandemic such as the coronavirus disease 2019 (COVID-19). We develop a disposable POC cartridge... more
Point-of-care (POC) tests capable of individual health monitoring, transmission reduction, and contact tracing are especially important in a pandemic such as the coronavirus disease 2019 (COVID-19). We develop a disposable POC cartridge that can be mass produced to detect the SARS-CoV-2 N gene through real-time quantitative polymerase chain reaction (qPCR) based on digital microfluidics (DMF). Several critical parameters are studied and improved, including droplet volume consistency, temperature uniformity, and fluorescence intensity linearity on the designed DMF cartridge. The qPCR results showed high accuracy and efficiency for two primer-probe sets of N1 and N2 target regions of the SARS-CoV-2 N gene on the DMF cartridge. Having multiple droplet tracks for qPCR, the presented DMF cartridge can perform multiple tests and controls at once.
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Abstract—A simulation program is developed which is capable of calculating the output responses of piezoresistive pressure sen-sors as a function of pressure and temperature. Analytical models based on small and large deflection theories... more
Abstract—A simulation program is developed which is capable of calculating the output responses of piezoresistive pressure sen-sors as a function of pressure and temperature. Analytical models based on small and large deflection theories have been applied to predict the sensitivity and linearity of pressure sensors. Surface-micromachined diaphragms with square or circular shapes, fabri-cated by a low pressure chemical vapor deposition sealing process, are designed and tested to verify the program. They are made of polysilicon and have a standard width (diameter) of 100 m and thickness from 1.5 to 2.2 m. Various parameters of the piezoresistive sensing resistors, including length, orientation, and dopant concentration, have been derived and constructed on top of the diaphragms. For a 100-m-wide 2-m-thick square-shape pressure sensor, calculated and experimental results show that sensitivity of 0.24 mV/V/(lbf/in2) is achieved. Experimentally, a maximum linearity error of 0.1 % full-sc...
Research Interests: Materials Science, Microelectromechanical systems, Chemical Vapor Deposition, SEM, Micromachining, and 13 moreResistance, Process Design, Si, Systems, CVD, Shape, Sensitivity, Analytical Model, Pressure Sensor, Linearity, Low Pressure Boiler, Electrical And Electronic Engineering, and Pressure Sensors
A novel single nucleotide polymorphisms (SNPs) detection scheme was proposed by conducting melting analysis on microbeads. These beads were utilized to immobilize target DNA duplex, and flowing through a well-controlled... more
A novel single nucleotide polymorphisms (SNPs) detection scheme was proposed by conducting melting analysis on microbeads. These beads were utilized to immobilize target DNA duplex, and flowing through a well-controlled temperature-gradient region in microchannels on a microfluidic chip. As the microbeads going through from low temperature regions to high temperature regions, the DNA duplex denatured and the intercalated fluorescent dyes were released, inducing the fluorescent signals to decay. The melting curves were then acquired for SNP genotyping. Different genotypes (i.e. wild and mutant types) with a SNP location of Ataxia Telangiectasia-Mutated (ATM) genes from Landrace sows were tested and successfully discriminated.
We presents a microinjection system for gene delivery to planarian. The system consists of two parts: a planarian-fixing platform, which provides a low-temperature environment to make planarian become motionless for injection, and a... more
We presents a microinjection system for gene delivery to planarian. The system consists of two parts: a planarian-fixing platform, which provides a low-temperature environment to make planarian become motionless for injection, and a nanoliter injector (nanoliter-scale microinjector). The system is tested by injecting fluorescent microbeads and gene (e.g. dsRNA) respectively into planarian. In particular, successful delivery of DjAg02 dsRNA leads to a reduction of DjAg02 expression, which results in a degenerated phenotype of planarian. The results show our system as an alternative to traditional gene delivery (i.e. ingestion, which performs delivery by feeding planarian genetic substances mixed food). Our system is applicable to studying the function of genes related to starvation condition. Additionally, the dosage of genetic substances is consistent, which is required for the following analyses.
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A microfluidic chip, which can separate and enrich leukocytes from whole blood, is proposed. The chip has 10 switchback curve channels, which are connected by straight channels. The straight channels are designed to permit the inertial... more
A microfluidic chip, which can separate and enrich leukocytes from whole blood, is proposed. The chip has 10 switchback curve channels, which are connected by straight channels. The straight channels are designed to permit the inertial migration effect and to concentrate the blood cells, while the curve channels allow the Dean flow to further classify the blood cells based on the cell sizes. Hydrodynamic suction is also utilized to remove smaller blood cells (e.g., red blood cell (RBC)) in the curve channels for higher separation purity. By employing the inertial migration, Dean flow force, and hydrodynamic suction in a continuous flow system, our chip successfully separates large white blood cells (WBCs) from the whole blood with the processing rates as high as 1 × 108 cells/sec at a high recovery rate at 93.2% and very few RBCs (~0.1%).
Recent advancement in microfabrication has enabled the implementation of implantable drug delivery devices with precise drug administration and fast release rates at specific locations. This article presents a membrane-based drug delivery... more
Recent advancement in microfabrication has enabled the implementation of implantable drug delivery devices with precise drug administration and fast release rates at specific locations. This article presents a membrane-based drug delivery device, which can be electrically stimulated to release drugs on demand with a fast release rate. Hydrogels with ionic model drugs are sealed in a cylindrical reservoir with a separation membrane. Electrokinetic forces are then utilized to drive ionic drug molecules from the hydrogels into surrounding bulk solutions. The drug release profiles of a model drug show that release rates from the device can be electrically controlled by adjusting the stimulated voltage. When a square voltage wave is applied, the device can be quickly switched between on and off to achieve pulsatile release. The drug dose released is then determined by the duration and amplitude of the applied voltages. In addition, successive on/off cycles can be programmed in the voltag...
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To develop and realize the personalized medicine and point-of-care in genetic testing, the sequences of DNA extraction process should be integrated. This thesis introduces the implementation of magnetic beads (MB) based DNA extractions on... more
To develop and realize the personalized medicine and point-of-care in genetic testing, the sequences of DNA extraction process should be integrated. This thesis introduces the implementation of magnetic beads (MB) based DNA extractions on electrowetting on electrowetting-based digital microfluidics (DMF). The reagents are DNA extraction kit. They are characterized as a droplet on DMF. These droplets can be precisely manipulated by electric signals, which simplifies the whore genetic testing. The result from the on-chip DNA of extraction are validated by SYBR® GREEN 1. DNA is successfully extracted from 90nl whole blood. Finally, our EWOD chip has been optimized in the following three aspects: (1) it has independent paths of the electrodes for different reagent to avoid the cross-contamination problem. (2) It utilizes MBs to replace the complex centrifugation in tradition DNA extraction procedures. (3) Ratio separation electrodes are designed to re-suspend the MBs and to improve the ...
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A microfluidic chip is proposed to separate microparticles using cross-flow filtration enhanced with hydrodynamic focusing. By exploiting a buffer flow from the side, the microparticles in the sample flow are pushed on one side of the... more
A microfluidic chip is proposed to separate microparticles using cross-flow filtration enhanced with hydrodynamic focusing. By exploiting a buffer flow from the side, the microparticles in the sample flow are pushed on one side of the microchannels, lining up to pass through the filters. Meanwhile a larger pressure gradient in the filters is obtained to enhance separation efficiency. Compared with the traditional cross-flow filtration, our proposed mechanism has the buffer flow to create a moving virtual boundary for the sample flow to actively push all the particles to reach the filters for separation. It further allows higher flow rates. The device only requires soft lithograph fabrication to create microchannels and a novel pressurized bonding technique to make high-aspect-ratio filtration structures. A mixture of polystyrene microparticles with 2.7 μm and 10.6 μm diameters are successfully separated. 96.2 ± 2.8% of the large particle are recovered with a purity of 97.9 ± 0.5%, while 97.5 ± 0.4% of the small particle are depleted with a purity of 99.2 ± 0.4% at a sample throughput of 10 μl/min. The experiment is also conducted to show the feasibility of this mechanism to separate biological cells with the sample solutions of spiked PC3 cells in whole blood. By virtue of its high separation efficiency, our device offers a label-free separation technique and potential integration with other components, thereby serving as a promising tool for continuous cell filtration and analysis applications.
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We present a low-potential method to control surface roughness of doped polypyrrole through redox-induced transformation in surface morphology. By varying the electric potential of as-deposited doped polypyrrole in aqueous sodium... more
We present a low-potential method to control surface roughness of doped polypyrrole through redox-induced transformation in surface morphology. By varying the electric potential of as-deposited doped polypyrrole in aqueous sodium dodecylbenzene sulfonate (0.1M) from -0.6 to +1.5V (vs. Ag/AgCl), doped polypyrrole transforms from being a hydrophilic film (60deg contact angle) to a hydrophobic film (107deg contact angle). Atomic force microscope
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ABSTRACT In this paper we present data of protein adsorption on topographically altered active polymeric films, investigated using atomic force microscopy (AFM), fluorescence microscopy, and contact angle measurement. The surface... more
ABSTRACT In this paper we present data of protein adsorption on topographically altered active polymeric films, investigated using atomic force microscopy (AFM), fluorescence microscopy, and contact angle measurement. The surface wettability of biocompatible polypyrrole (PPy) films was altered via low applied currents, and we have demonstrated switchable hydrophobic-hydrophilic surfaces, used as protein adhesion substrates. The preliminary results showed that both BSA and fibronectin have higher affinities for and adhere preferentially to hydrophobic surfaces.
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A continuous-flow microchip with a temperature gradient in microchannels was utilized to demonstrate spatial melting analysis on microbeads for clinical Single Nucleotide Polymorphisms (SNPs) genotyping on animal genomic DNA. The chip had... more
A continuous-flow microchip with a temperature gradient in microchannels was utilized to demonstrate spatial melting analysis on microbeads for clinical Single Nucleotide Polymorphisms (SNPs) genotyping on animal genomic DNA. The chip had embedded heaters and thermometers, which created a rapid and yet stable temperature gradient between 60 °C and 85 °C in a short distance as the detection region. The microbeads, which served as mobile supports carrying the target DNA and fluorescent dye, were transported across the temperature gradient. As the surrounding temperature increased, the fluorescence signals of the microbeads decayed with this relationship being acquired as the melting curve. Fast DNA denaturation, as a result of the improved heat transfer and thermal stability due to scaling, was also confirmed. Further, each individual microbead could potentially bear different sequences and pass through the detection region, one by one, for a series of melting analysis, with multiplex, high-throughput capability being possible. A prototype was tested with target DNA samples in different genotypes (i.e., wild and mutant types) with a SNP location from Landrace sows. The melting temperatures were obtained and compared to the ones using a traditional tube-based approach. The results showed similar levels of SNP discrimination, validating our proposed technique for scanning homozygotes and heterozygotes to distinguish single base changes for disease research, drug development, medical diagnostics, agriculture, and animal production.
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ABSTRACT A new technique is developed to directly grow Cu nanowire (CuNW) on Si substrate with electro-chemical deposition to produce height-controlled hydrophilic nanowired surfaces for enhancing pool boiling performance. For broader... more
ABSTRACT A new technique is developed to directly grow Cu nanowire (CuNW) on Si substrate with electro-chemical deposition to produce height-controlled hydrophilic nanowired surfaces for enhancing pool boiling performance. For broader heat transfer applications, CuNW and Si nanowires (SiNW) with various nanowire heights were fabricated and examined under pool boiling with water. The heat transfer performance of the samples with NW arrays is enhanced with increasing NW heights regardless of the NW materials. The surface with the tallest NW structure (35 μm-tall SiNW) yielded a heat flux of 134 W/cm2 at 23 K wall superheat, about 300% higher than a plain Si surface at the same wall superheat.Highlights► A new technique is developed to directly grow copper nanowire on silicon substrate. ► Increasing nanowire height improves boiling performance. ► Optimal results were obtained in pool boiling with 35 nm long nanowires.
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ABSTRACT We report the fabrication of a plasma-generating device on a paper substrate. This device was fabricated using a screen print process. Plasmas were ignited between two parallel electrodes with a plasma gap of 237 to 710 μm using... more
ABSTRACT We report the fabrication of a plasma-generating device on a paper substrate. This device was fabricated using a screen print process. Plasmas were ignited between two parallel electrodes with a plasma gap of 237 to 710 μm using a dc power source. We demonstrated that a stable helium plasma can be sustained when the substrate is flat, rolled, and folded along various orientations. When the plasma was ignited with a 0.2-μL salt solution droplet with 1.4, 4.6, and 7.8 ng of Li, Na, and K respectively applied to the discharge gap, clear metallic emission lines emanated from the plasma. Our result demonstrates that this paper-based plasma device can be used in analytical applications.
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ABSTRACT Uniform SiNW structures were fabricated for the first time on the top, bottom and sidewall surfaces of microchannel heat sinks by using a two-step electro-less etching process. The micro/nano hierarchical structure yields... more
ABSTRACT Uniform SiNW structures were fabricated for the first time on the top, bottom and sidewall surfaces of microchannel heat sinks by using a two-step electro-less etching process. The micro/nano hierarchical structure yields superior boiling heat transfer performance. Its maximum heat flux is improved by 150% over the microchannel-only heat sink and 400% over a plain silicon surface. These results provide a new insight into the boiling mechanism for microchannel heat sinks using hierarchical structures.
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This paper presents a simple means that utilizes surface tension gradient to cause droplet deformation, and to tilt micro-objects. Thermocapillary or Marangoni effect, and contact angle hysteresis are employed to control the droplet shape... more
This paper presents a simple means that utilizes surface tension gradient to cause droplet deformation, and to tilt micro-objects. Thermocapillary or Marangoni effect, and contact angle hysteresis are employed to control the droplet shape and position. The device consists of a microplate placed onto a microdroplet, and can produce a 6.5deg tilting angle when actuated at 30 V. It shows
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ABSTRACT Country-Specific Mortality and Growth Failure in Infancy and Yound Children and Association With Material Stature Use interactive graphics and maps to view and sort country-specific infant and early dhildhood mortality and growth... more
ABSTRACT Country-Specific Mortality and Growth Failure in Infancy and Yound Children and Association With Material Stature Use interactive graphics and maps to view and sort country-specific infant and early dhildhood mortality and growth failure data and their association with maternal
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ABSTRACT A taxel device on flexible substrates based on the electrical contact resistance (ECR) variation mechanism is developed. The proposed taxel device consists of one top and one bottom substrates, which are coated with conductive... more
ABSTRACT A taxel device on flexible substrates based on the electrical contact resistance (ECR) variation mechanism is developed. The proposed taxel device consists of one top and one bottom substrates, which are coated with conductive polymer then face-to-face assembled. The device is tested with different substrate materials to show the viability of the ECR variation mechanism. It is found that when paper is used as the substrate material, because of its exclusive features of surface roughness and material compressibility, the ECR variation mechanism is greatly enhanced and the device exhibits higher sensitivity and larger working pressure range. Practical applications are investigated in elasticity measurement on phantom samples and biological tissues. The results are promising with our taxel device made on flexible substrates being capable of integration onto surgical tools and the potential to realize the psychical property of biological tissues.
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Articulated micro-fingers have been developed as an important building block to construct micro-robotic end-effectors such as a micro-hand. This micro-finger features robust finger segments made from bulk silicon, pneumatically driven... more
Articulated micro-fingers have been developed as an important building block to construct micro-robotic end-effectors such as a micro-hand. This micro-finger features robust finger segments made from bulk silicon, pneumatically driven balloon joints made of Parylene thin film, and monolithic integration to minimize leakage. We present the device concept, joint mechanism, and fabrication processes, as well as test results. For the current specification, each finger is measured to exert over 0.15 mN at 120 psi.
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ABSTRACT Doped polypyrrole coatings of varying degrees of wetting characteristics were prepared by a one-step anodic polymerization process and subsequently subjected to external applied potentials in an aqueous sodium... more
ABSTRACT Doped polypyrrole coatings of varying degrees of wetting characteristics were prepared by a one-step anodic polymerization process and subsequently subjected to external applied potentials in an aqueous sodium benzenedodecylsulfonate solution. When an applied potential was increased from −0.9 to +0.9 at steps of 300 mV for 300 s at each step, static contact angles gradually increased from 64° to 122°. The surface morphology of as-deposited polypyrrole was observed to transform from being nodular to an increasingly rough surface composed of microscale islands with nanoscale roughness, forming a micro/nanoscale hierarchical structure. The average roughness of these microscale islands were measured to be 2.3 nm at −0.8 V, which increased to 14.6 nm at +0.8 V, compared to the average roughness of doped polypyrrole at 4.8 nm. These microscale islands were oblong in shape, and their sizes increased as the applied potential increased. Changes in the average roughness resulted in a change in the surface wettability of polypyrrole—as-deposited polypyrrole showed a static contact angle of 90°, however, it lowered to 70° at −0.8 V and irreversibly increased to 115° at +0.8 V.
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This paper elucidates the extent of changes in surface wettability as influenced by the surface topography on a conducting polymer, polypyrrole. As-deposited, anion-doped polypyrrole is subjected to a series of incremental redox... more
This paper elucidates the extent of changes in surface wettability as influenced by the surface topography on a conducting polymer, polypyrrole. As-deposited, anion-doped polypyrrole is subjected to a series of incremental redox potentials ranging from -0.6 V to +1.5 V (vs. Ag/AgCl), and its surface properties are examined via SEM, AFM, and contact angle measurements. A causal relationship is found