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ABSTRACT: In this paper miniaturized disposable micro/nanofluidic components applicable to bio chip, chemical analyzer and biomedical
monitoring system, such as blood analysis, micro dosing system and cell experiment, etc are reported. This system includes
various microfluidic components including a micropump, micromixer, DNA purification chip and single-cell assay chip. For low
voltage and low power operation, a surface tension-driven micropump is presented, as well as a micromixer, which was implemented
using MEMS technology, for efficient liquid mixing is also introduced. As bio-reactors, DNA purification and single-cell assay
devices, for the extraction of pure DNA from liquid mixture or blood and for cellular engineering or high-throughput screening,
respectively, are presented.
Biotechnology and Bioprocess Engineering 04/2012; 9(2):86-92. · 1.28 Impact Factor
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ABSTRACT: This paper presents a dual-shank neural probe integrated with double-waveguides on each shank, which enables both optical stimulation and electrical recording. Two 15-μm-thick polymeric (SU-8) waveguides on each neural probe shank have been precisely defined by photolithography with a width of 24 μm and a spacing of 10 μm. The waveguides transmit a light coupled from optical fibers which are placed in the grooves located at the neural probe body. Each shank has 8 iridium recording electrodes which have the area of 11 μm × 13 μm. In front of each waveguide, four recording sites are deployed with a pitch of 100 μm. Blue light (473 nm in wavelength) has been successfully transmitted to the stimulation sites located at the end of the fabricated neural probe tips.
Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 08/2011; 2011:5480-3.
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ABSTRACT: We implement and characterize a 1.5 V 120 nW CMOS programmable monolithic reference generator for wireless implantable system. The proposed generator is optimized to be tolerable for power supply variation in a small area with programmability to generate various reference voltages and currents. The measured power line sensitivity are 0.02 / 1.1%/V for voltage and current reference, respectively. This reference generator can operate for input voltage ranging from 1.5 V to 3.5 V and implemented in an area of 0.011 mm(2), which is the smallest monolithic reference generator in 0.25 μm technology to the best of our knowledge. The output can vary from 20 nA to 33 nA for current reference and from 0.71 V to 1.03 V for voltage reference.
Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 08/2011; 2011:2981-4.
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ABSTRACT: In this paper, we report a neural probe which can selectively stimulate target neurons optically through Si wet etched mirror surface and record extracellular neural signals in iridium oxide tetrodes. Consequently, the proposed approach provides to improve directional problem and achieve at least 150/m gap distance between stimulation and recording sites by wet etched mirror surface in V-groove. Also, we developed light source, blue laser diode (OSRAM Blue Laser Diode_PL 450), integration through simple jig for one-touch butt-coupling. Furthermore, optical power and impedance of iridium oxide tetrodes were measured as 200 μW on 5 mW from LD and 206.5 k Ω at 1 kHz and we demonstrated insertion test of probe in 0.5% agarose-gel successfully. We have successfully transmitted a light of 450 nm to optical fiber through the integrated LD using by butt-coupling method.
Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 08/2011; 2011:2961-4.
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ABSTRACT: We report a fully-integrated low-power 3-bit programmable-gain amplifier (PGA) that can be used as the second stage amplifier to adjust the gain for multi-channel neural recording systems. The design strategy maximizes energy-efficiency using a technique by optimizing a slew rate, gain and phase margin. The PGA consumes 8.66 μW from 1-V single supply. This is an order of magnitude lower than the previous designs reported up to date. Analysis, simulation, and measurement results will be described in detail for a part of a multiplexed 16-channels neural recording system. In this implementation, while giving a full flexibility of gain control, the overhead for each channel is quite negligible: only 0.54 μW in power and less than 0.002 mm(2) in area.
Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 08/2011; 2011:2945-8.
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ABSTRACT: This paper presents a highly efficient single cell capture scheme using hydrodynamic guiding structures in a microwell array. The implemented structure has a capturing efficiency of >80%, and has a capacity to place individual cells into separated microwells, allowing for the time-lapse monitoring on single cell behavior. Feasibility was tested by injecting microbeads (15 μm in diameter) and prostate cancer PC3 cells in an 8×8 microwell array chip and >80% of the microwells were occupied by single ones. Using the chips, the number of cells required for cell assays can be dramatically reduced and this will facilitate overcoming a huddle of assays with scarce supply of cells.
Applied Physics Letters 03/2011; 98(12):123701. · 3.84 Impact Factor
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ABSTRACT: This paper reports new neural probe schemes incorporating various optical waveguides for optogenetic applications. A photodefinable polymer (SU-8) has been patterned to form optical mixer and splitter waveguides for advanced optical functions with multiple light sources and easy delivery of light to multiple shanks, respectively. Also, multiple stimulation sites have been implemented by step-wise patterning in a single waveguide. In addition to SU-8 waveguides, iridium electrodes have been integrated for recording of neural signals from optically stimulated neurons with light of specific wavelengths. Single mode optical fibers have been coupled in grooves etched in the probe body. We have successfully demonstrated transmissions of blue light, 473 nm in wavelength, through the waveguides that are integrated on the fabricated devices.
Micro Electro Mechanical Systems (MEMS), 2011 IEEE 24th International Conference on; 02/2011
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ABSTRACT: In this paper, we report real-time measurement results of various contact forces exerted on a new flexible capacitive three-axis tactile sensor array based on polydimethylsiloxane (PDMS). A unit sensor consists of two thick PDMS layers with embedded copper electrodes, a spacer layer, an insulation layer and a bump layer. There are four capacitors in a unit sensor to decompose a contact force into its normal and shear components. They are separated by a wall-type spacer to improve the mechanical response time. Four capacitors are arranged in a square form. The whole sensor is an 8 × 8 array of unit sensors and each unit sensor responds to forces in all three axes. Measurement results show that the full-scale range of detectable force is around 0–20 mN (250 kPa) for all three axes. The estimated sensitivities of a unit sensor with the current setup are 1.3, 1.2 and 1.2%/mN for the x-, y- and z-axes, respectively. A simple mechanical model has been established to calculate each axial force component from the measured capacitance value. Normal and shear force distribution images are captured from the fabricated sensor using a real-time measurement system. The mechanical response time of a unit sensor has been estimated to be less than 160 ms. The flexibility of the sensor has also been demonstrated by operating the sensor on a curved surface of 4 mm radius of curvature.
Journal of Micromechanics and Microengineering 02/2011; 21(3):035010. · 2.11 Impact Factor
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Proceedings of the 37th European Solid-State Circuits Conference, ESSCIRC 2011, Helsinki, Finland, Sept. 12-16, 2011; 01/2011
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ABSTRACT: In this paper, we report a new push-pull-type SPDT (single pole double throw) switch actuated by the combination of electromagnetic and electrostatic forces for low power and low voltage operation. The switch is initially actuated by large electromagnetic force to change its state and is held to maintain its state by applying electrostatic force to reduce static power consumption. The electromagnetic force can be easily generated at low voltage. The maximum actuation voltage is below 4.3 V and the required energy is 15.4 µJ per switching. It achieves signal isolation of −54 dB and insertion loss of −0.16 dB at 2 GHz, respectively. For 20 GHz operation, isolation and insertion loss were measured as −36 dB and −0.52 dB, respectively. The proposed SPDT switch combines two switching elements in a single structure, simplifying the overall structure and control signals and eliminating mismatches between the two switching elements. The dimension of the switch has been optimized using FEM simulation and analytical calculations. We have successfully carried out a lifetime test over more than 166 million cycles with the maximum actuation voltage below 4.3 V.
Journal of Micromechanics and Microengineering 03/2010; 20(3):035028. · 2.11 Impact Factor
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ABSTRACT: In this paper, we report a neural probe which can selectively stimulate target neurons optically from an integrated optical waveguide and also monitor extracellular neural signals in electrical recording sites. The waveguide is composed of SU-8 core and oxide cladding layer to guide a light from optical source. A U-groove has been formed at the end of the waveguide for easy alignment with an optical fiber. The coupling loss between the optical fiber and waveguide has been measured below -3.7 dB with a waveguide loss of -0.22 dB/mm. We have successfully transmitted a light of 470nm in wavelength through the integrated polymer waveguide on the neural probe.
Micro Electro Mechanical Systems (MEMS), 2010 IEEE 23rd International Conference on; 02/2010
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ABSTRACT: In this paper, we report a flexible dual-mode capacitive sensor for robot applications which has two sensing capabilities in a single platform; tactile and proximity sensing capability. The sensor consists of a mechanical structure based on PDMS (Polydimethylsiloxane) and a mesh of multiple copper electrode strips. The mesh is composed of 16 top and 16 bottom copper strips crossed each other to form a 16 times 16 capacitor array. The proposed sensor is able to switch its function from tactile sensing to proximity sensing or vice versa by reconfiguring the connection of electrodes. The tactile sensing capability has been demonstrated already and reported in our previous paper (Lee et al.,, 2006); therefore, in this paper, we will demonstrate the feasibility of the proximity sensing capability and the dual-mode operation of the proposed sensor in detail. The capacitance change caused by an approaching object has been estimated through simulation of multiple two-dimensional models as an initial study. The measured data have shown similar trends with the simulation results. We tested various materials from conducting metals to a human hand for proximity measurement. The fabricated sensor could detect a human hand at a distance up to 17 cm away from the sensor. We also have successfully demonstrated the feasibility of dual-mode operation of the proposed sensor in real-time exploiting a custom designed PCB, a data acquisition pad, and Labview software.
IEEE Sensors Journal 01/2010; · 1.52 Impact Factor
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ABSTRACT: We report an energy efficient pseudo open-loop amplifier with programmable band-pass filter developed for neural interface systems. The proposed amplifier consumes 400 nA at 2.5 V power supply. The measured thermal noise level is 85 nV/radic(Hz) and input-referred noise is 1.69 muV<sub>rms</sub> from 0.3 Hz to 1 kHz. The amplifier has a noise efficiency factor of 2.43, the lowest in the differential topologies reported up to date to our knowledge. By programming the switched-capacitor frequency and bias current, we could control the bandwidth of the preamplifier from 138 mHz to 2.2 kHz to meet various application requirements. The entire preamplifier including band-pass filters has been realized in a small area of 0.043 mm<sup>2</sup> using a 0.25 mum CMOS technology.
Engineering in Medicine and Biology Society, 2009. EMBC 2009. Annual International Conference of the IEEE; 10/2009
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ABSTRACT: We report an area-efficient 8 bit SAR ADC using dual capacitor array banks for brain signal interface microsystems. The proposed ADC consumes 680 nW and the total chip area is 0.035 mm<sup>2</sup>. We reduced the area and power by a factor of eight when compared with conventional approaches. If we increase the resolution, the area and power reduction factor exponentially increases in our architecture (e.g., a factor of 16 for 10 bit resolution). The measured SNDR, SFDR, THD, and ENOB are 42.82 plusmn 0.47 dB, 57.90 plusmn 2.82 dB, -53.58 plusmn 2.15 dB, and 6.65 plusmn 0.07 bits, respectively.
Engineering in Medicine and Biology Society, 2009. EMBC 2009. Annual International Conference of the IEEE; 10/2009
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ABSTRACT: We report our preliminary work to explore a new method of signal transmission for bio-implantable microsystems. Intra-brain communication or IBCOM is a wireless signal transmission method that uses the brain itself as a conductive medium to transmit the data and commands between neural implants and data processing systems outside the brain. Two miniaturized IBCOM (mu-IBCOM) CMOS chips were designed and fabricated for an in vivo test bed to transmit two prerecorded neural signals at different binary frequency shift keying (BFSK) carrier frequencies to validate the feasibility of IBCOM concept. The chips were packaged for full implantation in a rat brain except for external power delivery. The original neural signal waveforms were successfully recovered after being transmitted between two platinum electrodes separated by 15 mm with transmission power less than 650 pJ/bit for the CMOS implementation.
Engineering in Medicine and Biology Society, 2009. EMBC 2009. Annual International Conference of the IEEE; 10/2009
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ABSTRACT: This chapter introduces the demonstration of specific antibody detection by using a microbead-based assay with quantum dot (QD) fluorescence on a polydimethylsiloxane (PDMS) microfluidic chip. The microfluidic chip is designed to isolate a single microbead where the binding reaction of antibodies occurs on the surface. The microfluidic chip is fabricated on a glass substrate using a transparent silicone elastomer, PDMS, for easy access of monitoring and flexible gate operations to capture the single microbead. For antibody detection, a sequence of functionalized assays has been performed in the fabricated chip, including the capturing of microbeads, antibody injection into a microchamber, quantum dot injection, and fluorescence detection. Various concentrations of human IgG antibodies have been introduced to bind to a single microbead captured and isolated inside a designated microchamber in a small volume of 75 pL. Fluorescence detection is monitored using a CCD camera after the second binding with the QDs conjugated with anti-human IgG. In this experiment, a human IgG antibody concentration below 0.1 microg/mL has been successfully detected.
Methods in molecular biology (Clifton, N.J.) 02/2009; 544:53-67.
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ABSTRACT: In this paper, a new three-axis electromagnetically actuated micromirror structure has been proposed and fabricated. It is electromagnetically actuated at low voltage using an external magnetic field. The main purpose of this work was to obtain a three-axis actuated micromirror in a mechanically robust structure with large static angular and vertical displacement at low actuation voltage for fine alignment among optical components in an active alignment module as well as conventional optical systems. The mirror plate and torsion bars are made of bulk silicon using a SOI wafer, and the actuation coils are made of electroplated Au. The maximum static deflection angles were measured as ±4.2 • for x-axis actuation and ±9.2 • for y-axis actuation, respectively. The maximum static vertical displacement was measured as ±42 μm for z-axis actuation. The actuation voltages were below 3 V for all actuation. The simulated resonant frequencies are several kHz, and these imply that the fabricated micromirror can be operated in sub-millisecond order. The measured radius of curvature (ROC) of the fabricated micromirror is 7.72 cm, and the surface roughness of the reflector is below 1.29 nm which ensure high optical performance such as high directionality and reflectivity. The fabricated micromirror has demonstrated large actuated displacement at low actuation voltage, and it enables us to compensate a larger misalignment value when it is used in an active alignment module. The robust torsion bar and lifting bar structure formed by bulk silicon allowed the proposed micromirror to have greater operating stability. The additional degree of freedom with z-axis actuation can decrease the difficulty in the assembly of optical components and increase the coupling efficiency between optical components.
J. Micromech. Microeng. 01/2009; 19.
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ABSTRACT: We report an energy efficient pseudo open-loop amplifier with programmable band-pass filter developed for neural interface systems. The proposed amplifier consumes 400nA at 2.5V power supply. The measured thermal noise level is 85nV/ radicalHz and input-referred noise is 1.69microV(rms) from 0.3Hz to 1 kHz. The amplifier has a noise efficiency factor of 2.43, the lowest in the differential topologies reported up to date to our knowledge. By programming the switched-capacitor frequency and bias current, we could control the bandwidth of the preamplifier from 138 mHz to 2.2 kHz to meet various application requirements. The entire preamplifier including band-pass filters has been realized in a small area of 0.043mm(2) using a 0.25microm CMOS technology.
Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 01/2009; 2009:1631-4.
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ABSTRACT: We report our preliminary work to explore a new method of signal transmission for bio-implantable microsystems. Intra-brain communication or IBCOM is a wireless signal transmission method that uses the brain itself as a conductive medium to transmit the data and commands between neural implants and data processing systems outside the brain. Two miniaturized IBCOM (micro-IBCOM) CMOS chips were designed and fabricated for an in vivo test bed to transmit two prerecorded neural signals at different binary frequency shift keying (BFSK) carrier frequencies to validate the feasibility of IBCOM concept. The chips were packaged for full implantation in a rat brain except for external power delivery. The original neural signal waveforms were successfully recovered after being transmitted between two platinum electrodes separated by 15 mm with transmission power less than 650 pJ/bit for the CMOS implementation.
Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 01/2009; 2009:2054-7.
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ABSTRACT: We report an area-efficient 8bit SAR ADC using dual capacitor array banks for brain signal interface microsystems. The proposed ADC consumes 680nW and the total chip area is 0.035 mm(2). We reduced the area and power by a factor of eight when compared with conventional approaches. If we increase the resolution, the area and power reduction factor exponentially increases in our architecture (e.g., a factor of 16 for 10 bit resolution). The measured SNDR, SFDR, THD, and ENOB are 42.82 +/- 0.47 dB, 57.90 +/- 2.82dB, -53.58 +/- 2.15 dB, and 6.65 +/- 0.07 bits, respectively.
Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 01/2009; 2009:1647-50.
