A flexible tactile sensing module with NiCr strain gauges as sensing elements was fabricated by polymer MEMS
technology using polyimide materials where the one was the photo-definable polyimide precursor and the other was nonphoto-
definable. The unit sensor cell size of 32×32 tactile sensor array was 1mm × 1mm cell and its overall size was
5.5cm × 6.5cm. Especially, both the tactile sensor arrays and the pluggable terminals as flexible flat cable were
fabricated on the same polymer substrate easily to be connected the sensor array with a PCB board. The fabricated tactile
sensing module was measured continuously in the normal force range of 0~1N with tactile sensor evaluation system. The
value of resistance was relatively linear with normal force in the overall range of 0~1N. However, the variation of
resistance was decreased by more than 0.6N. The variation rate of resistance was 2.0%/N in the range of 0~0.6N and
1.5%/N in the range of 0.6~1N. Image display was identified corresponding by distribution of applied force. The
flexibility of the sensing module was adequate to be placed on any curved surface as a cylinder.
This paper presents the application of polypyrrole(PPy) as a medium material for the release and the detection of a neurotransmitter, i.e. epinephrine, using its electrically stimulated ion exchange property. Neuron signals are transmitted in a synapse, which is composed of releasing and detecting parts of neurotransmitters. PPy was electrochemically polymerized with NaDBS as dopants on Au electrode and then was incorporated with epinephrine by cation exchange process. The incorporated epinephrine was released by applying a controlled voltage and the released amount of epinephrine was determined using an ultraviolet (UV) spectrometry. Experimental results of the releasing part show that the released amount of epinephrine depended not only on the thickness and the size of PPy film but also on the releasing time. Spontaneously diffused epinephrine amount was measured to be only 18% of the voltage driven release amount. The absorbance change of epinephrine due to the applied potential during releasing process is negligible compared with that of the released epinephrine. Overoxidized PPy(OxPPy) for the detecting part shows a good cation permselectivity for the detection of epinephrine and the current is also higher than that at the Au electrode in the same concentration of the epinephrine. The current level is different with dopants with which the OxPPy film is polymerized and the sensitivity of the OxPPy electrode depends on the thickness of PPy film.
The morphological characteristics such as surface area, thickness, and roughness of the Polypyrrole (PPy) on metal electrodes of electrochemical sensors affect sensitivity and selectivity of electrochemical sensors because the surface morphology of PPy affects reduction and oxidation of the electrodes. The PPy morphology was investigated by changing several polymerization parameters such as polymerization time, electrolytes, and metal electrodes. Indium tin oxide (ITO) or Au was used as a seed metal electrode on which PPy was electropolymerized. The electropolymerization was performed in an electrolyte, either sodium dodecyl sulfate (NaDS) or sodium dodecyl benzene sulfonate (NaDBS). A homogeneous PPy morphology was obtained on ITO electrode when NaDBS solution was used as an electrolyte, but when NaDS solution was used for polymerizing on ITO electrode, the electropolymerized PPy showed uniform surface morphology and film thickness up to 1 min polymerization time while further polymerization resulted in non-uniform networks like a spider web. This increases the detection surface area with identical metal electrodes of electrochemical sensors. When Au was used, neither NaDBS nor NaDS solution resulted in any morphology change of the PPy film regardless of the polymerization time. The effect of the PPy morphology on the electrochemical sensors will also be presented.
This paper describes the fabrication and characteristics of an ionic polymer-metal composite (IPMC) membrane-shaped micro-actuator and its application to the fabrication of a micro-pump. After fabricating two 8mm×8mm IPMC membrane-shaped actuators using a Nafion film, their displacements were measured. The fabricated IPMC membrane-shaped micro-actuators showed displacement of 14~27μ at the applied voltage ranging from 4VP-P to 10VP-P at 0.5Hz. Displacement of the IPMC actuator fabricated with a commercially available Nafion is large enough to make the IPMC actuator a membrane-shaped micro-actuator for fabricating an IPMC micro-pump. IPMC micro-pump was fabricated by assembling IPMC membrane-shaped micro-actuator and PDMS(polydimethylsiloxane) micro-channel together. PDMS micro-channel was designed to have nozzle/diffuser structures which make the fluids flow from inlet to outlet when the IPMC membrane-shaped micro-actuator is deflected up and down by the applied voltages. The measured flow rate of the fabricated IPMC micro-pump was about 9.9μℓ/min at 0.5Hz when the input voltage and duty ratio were 8V P-P and 50%, respectively. The test results illustrate that the fabricated IPMC micro-pump is suitable for pumping fluid through micro-channel on a PDMS substrate. Mechanical performances of beam-shaped and bridge-shaped conductive polymer actuator in aqueous solution and in solid electrolyte have been measured and analyzed. The optimum thickness of polypyrrole for the best bending performance is about 17-19 μm which has been polymerized at the current density of 5.4 μA/mm2 for 120 minutes. For the application of conductive polymer actuator to a micropump, silicon bulk micromachining process has been combined.
IPMC (Ionic Polymer Metal Composite) is a promising candidate actuator for bio-related applications mainly due to its biocompatibility, soft properties and operation in wet condition. The widely used and commercialized ion-exchange polymer film has limitation in thicknesses, but more various film thicknesses are required for extensive applications. Especially for the enhanced force as an actuator, acquisition of thick film is essential. Various ion-exchange polymer films with thickness of 0.4-1.2 mm have been prepared by casting of liquid ion-exchange polymer. As well, IPMC
actuators using cast ion-exchange polymer films have been fabricated and the basic mechanical characteristics such as stiffness, displacement and force were measured and analyzed. These results can be used for the optimized design of actuators for different applications.
We have developed the wireless tadpole robot that has simple geometry, driven by low voltage and the undulatory fin-motion using IPMC(Ionic Polymer Metal Composite) actuator. Behavior of TadRob is tested under various frequencies(1~8Hz) to find the correlation between actuator frequency and velocity of the robot. In addition, the robot velocity according to undulation motion and oscillation motion of the fin is compared to find the proper fin-motion to increase the efficiency of the robot. Also, steering capability is tested under variation of duty ratio. Based on experimental results, we can confirm that the velocity of TadRob can be controlled by changing frequency of input voltage and the steering angle can be increased with increasing the duty ratio.
A quantitative analysis of drug release characteristics of polypyrrole (PPy) was performed for its application to a drug
delivery system (DDS). The incorporation of various chemical substances into the PPy and controlling its release with the externally applied voltage to the PPy are possible. A qualitative drug release characteristics of the PPy was first examined using an indicator, phenolred and then the quantitative analysis was performed using salicylate as a dopant. A drug release characteristics with time was thoroughly investigated while varying the electrode area, polymerization time, the applied voltage for drug release. Based on these quantitative results, a preliminary experiment was carried out to check the feasibility of the PPy applicable to the neuronal system. Experimental results show that a neurotransmitter was released from the PPy with the externally applied voltage and hence the PPy can be applicable in a neuronal system.
Among many kinds of polymer materials, electronic conductive material, that is polypyrrole, shows potential possibility for bio-relate actuator materials. However, it may be an impediment for practical use in polypyrrole actuator that polypyrrole usually requires electrolyte solution for actuation. Our first research theme is focused on this problem solving. We have investigated many kinds of solid polymer electrolyes for the substitution of electrolyte solution. Our goals are to find the stable solid electrolyte in the air, to establish the reliable fabrication process of it and to apply it for micropump application. Besides actuators, the reduction and oxidation property of polypyrrole can be exploited for active drug delivery systems by the control of structural deformation of it. We have investigated this kind of new and bio-related possibility of polypyrrole. Shape memory alloy has another possibility in the biomedical field. Due to its inherent excellent advantages as actuator materials, it can be used for micro active intravascular catheter. We have developed thin tube type bending actuator using shape memory alloy and characterized its performance by in-vivo test.
A 3D Feed horn shape MEMS antenna has some attractive features for array application, which can be used to improve microbolometer performance. Since MEMS technology have been faced many difficulties to fabrication of 3D feed horn shape MEMS antenna array itself. The purpose of this paper is to propose a new fabrication method to realize a 3D feed horn shape MEMS antenna array using a MRPBI(Mirror Reflected Parallel Beam Illuminator) system with an ultra-slow-rotated and inclined x-y-z stage. A high-aspect-ratio 300 micrometers sidewalls had been fabricated using SU-8 negative photo resist. It can be demonstrated to feasibility of realize 3D feed horn shape MEMS antenna array fabrication. In order to study the effect of this novel technique, the 3D feed horn shape MEMS antenna array had been simulated with HFSS(High Frequency Structure Simulator) tools and then compared with traditional 3D theoretical antenna models. As a result, it seems possible to use a 3D feed horn shape MEMS antenna at the tera hertz band to improve microbolometer performance and optical MEMS device fabrication.
In the paper, we improved the performance of the microbolometer using coupled feed horn antenna. The response time of the device was improved by reducing thermal time constant as the area of the absorption layer was reduced. We designed the shape of an absorption layer as circular structure in order to reduce the coupling loss between the antenna and the bolometer. A supporting leg for thermal isolation also has circular structure and its length increased up to 82micrometers , it reduced the thermal conductance to 4.65x 10-8[W/K]. The directivity of the designed antenna has 20.8dB. So the detectivity of the bolometer was improved to 2.37x 10-9 [cm ROOT(Hz)/W] as the noise characteristics of the bolometer was enhanced by coupling feed horn antenna. The fabrication of the bolometer are carried out by a surface micromachining method that uses a polyimide as a sacrificial layer. The absorption layer material of the bolometer is VOx and its TCR value has above 2%/K. The 3-D feed horn antenna structure can be constructed by using a PMER negative photoresist. The antenna and the bolometer can be bonded by Au-Au flip chip bonding method.
This work reports the tunneling effects of the lateral field emitters. Tunneling effect is applicable to the VMFS(vacuum magnetic field sensors). VMFS uses the fact that the trajectory of the emitted electrons are curved by the magnetic field due to Lorentz force. Poly-silicon cantilevers were used as field emitters and anode materials. Thickness of the emitter and the anode were 2μm, respectively. PSG(phospho-silicate-glass) was used as a sacrificial layer and it was etched by HF. Cantilevers were doped with POCl3(1020cm3). 2μm-thick cantilevers were fabricated onto PSG(2μm-thick). Sublimation drying method was used at releasing step to avoid stiction. Then, the device was vacuum sealed. Device was fixed to a sodalime-glass#1 with silver paste and it was wire bonded. Glass#1 has a predefined hole and a sputtered silicon-film at backside. The front-side of the device was sealed with a sodalime-glass#2 using the glass frit. After getter insertion via the hole, backside of the glass#1 was sealed electrostatically with a sodalime-glass#3 at 10-6 torr. After sealing, getter was activated. Sealing was successful to operate the tunneling device. The packaged VMFS showed reduced emission current compared with the chamber test prior to sealing. The emission currents were changed when the magnetic field was induced. A VMFS of angular anodes were tested and its sensitivity was about 3%.
A micromechanical switch, which can be used as a logic gate, is described in this paper. This switch consists of fixed input electrodes, output electrode, VCC/GND pad, and movable electrode suspended by crab-leg flexures. For mechanical switching of an electrical signal, an actuator driven by electrostatic force was used. Provided that a movable electrode is connected to VCC and a low input voltage or ground signal is applied to the fixed input electrodes and the movable electrode. The proposed micromechanical switch was fabricated by surface micromachining technology with 2 micrometers -thick poly-Si and the measured threshold voltage for ON/OFF switching was 23V.
Mechanical performances of beam-shaped and bridge-shaped conductive polymer actuator in aqueous solution and in solid electrolyte have been measured and analyzed varying polymerization conditions and operating conditions. The optimum thickness of polypyrrole for the best bending performance is about 17-19 μm which has been polymerized at the current density of 5.4 μA/mm2 for 120 minutes. For the application of conductive polymer actuator to micropump, silicon bulk micromachining process has been combined with polymer processes. By use of parylene diaphragm and anisotropic etching of silicon, the micropump structure composed of polypyrrole and solid polymer electrolyte has been fabricated successfully.
In this paper, a new method for actuating micro-mirrors, which utilizes bending of the micro-mirror plate, was proposed in order to increase the rotational angle without increasing the sacrificial layer thickness. The analytical model of the proposed actuating method was established and, based on the analytical model, the expected micro-mirror operation is presented. In order to confirm the expected operation surface-micromachined polysilicon micro-mirror operation is presented. In order to confirm the expected operation surface micromachined polysilicon micro-mirror was fabricated and tested. The bending of the micro-mirror plate, however, was not observed in the experiment with the fabricated micro-mirror. There are two possible reasons for this. One is the driving force reduction due to the decreasing of the voltage difference between the micro- mirror plate and underlying electrode caused by electrical conducting between the two. The other is the non-optimized design in the mechanical structure which caused the bending of the supporting beam before the plate starts to bend.
In conventional IR-sensors, there are problems of needing cooler and sensing wavelength limitation. These problems can be achieved by using un-cooling thermal IR senors. However, they raise the problems of the attack of pyroelectric thin film layer during the etching of sacrificial layer as well as the thermal isolation of the IR detection layer. In order to fabricate uncooled IR-sensor using pyroelectric film, multilayer should be prepared pyroelectric thin film and thermally isolating membrane structure of square-shaped microstructures. We used the direct bonding technique to avoid the thermal loss by silicon substrate and the attack of pyroelectric thin film by etchant of the sacrificial layer. Metallic Pt layer used as a top and a bottom electrodes were deposited by E-beam sputtering method, while pyroelectric thin films were prepared Sol-Gel techniques. Because the pyroelectric thin film with c-axial orientation raised thermal polarization without the polling, the more integrated capability could be achieved. We investigated the characterized of the pyroelectric thin films: P-E loop, dielectric constant, XRD etc.
This paper presents a new accelerometer which detects applied acceleration by measuring the variation of the drain current of field effect transistors (FETs). This proposed accelerometer consists of a polysilicon plate, supporting beams and source/drains of n-channel metal insulator semiconductor FETs. The polysilicon plate used as the proof mass is suspended by four flexures and separated from the substrate. The comb finger structures at the polysilicon plate edge are used as gates of FETs. In the FET of the proposed accelerometer, gate oxide of a typical MOSFET is replaced with air gap between floating gate and substrate. As an acceleration perpendicular to the substrate is applied to the proposed accelerometer, the proof mass would have a displacement proportional tot he acceleration, and the gap between proof mass and substrate would vary. This will change the drain current of the FET because the drain current of a FET is inversely proportional to the gap between a gate and a substrate.
In this paper, the design and the fabrication of a two-axes polysilicon yaw rate sensor with four vibrating masses are presented. To confirm the first mode of the designed yaw rate sensor, ANSYS simulation was performed and the resonant frequency of 28.263kHz was obtained. Due to process variations, the fabricated structure may have different resonant frequencies for reference and detection vibrations. Therefore, a simple frequency tuning structure was utilized for frequency matching. To drive the designed structure at optimum condition, Q factor was chosen to be 1000 and the driving voltage was set to 26V for one set of masses and 35V for the other set of masses. With the selected driving condition, the reference vibration amplitude would result in about 10(Mu) m for all masses. Input angular rate of 90deg/sec would vibrate big masses and small masses with the amplitude of 0.17micrometers , respectively. In the fabrication of the designed yaw rate sensor, 6micrometers thick LPCVD polysilicon was used as structural layer over phosphosilica glass sacrificial layer. Polysilicon structural layer was doped with phosphorous diffused from PSG. The patterned structure was released by sublimation drying method using p- dichlorobenzene. The total area of the fabricated yaw rate sensor is about 1.9 X 1.4 mm2.
This work reports a direct bonding method between silicon wafers using an interlayer. Thermal oxide, sputtered silicon nitride, molybdenum film and electron-beam evaporated silicon oxide were used as an interlayer. Silicon wafers were hydrophilized by one of the host nitric acid, the sulfuric acid based solution and the ammonium hydroxide based solution, mated at class 100 hemisphere and heat treated. After hydrophilization of silicon wafers, the changes of the surface roughness' were studied by the atomic force microscopy and the voids and the non-bonded areas were inspected by the infra-red transmission microscope. The bonding interfaces of the bonded pairs were inspected by a high resolution scanning electron microscope. Surface energies and tensile strengths of the bonded pairs were also tested by the crack propagation method and the push-pull meter, respectively. Surface energy of the Si-Si wafer pair annealed at 150 degree(s)C for 48 hours was about 7200 [erg/cm2] and its tensile strength was more than 18 MPa. This tensile strength is comparable with the bulk strength of the used silicon wafer.
Short-period GaAs quantum wire (QWR) array was grown by metalorganic chemical vapor deposition on submicron gratings. And a new lithography technique to fabricate submicron current-blocking layer on the short-period QWR array without any external masks was developed. The methods include the followings. The photoresist was coated on the nonplanar top of the laser diode structure. The photoresist stripes were designed to remain over each QWR with a flood exposure and a develop technique. The GaAs contact layers on the parts of the (111)A and all the (100) top quantum wells were removed by employing the photoresist remaining on the top valley as masks. The submicron current-blocking layer was produced all over the regions except QWR's, by sputtering SiO2 film followed by lift-off and metal evaporation. It must help a majority of current pass into QWR active region.
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