... Avishek R Aiyar1, Chao Song2, Seong-Hyok Kim2 and Mark G Allen1,2 ... 2009) pp 1525 [8] Wang... more ... Avishek R Aiyar1, Chao Song2, Seong-Hyok Kim2 and Mark G Allen1,2 ... 2009) pp 1525 [8] Wang YH, Lee CY and Chiang CM 2007 A MEMS-based air flow sensor with a ... 39 49379 [16] Song C, Aiyar AR, Kim SH and Allen MG 2009 Exploitation of aeroelastic effects for drift ...
This paper presents a polymer hollow microneedle array for transdermal drug delivery that is fabr... more This paper presents a polymer hollow microneedle array for transdermal drug delivery that is fabricated using UV photolithography and a single-step micromolding technique. This fabrication process patterns a 6×6 array of 1mm tall high-aspect-ratio hollow microneedles with sharp beveled tips and 150μm diameter side-opened lumens. The geometry of the beveled tip and the position of the lumen are defined simultaneously by a two-dimensional lithography mask pattern and the topography of the micromold. This three-dimensional geometry improves insertion performance and potentially the drug delivery efficiency without additional fabrication processes. These hypodermic-needle-like microneedles have been successfully constructed, packaged, and tested for fluidic functionality and skin penetrability.
2006 Solid-State, Actuators, and Microsystems Workshop Technical Digest, 2006
This paper reports a simple lateral lamination scheme for the fabrication of multilayer piezoelec... more This paper reports a simple lateral lamination scheme for the fabrication of multilayer piezoelectric actuators. The fabrication scheme consists of dicing of a high-d 33 piezoelectric coefficient lead zirconate titanate (PZT) material, photolithographic highaspect-ratio SU-8 definition of electrical isolation, and micromolding of conductive polymer electrodes. Backside and inclined UV exposure has been exploited to secure the 1mm-thick SU-8 pillar definition of internal electrodes and to prevent the formation of a tapered SU-8 pillar shape that allows electrical short paths. An electrically conductive polymer composite (ECPC, silver-PMMA: 40 vol% Ag) has been utilized for making moldable electrodes. In fabrication and actuation, it is advantageous to have the isolation structures and the electrodes to be both made with polymeric materials so that they have similar thermal and mechanical properties. An 8-layer device is successfully fabricated and tested. A displacement of 0.63 micron is achieved at 100V driving voltage, which agrees well with finite element simulation results.
Abstract: This paper presents two types of electromagnetic power generators exploiting direct con... more Abstract: This paper presents two types of electromagnetic power generators exploiting direct conversion of airflow into mechanical vibration: 1) a windbelt-based vibratory linear micro-generator targeting strong airflows, and 2) a Helmholtz resonator based generator capable of scavenging energy from weaker airflows, i.e. environmental airflows. Both devices consist of two tightly coupled parts: a mechanical resonator, which produces high-frequency mechanical oscillation from quasi-constant airflow; and a permanent magnet/coil system, which generates electrical power from the resonator’s motion. The proposed micro-generators obviate the typically required matching of the resonant frequencies of the scavenger and the ambient energy sources it taps. This enables a device that is simpler, smaller, and higher-frequency than previously reported resonant power generator. The windbelt-based micro-generator demonstrated a peak-to-peak output voltage of 81mV at 0.53kHz, from an input pressur...
An electrostatic scanning micromirror with diaphragm mirror plate and diamond-shaped reinforcemen... more An electrostatic scanning micromirror with diaphragm mirror plate and diamond-shaped reinforcement frame
A three-dimensional (3-D) metal transfer micromolding (MTM) fabrication process for low-cost, man... more A three-dimensional (3-D) metal transfer micromolding (MTM) fabrication process for low-cost, manufacturable, high-aspect-ratio MEMS structures with a patterned metal layer for electrical and biological functionalities is presented in this paper. The mechanism of MTM lies in the differences in adhesion strengths between mold-metal and replica-metal interfaces. This is an extension of a non-covalent 2-D nanotransfer printing (nTP) process and enables a simultaneous replication of high-aspect-ratio 3-D structures from a mold in a single polymer molding process. The conductive layer is patterned at this same step, enabling the resulting structure to have a patterned electrically/biologically functional 3-D metallic layer defined on the high-aspect-ratio polymer structure. This metallic layer on the polymer device has been utilized as a bio-compatible site for cell culturing, an electrode for spontaneous recording from cells and for RF MEMS functionalities. Thus combining the virtues of...
The comb actuator deformed by microloading effect in DRIE process generally has `L shape comb ele... more The comb actuator deformed by microloading effect in DRIE process generally has `L shape comb electrodes. Therefore, the actuator shows nonlinear differential driving characteristics. A simple modeling is suggested and simulated to explain the driving characteristics. For modeling convenience, the damaged comb electrode is assumed to be a simple `L shape. According to the modeling, the resonant frequency is estimated to increase as the bias voltage increases. The static displacement curve shows `S shape.
L'invention concerne un dispositif electronique et un procede de commande associe. Selon un m... more L'invention concerne un dispositif electronique et un procede de commande associe. Selon un mode de realisation de l'invention, un dispositif electronique peut comprendre : une partie de corps dont une surface arriere vient en contact avec une partie du corps d'un utilisateur ; une partie de bande qui s'etend sur un cote ou les deux cotes de la partie de corps et dont une surface arriere vient en contact avec une partie du corps d'un utilisateur ; une electrode disposee sur la surface arriere de la partie de corps ou la partie de bande et comportant une zone conductrice et une zone non conductrice ; et une unite de commande qui est montee a l'interieur de la partie de corps ou de la partie de bande et qui commande une tension appliquee a l'electrode conformement au signal biometrique d'un utilisateur obtenu par le biais de l'electrode.
Recognition of human gestures plays an important role in a number of human-interactive applicatio... more Recognition of human gestures plays an important role in a number of human-interactive applications, such as mobile phones, health monitoring systems, and human-assistive robots. Electromyography (EMG) is one of the most common and intuitive methods used for detecting gestures based on muscle activities. The EMG, however, is in general, too sensitive to environmental disturbances, such as electrical noise, electromagnetic signals, humidity, and so on. In this paper, a new method for recognizing the muscular activities is proposed based on air-pressure sensors and air-bladders. The muscular activity is detected by measuring the change of the air pressure in an air-bladder contacting the interested muscle(s). Since the change of the air pressure can be more robustly measured compared with the change of electric signals appeared on the skin, the proposed sensing method is useful for mobile devices due to its great signal-to-noise ratio (SNR) and fast response time. The principle and applications of the proposed sensing method are introduced in this paper. The performance of the proposed method is evaluated in terms of linearity, repeatability, wear-comfort, etc., and is also verified by comparing it with an EMG signal and a motion sensor.
This paper reports the fabrication and performance of an elastic electret based on polydimethylsi... more This paper reports the fabrication and performance of an elastic electret based on polydimethylsiloxane (PDMS)/carbon-nanotube (CNT) composites. The composite formulation concentrates CNTs near the surface of the PDMS and thereby combines the excellent electrical properties and room- temperature micropatternability of the CNT with the elasticity of PDMS. The material was corona-charged and the charge storage behavior was characterized using surface potential measurements. Substantial improvements in charge storage capacity and stability were observed compared to either pure PDMS or CNTs on the surface of PDMS at room temperature over a 280 hour measurement period.
2008 IEEE MTT-S International Microwave Symposium Digest, 2008
This paper presents an RF airflow sensor based on an evanescent-mode cavity resonator. The freque... more This paper presents an RF airflow sensor based on an evanescent-mode cavity resonator. The frequency loading is achieved by a capacitive post in the center of a cylinder cavity. As a sensing mechanism, an elastic membrane with a sensing beam is utilized to generate a strain on the top of the cavity. The airflow deflects the sensing beam, changing the parasitic capacitance of the cavity and hence, the resonant frequency of the resonator. The cavity resonator is fabricated by micro-molding of thermal-plastic polymers enabling a low cost batch fabrication. The coplanar waveguide (CPW) feeding structure is formed simultaneously during the molding process by using a metal transfer technique. The resonant frequency of the resonator as a function of the sensing beam deflection angle is demonstrated, and a wind tunnel test is performed to demonstrate an equivalent sensitivity of 0.36GHz/(m/s) for the air flow velocity measurement.
... 4. References [1] S. Kim, JM Park, H. Jeong, G. Park and JY. Kim, Technical Digest of ISOM 20... more ... 4. References [1] S. Kim, JM Park, H. Jeong, G. Park and JY. Kim, Technical Digest of ISOM 2002, pp.204-206, Waikoloa, 2002 [2] M. Tani, K. Inoue, M. Sekine, S. Imai, H. Awano, A. Ohta, Technical digest of ODS2001, pp61-63, 2001 Fig. 8. Flying characteristics of OFH Fig. ...
... Avishek R Aiyar1, Chao Song2, Seong-Hyok Kim2 and Mark G Allen1,2 ... 2009) pp 1525 [8] Wang... more ... Avishek R Aiyar1, Chao Song2, Seong-Hyok Kim2 and Mark G Allen1,2 ... 2009) pp 1525 [8] Wang YH, Lee CY and Chiang CM 2007 A MEMS-based air flow sensor with a ... 39 49379 [16] Song C, Aiyar AR, Kim SH and Allen MG 2009 Exploitation of aeroelastic effects for drift ...
This paper presents a vibration amplitude measurement method that greatly reduces the effects of ... more This paper presents a vibration amplitude measurement method that greatly reduces the effects of baseline resistance drift in an all-polymer piezoresistive flow sensor or microtuft. The sensor fabrication is based on flexible printed circuit board (flex-PCB) technology to enable the potential for low-cost and scalable manufacture. Drift reduction is accomplished by discriminating the flow-induced vibration ('flutter') amplitude of the microtuft-based sensor as a function of flow velocity. Flutter peak-to-peak amplitude is measured using a microcontroller-based custom readout circuit. The fabricated sensor with the readout circuitry demonstrated a drift error of 2.8 mV/h, which corresponds to a flow-referenced drift error of 0.2 m/s of wind velocity per hour. The sensor has a sensitivity of 14.5 mV/(m/s) with less than 1% nonlinearity over the velocity range of 5-16 m/s. The proposed vibration amplitude measurement method is also applied to a sensor array with a modified structure and a reduced dimension, which demonstrated a sensitivity of 13.2 mV/(m/s) with a flow-referenced drift error of 0.03 m/s of wind velocity per hour.
Inkjet-printing is a very promising technology for the development of microwave circuits and comp... more Inkjet-printing is a very promising technology for the development of microwave circuits and components. Inkjetprinting technology of conductive silver nanoparticles on an organic flexible paper substrate is introduced in this study. The paper substrate is characterised using the T-resonator method. A variety of microwave passive and active devices, as well as complete circuits inkjet-printed on paper substrates are introduced. This work includes inkjet-printed artificial magnetic conductor structures, a substrate integrated waveguide, solar-powered beacon oscillator for wireless power transfer and localisation, energy harvesting circuits and nanocarbon-based gas-sensing materials such as carbon nanotubes and graphene. This study presents an overview of recent advances of inkjet-printed electronics on paper substrate.
... Avishek R Aiyar1, Chao Song2, Seong-Hyok Kim2 and Mark G Allen1,2 ... 2009) pp 1525 [8] Wang... more ... Avishek R Aiyar1, Chao Song2, Seong-Hyok Kim2 and Mark G Allen1,2 ... 2009) pp 1525 [8] Wang YH, Lee CY and Chiang CM 2007 A MEMS-based air flow sensor with a ... 39 49379 [16] Song C, Aiyar AR, Kim SH and Allen MG 2009 Exploitation of aeroelastic effects for drift ...
This paper presents a polymer hollow microneedle array for transdermal drug delivery that is fabr... more This paper presents a polymer hollow microneedle array for transdermal drug delivery that is fabricated using UV photolithography and a single-step micromolding technique. This fabrication process patterns a 6×6 array of 1mm tall high-aspect-ratio hollow microneedles with sharp beveled tips and 150μm diameter side-opened lumens. The geometry of the beveled tip and the position of the lumen are defined simultaneously by a two-dimensional lithography mask pattern and the topography of the micromold. This three-dimensional geometry improves insertion performance and potentially the drug delivery efficiency without additional fabrication processes. These hypodermic-needle-like microneedles have been successfully constructed, packaged, and tested for fluidic functionality and skin penetrability.
2006 Solid-State, Actuators, and Microsystems Workshop Technical Digest, 2006
This paper reports a simple lateral lamination scheme for the fabrication of multilayer piezoelec... more This paper reports a simple lateral lamination scheme for the fabrication of multilayer piezoelectric actuators. The fabrication scheme consists of dicing of a high-d 33 piezoelectric coefficient lead zirconate titanate (PZT) material, photolithographic highaspect-ratio SU-8 definition of electrical isolation, and micromolding of conductive polymer electrodes. Backside and inclined UV exposure has been exploited to secure the 1mm-thick SU-8 pillar definition of internal electrodes and to prevent the formation of a tapered SU-8 pillar shape that allows electrical short paths. An electrically conductive polymer composite (ECPC, silver-PMMA: 40 vol% Ag) has been utilized for making moldable electrodes. In fabrication and actuation, it is advantageous to have the isolation structures and the electrodes to be both made with polymeric materials so that they have similar thermal and mechanical properties. An 8-layer device is successfully fabricated and tested. A displacement of 0.63 micron is achieved at 100V driving voltage, which agrees well with finite element simulation results.
Abstract: This paper presents two types of electromagnetic power generators exploiting direct con... more Abstract: This paper presents two types of electromagnetic power generators exploiting direct conversion of airflow into mechanical vibration: 1) a windbelt-based vibratory linear micro-generator targeting strong airflows, and 2) a Helmholtz resonator based generator capable of scavenging energy from weaker airflows, i.e. environmental airflows. Both devices consist of two tightly coupled parts: a mechanical resonator, which produces high-frequency mechanical oscillation from quasi-constant airflow; and a permanent magnet/coil system, which generates electrical power from the resonator’s motion. The proposed micro-generators obviate the typically required matching of the resonant frequencies of the scavenger and the ambient energy sources it taps. This enables a device that is simpler, smaller, and higher-frequency than previously reported resonant power generator. The windbelt-based micro-generator demonstrated a peak-to-peak output voltage of 81mV at 0.53kHz, from an input pressur...
An electrostatic scanning micromirror with diaphragm mirror plate and diamond-shaped reinforcemen... more An electrostatic scanning micromirror with diaphragm mirror plate and diamond-shaped reinforcement frame
A three-dimensional (3-D) metal transfer micromolding (MTM) fabrication process for low-cost, man... more A three-dimensional (3-D) metal transfer micromolding (MTM) fabrication process for low-cost, manufacturable, high-aspect-ratio MEMS structures with a patterned metal layer for electrical and biological functionalities is presented in this paper. The mechanism of MTM lies in the differences in adhesion strengths between mold-metal and replica-metal interfaces. This is an extension of a non-covalent 2-D nanotransfer printing (nTP) process and enables a simultaneous replication of high-aspect-ratio 3-D structures from a mold in a single polymer molding process. The conductive layer is patterned at this same step, enabling the resulting structure to have a patterned electrically/biologically functional 3-D metallic layer defined on the high-aspect-ratio polymer structure. This metallic layer on the polymer device has been utilized as a bio-compatible site for cell culturing, an electrode for spontaneous recording from cells and for RF MEMS functionalities. Thus combining the virtues of...
The comb actuator deformed by microloading effect in DRIE process generally has `L shape comb ele... more The comb actuator deformed by microloading effect in DRIE process generally has `L shape comb electrodes. Therefore, the actuator shows nonlinear differential driving characteristics. A simple modeling is suggested and simulated to explain the driving characteristics. For modeling convenience, the damaged comb electrode is assumed to be a simple `L shape. According to the modeling, the resonant frequency is estimated to increase as the bias voltage increases. The static displacement curve shows `S shape.
L'invention concerne un dispositif electronique et un procede de commande associe. Selon un m... more L'invention concerne un dispositif electronique et un procede de commande associe. Selon un mode de realisation de l'invention, un dispositif electronique peut comprendre : une partie de corps dont une surface arriere vient en contact avec une partie du corps d'un utilisateur ; une partie de bande qui s'etend sur un cote ou les deux cotes de la partie de corps et dont une surface arriere vient en contact avec une partie du corps d'un utilisateur ; une electrode disposee sur la surface arriere de la partie de corps ou la partie de bande et comportant une zone conductrice et une zone non conductrice ; et une unite de commande qui est montee a l'interieur de la partie de corps ou de la partie de bande et qui commande une tension appliquee a l'electrode conformement au signal biometrique d'un utilisateur obtenu par le biais de l'electrode.
Recognition of human gestures plays an important role in a number of human-interactive applicatio... more Recognition of human gestures plays an important role in a number of human-interactive applications, such as mobile phones, health monitoring systems, and human-assistive robots. Electromyography (EMG) is one of the most common and intuitive methods used for detecting gestures based on muscle activities. The EMG, however, is in general, too sensitive to environmental disturbances, such as electrical noise, electromagnetic signals, humidity, and so on. In this paper, a new method for recognizing the muscular activities is proposed based on air-pressure sensors and air-bladders. The muscular activity is detected by measuring the change of the air pressure in an air-bladder contacting the interested muscle(s). Since the change of the air pressure can be more robustly measured compared with the change of electric signals appeared on the skin, the proposed sensing method is useful for mobile devices due to its great signal-to-noise ratio (SNR) and fast response time. The principle and applications of the proposed sensing method are introduced in this paper. The performance of the proposed method is evaluated in terms of linearity, repeatability, wear-comfort, etc., and is also verified by comparing it with an EMG signal and a motion sensor.
This paper reports the fabrication and performance of an elastic electret based on polydimethylsi... more This paper reports the fabrication and performance of an elastic electret based on polydimethylsiloxane (PDMS)/carbon-nanotube (CNT) composites. The composite formulation concentrates CNTs near the surface of the PDMS and thereby combines the excellent electrical properties and room- temperature micropatternability of the CNT with the elasticity of PDMS. The material was corona-charged and the charge storage behavior was characterized using surface potential measurements. Substantial improvements in charge storage capacity and stability were observed compared to either pure PDMS or CNTs on the surface of PDMS at room temperature over a 280 hour measurement period.
2008 IEEE MTT-S International Microwave Symposium Digest, 2008
This paper presents an RF airflow sensor based on an evanescent-mode cavity resonator. The freque... more This paper presents an RF airflow sensor based on an evanescent-mode cavity resonator. The frequency loading is achieved by a capacitive post in the center of a cylinder cavity. As a sensing mechanism, an elastic membrane with a sensing beam is utilized to generate a strain on the top of the cavity. The airflow deflects the sensing beam, changing the parasitic capacitance of the cavity and hence, the resonant frequency of the resonator. The cavity resonator is fabricated by micro-molding of thermal-plastic polymers enabling a low cost batch fabrication. The coplanar waveguide (CPW) feeding structure is formed simultaneously during the molding process by using a metal transfer technique. The resonant frequency of the resonator as a function of the sensing beam deflection angle is demonstrated, and a wind tunnel test is performed to demonstrate an equivalent sensitivity of 0.36GHz/(m/s) for the air flow velocity measurement.
... 4. References [1] S. Kim, JM Park, H. Jeong, G. Park and JY. Kim, Technical Digest of ISOM 20... more ... 4. References [1] S. Kim, JM Park, H. Jeong, G. Park and JY. Kim, Technical Digest of ISOM 2002, pp.204-206, Waikoloa, 2002 [2] M. Tani, K. Inoue, M. Sekine, S. Imai, H. Awano, A. Ohta, Technical digest of ODS2001, pp61-63, 2001 Fig. 8. Flying characteristics of OFH Fig. ...
... Avishek R Aiyar1, Chao Song2, Seong-Hyok Kim2 and Mark G Allen1,2 ... 2009) pp 1525 [8] Wang... more ... Avishek R Aiyar1, Chao Song2, Seong-Hyok Kim2 and Mark G Allen1,2 ... 2009) pp 1525 [8] Wang YH, Lee CY and Chiang CM 2007 A MEMS-based air flow sensor with a ... 39 49379 [16] Song C, Aiyar AR, Kim SH and Allen MG 2009 Exploitation of aeroelastic effects for drift ...
This paper presents a vibration amplitude measurement method that greatly reduces the effects of ... more This paper presents a vibration amplitude measurement method that greatly reduces the effects of baseline resistance drift in an all-polymer piezoresistive flow sensor or microtuft. The sensor fabrication is based on flexible printed circuit board (flex-PCB) technology to enable the potential for low-cost and scalable manufacture. Drift reduction is accomplished by discriminating the flow-induced vibration ('flutter') amplitude of the microtuft-based sensor as a function of flow velocity. Flutter peak-to-peak amplitude is measured using a microcontroller-based custom readout circuit. The fabricated sensor with the readout circuitry demonstrated a drift error of 2.8 mV/h, which corresponds to a flow-referenced drift error of 0.2 m/s of wind velocity per hour. The sensor has a sensitivity of 14.5 mV/(m/s) with less than 1% nonlinearity over the velocity range of 5-16 m/s. The proposed vibration amplitude measurement method is also applied to a sensor array with a modified structure and a reduced dimension, which demonstrated a sensitivity of 13.2 mV/(m/s) with a flow-referenced drift error of 0.03 m/s of wind velocity per hour.
Inkjet-printing is a very promising technology for the development of microwave circuits and comp... more Inkjet-printing is a very promising technology for the development of microwave circuits and components. Inkjetprinting technology of conductive silver nanoparticles on an organic flexible paper substrate is introduced in this study. The paper substrate is characterised using the T-resonator method. A variety of microwave passive and active devices, as well as complete circuits inkjet-printed on paper substrates are introduced. This work includes inkjet-printed artificial magnetic conductor structures, a substrate integrated waveguide, solar-powered beacon oscillator for wireless power transfer and localisation, energy harvesting circuits and nanocarbon-based gas-sensing materials such as carbon nanotubes and graphene. This study presents an overview of recent advances of inkjet-printed electronics on paper substrate.
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