Showing papers in "Sensors and Actuators A-physical in 2005"
TL;DR: In this paper, a cantilever device is designed to have a flat structure with a proof mass added to the end to create electrical energy via the piezoelectric effect.
Abstract: A thin film lead zirconate titanate, Pb(Zr,Ti)O 3 (PZT), MEMS power generating device is developed. It is designed to resonate at specific frequencies from an external vibrational energy source, thereby creating electrical energy via the piezoelectric effect. Our cantilever device is designed to have a flat structure with a proof mass added to the end. The Pt/Ti top electrode is patterned into an interdigitated shape on top of the sol–gel-spin coated PZT thin film in order to employ the d33 mode of the piezoelectric transducer. This d33 mode design generates 20 times higher voltage than that of the d31 mode design of the same beam dimension. The base-shaking experiments at the first resonant frequency (13.9 kHz) generate charge proportional to the tip displacement of the cantilever with a linearity coefficient of 4.14 pC/ m. A
825 citations
TL;DR: In this article, a high-resolution projection micro-stereolithography (PμSL) process by using the Digital Micromirror Device (DMD™, Texas Instruments) as a dynamic mask is presented.
Abstract: We present in this paper the development of a high-resolution projection micro-stereolithography (PμSL) process by using the Digital Micromirror Device (DMD™, Texas Instruments) as a dynamic mask. This unique technology provides a parallel fabrication of complex three-dimensional (3D) microstructures used for micro electro-mechanical systems (MEMS). Based on the understanding of underlying mechanisms, a process model has been developed with all critical parameters obtained from the experimental measurement. By coupling the experimental measurement and the process model, the photon-induced curing behavior of the resin has been quantitatively studied. The role of UV doping has been thereafter justified, as it can effectively reduce the curing depth without compromising the chemical property of the resin. The fabrication of complex 3D microstructures, such as matrix, and micro-spring array, with the smallest feature of 0.6 μm, has been demonstrated.
760 citations
TL;DR: A high-throughput continuous cell separation chip using hydrodynamic dielectrophoresis (DEP) process that demonstrates the constant cell separation performance for varying mixture flow-rates is presented.
Abstract: We present a high-throughput continuous cell separation chip using hydrodynamic dielectrophoresis (DEP) process. The continuous cell separation chip uses three planar electrodes in a separation channel, where the positive DEP cells are moved away from the central streamline while the negative DEP cells remain in the central streamline. In the experimental study, we use the mixture of viable (live) and nonviable (dead) yeast cells in order to obtain the continuous cell separation conditions. For the conditions of the electric fields frequency of 5 MHz and the medium conductivity of 5 μS/cm, the fabricated chip performs a continuous separation of the yeast cell mixture at the varying flow-rate in the range of 0.1–1 μl/min; thereby, resulting in the purity ranges of 95.9–97.3 and 64.5–74.3%, respectively, for the viable and nonviable yeast cells. The present chip demonstrates the constant cell separation performance for varying mixture flow-rates.
308 citations
TL;DR: In this paper, a pre-strained circular actuator made of a dielectric elastomer is investigated: constitutive models based on uniaxial data are verified by comparing calculation results with experimental observations.
Abstract: Dielectric elastomers are used for the realization of actuators with large deformations and belong to the group of so-called electroactive polymers (EAP). Models are required for the design and optimization of EAP actuators. Thereby the constitutive behavior of the elastomer is of crucial importance and typically uniaxial experiments are performed in order to determine the mechanical properties of these materials. In this paper a pre-strained circular actuator made of a dielectric elastomer is investigated: constitutive models based on uniaxial data are verified by comparing calculation results with experimental observations. An analytical model is derived for the instantaneous response to an activation voltage in the pre-strained circular actuator and a finite element model is used to simulate the time-dependent behavior. Hyperelastic models are used and three strain energy formulations (Yeoh, Ogden and Mooney-Rivlin) are compared in their predictive capabilities. The results of the calculations with the three strain energy forms differ significantly, although all forms were successfully fitted to the same uniaxial data set. Predictions of the actuator behavior with the Yeoh form agree to a great extent with the measurements. The results of the present work show that the circular actuator set-up represents a valid model system for the characterization and optimization of the electromechanical behavior of dielectric elastomers.
257 citations
TL;DR: In this paper, a laminate plate theory model for a stacked multimorph cantilever actuator, encompassing all possible layups, layer anisotropies, internal and external excitations, and intrinsic and extrinsic geometries, is presented.
Abstract: The design and analysis of piezoelectric actuators is rarely optimized for low mass applications. However, emerging technologies such as micro air vehicles, and microrobotics in general, demand high force, high displacement, low mass actuators. Utilization of generic piezoceramics and high performance composite materials coupled with intelligent use of geometry and novel driving techniques yields low cost, rapidly prototyped, ultra-high energy density bending actuators for use in such applications. The design is based upon a laminate plate theory model for a stacked multimorph cantilever actuator, encompassing all possible layups, layer anisotropies, internal and external excitations, and intrinsic and extrinsic geometries. Using these principles, we have fabricated 12 mg PZT bimorph actuators with greater than 2 J kg −1 energy density. This gives a performance increase of an order of magnitude or greater compared to existing commercially available piezoelectric bending actuators.
252 citations
TL;DR: In this article, a multimodal tactile sensor made of polymer materials and metal thin film sensors is presented, which can detect the hardness, thermal conductivity, temperature, and surface contour of a contact object for comprehensive evaluation of contact objects and events.
Abstract: We present the design, fabrication process, and characterization of a multimodal tactile sensor made of polymer materials and metal thin film sensors The multimodal sensor can detect the hardness, thermal conductivity, temperature, and surface contour of a contact object for comprehensive evaluation of contact objects and events Polymer materials reduce the cost and the fabrication complexity for the sensor skin, while increasing mechanical flexibility and robustness Experimental tests show the skin is able to differentiate between objects using measured properties
236 citations
TL;DR: In this paper, a novel electrostatic micromachined pump for medical applications is designed and simulated, and the proposed structure for the micropump consists of an input and an output port, three membranes, three active membrane valves, microchannels, and three electrostatic actuation systems.
Abstract: A novel electrostatic micromachined pump for medical applications is designed and simulated. The proposed structure for the micropump consists of an input and an output port, three membranes, three active membrane valves, microchannels, and three electrostatic actuation systems. Pumping mechanism of the proposed micropump is based on the peristaltic motion that has some advantages, such as high controllability and precision, over the other mechanism that makes it suitable to be used for the medical applications. Electrostatic actuation has been employed for the deflection of the membranes because of its benefits, such as the smaller size of the device in comparison with the other types, especially piezoelectric counterpart and so on. Employing active membrane valves instead of passive check valves resolves some of the problems, such as valve clogging and leakage. The designed micropump satisfies all medical drug delivery requirements, such as drug compatibility, flow rate controllability, self-priming, small chip size, and low power consumption. The flow rate of the designed micropump is 9.1 μl/min which is quite suitable for drug delivery applications, such as chemotherapy. Total size of the designed micropump is 7 mm × 4 mm × 1 mm, which is smaller than the other peristaltic counterpart micropumps. Assuming zero residual stress, low actuation voltage, and small size are the main advantages of our design. The designed micropump is simulated by the finite element method, using the ANSYS 5.7 software.
220 citations
TL;DR: In this paper, a high-performance piezoelectric cantilever-valve micropump was investigated for drug delivery and the effect of valve design on the output performance was analyzed.
Abstract: With a micropump, the release rate of drug delivery is able to be controlled easily to maintain the therapeutic efficacy. A high-performance piezoelectric cantilever-valve micropump was investigated for this purpose. The effect of valves on the output performance of the PZT micropump was analyzed at first. With taking into account the influence of liquid added mass and added damping on the natural frequency of the valves and actuator, the design method of the cantilever valve was presented. Two micropumps were designed and fabricated for comparing experiments. The micropump with cantilever valves 2.5 mm in length obtained higher output values (the maximum flow rate and backpressure is 3.5 ml/min and 27 kPa, respectively) and had two optimal frequencies (0.8 and 3 kHz). While the micropump with cantilever valves 4.5 mm in length had only one optimal frequency (0.2 kHz), at which the micropump achieved lower output values (the maximum flow rate and backpressure is 3.0 ml/min and 9 kPa, respectively). The study results suggest that the output values and optimal frequency of micropump can be improved by the design of the cantilever valves.
214 citations
TL;DR: In this paper, a silicon-based three-axial force sensor is used in a flexible smart interface for biomechanical measurements, which combines responses from four piezoresistors obtained by ion implantation in a high aspect-ratio cross-shape flexible element equipped with a 525 m high silicon mesa.
Abstract: This paper presents the design and development of a silicon-based three-axial force sensor to be used in a flexible smart interface for biomechanical measurements. Normal and shear forces are detected by combining responses from four piezoresistors obtained by ion implantation in a high aspect-ratio cross-shape flexible element equipped with a 525 m high silicon mesa. The mesa is obtained by a subtractive dry etching process of the whole handle layer of an SOI wafer. Piezoresistor size ranges between 6 and 10m in width, and between 30 and 50m in length. The sensor configuration follows a hybrid integration approach for interconnection and for future electronic circuitry system integration. The sensor ability to measure both normal and shear forces with high linearity ( ∼99%) and low hysteresis is demonstrated by means of tests performed by applying forces from 0 to 2 N. In this paper the packaging design is also presented and materials for flexible sensor array preliminary assembly are described. © 2005 Elsevier B.V. All rights reserved.
208 citations
TL;DR: In this article, the authors considered various sensor principles for the on-line monitoring of thermal aging of engine oils, which can be efficiently measured using microacoustic sensors, compared to conventional viscometers, which need to be considered in the interpretation of the measurement results.
Abstract: There is an increasing demand for the on-line condition monitoring of lubricating oils. In our recent research, we considered various sensor principles for the on-line monitoring of thermal aging of engine oils. One of the investigated parameters is the viscosity of the lubricating oil, which can be efficiently measured using microacoustic sensors. Compared to conventional viscometers, these sensors probe a different rheological domain, which needs to be considered in the interpretation of the measurement results. This specific behavior is examined by systematically investigating engine oils with and without additive packages, which were subjected to a defined artificial aging process.
196 citations
TL;DR: In this article, a mass sensing concept based on parametric resonance amplification is proposed and experimentally investigated using a non-interdigitated comb-finger driven micro-oscillator, where mass change can be detected by measuring frequency shift at the boundary of the first order Parametric resonance ‘tongue’.
Abstract: A mass sensing concept based on parametric resonance amplification is proposed and experimentally investigated using a non-interdigitated comb-finger driven micro-oscillator. Mass change can be detected by measuring frequency shift at the boundary of the first order parametric resonance ‘tongue’. Both platinum deposition using focused ion beam (FIB) and water vapor desorption and absorption are used to change the mass of a prototype sensor. Due to the sharp transition in amplitude caused by parametric resonance, the sensitivity is 1–2 order of magnitude higher than the same oscillator working at Simple Harmonic Resonance (SHR) mode in air. Picogram (10 −12 g) level mass change can be easily detected in the sensor with mass about 30 ng and resonance frequency less than 100 kHz. Damping effects and noise processes on sensor dynamics and sensing performance are also investigated and damping has no significant effect on sensor noise floor and sensitivity. Higher sensitivity is expected when the oscillator design is optimized and dimensions are scaled.
TL;DR: In this paper, the authors investigated the use of deep reactive ion etching (DRIE) and the tailoring of etch selectivity for precise fabrication and found that the non-uniformity and surface roughness characteristics are scaled by the etch selectsivity when the 3D profile is transferred into the silicon.
Abstract: Micromachining arbitrary 3D silicon structures for micro-electromechanical systems can be accomplished using gray-scale lithography along with dry anisotropic etching. In this study, we have investigated the use of deep reactive ion etching (DRIE) and the tailoring of etch selectivity for precise fabrication. Silicon loading, the introduction of an O 2 step, wafer electrode power, and wafer temperature are evaluated and determined to be effective for coarsely controlling etch selectivity in DRIE. The non-uniformity and surface roughness characteristics are evaluated and found to be scaled by the etch selectivity when the 3D profile is transferred into the silicon. A micro-compressor is demonstrated using gray-scale lithography and DRIE showing that etch selectivity can be successfully tailored for a specific application. © 2004 Elsevier B.V. All rights reserved.
TL;DR: In this paper, a method for simultaneous compensation of the hysteresis and creep of piezoelectric actuator based on an inverse control in open-loop operation is described.
Abstract: Piezoelectric actuators are frequently used nowadays in a wide variety of positioning devices. However, a major deficiency of piezoelectric actuators is that their open-loop control accuracy is seriously limited by hysteresis and creep effects. This paper describes a method for simultaneous compensation of the hysteresis and creep of piezoelectric actuator based on an inverse control in open-loop operation. The basis of the inverse control is formed by a hysteresis mathematical model and a creep model, which can describe precisely two phenomena. The method of solving inverse models of hysteresis and creep is described detailedly. Finally, a tracking control experiment of piezoelectric actuators for a desired trajectory is performed according to the proposed method and the experimental results demonstrate that the positioning precision is noticeably improved in open-loop operation compared to the conventional open-loop control without any compensation.
TL;DR: In this paper, a new compressible conducting material has been developed by coating polyurethane (PU) foam with inherently conducting polypyrrole (PPy), and the optimised conditions for preparation of the conducting foam have been investigated.
Abstract: A new compressible conducting material has been developed by coating polyurethane (PU) foam with inherently conducting polypyrrole (PPy). The optimised conditions for preparation of the conducting foam have been investigated. Evaluation of the conducting foam shows that a linear relationship exists between the conductance and the stress applied. Parameters such as sensitivity, dynamic range, repeatability of this pressure sensor are discussed. The use of this soft pressure sensor in a prototype breath monitor is also reported.
TL;DR: In this article, the Young's modulus, residual stress, and stress gradient of electroplated gold thin films using surface micromachined beam structures were measured, and the average residual stress was found to be tensile in nature.
Abstract: We have measured the Young’s modulus, residual stress, and stress gradient of electroplated gold thin films using surface micromachined beam structures. Cantilever and bridge beam structures of different lengths were fabricated using UV-LIGA surface micromachining and dry-release methods. The Young’s modulus and residual stress of the fabricated beams were determined from the resonance frequencies of electrostatically excited beams, and the stress gradient was evaluated from the self-deformation of released cantilevers. The observed Young’s modulus was smaller than the bulk Young’s modulus, and showed small changes depending on the deposition current density. The average residual stress was found to be tensile in nature, and the observed residual stresses showed no differences, regardless of the current density. However, the stress gradient increased with increasing current density. The deformation of the cantilever beam after release was dependent on the plasma ashing time used. This result implies that additional thermal effects from the post-deposition process may have an influence on the final performance of fabricated micro electro mechanical systems (MEMS) devices.
TL;DR: In this article, the SU-8 chips with enclosed microchannels and high density of fluidic inlets have been made in a three-layer process which involves SU 8 to SU 8 adhesive bonding and sacrificial etching.
Abstract: Free-standing SU-8 chips with enclosed microchannels and high density of fluidic inlets have been made in a three-layer process which involves SU-8 to SU-8 adhesive bonding and sacrificial etching. With this process we can fabricate microchannels with depths ranging from 10 to 500 μm, channel widths from 10 to 2000 μm and lengths up to 6 cm. The process is optimized with respect to SU-8 glass transition temperature. Thermal stresses and thickness non-uniformities of SU-8 are compensated by novel mask design features, the auxiliary moats. With these process innovations filling of microchannels can be prevented, non-bonded area is minimized and bonding yields are 90% for large-area microfluidic chips. We have released up to 100 mm in diameter sized microfluidic chips completely from carrier wafers. These free-standing SU-8 chips are mechanically strong and show consistent wetting and capillary filling with aqueous fluids. Fluidic inlets were made in SU-8 chips by adding one lithography step, eliminating through-wafer etching or drilling. In our process the inlet size and density is limited by lithography only.
TL;DR: In this paper, a theory for the actuation strain of a silicone dielectric elastomer actuator with a simple geometry is developed, where the stress is a function of two variables, the strain and the applied voltage.
Abstract: A theory for the actuation strain of a silicone dielectric elastomer actuator with a simple geometry is developed. The stress is a function of two variables, the strain and the applied voltage. A lamination type stress–strain function was employed, due to the nature of the electrodes. All parameters are obtained from physical measurements. Then, measurements of the blocking force are shown to correspond to what is expected from the Maxwell stress. Actuation strain measurements are performed and compared with the developed theory. The developed model has no free parameters, yet it exhibits the features of the actuation strain: the optimum load is reproduced correctly (within the chosen experiment resolution of 5 g). The discrepancy on the actuation strain between the measurement results and the model vary between 15% and 37% at the optimum, which are ascribed to inaccuracies in dimension measurements of the actuator and the inherent crudeness in the assumption that the stress and strain fields are constant throughout the actuator. We conclude that even for high strains, the actuation of dielectric elastomer actuators is well described by only considering the elasticity of the material and the Maxwell stress due to the applied electric field.
TL;DR: In this article, a solid propellant micro-thruster with Au/Ti igniter is demonstrated as an improved micropropulsion system for micro-spacecraft, which provides a high degree of flexibility, maneuverability and integration.
Abstract: A solid propellant microthruster with Au/Ti igniter is demonstrated as an improved micropropulsion system for microspacecraft. The new design provides the microthruster with a high degree of flexibility, maneuverability and integration. Single microthruster and microthruster arrays have been successfully fabricated using standard microfabrication technologies. The propellant combustion process in the micro-chamber of the microthruster has been visually observed. Initial tests employing gunpowder-based solid propellants, have produced 2.11 × 10−5 to 1.15 × 10−4 N s of total impulse and 2.68–14.65 s of specific impulse at sea level, and 3.52 × 10−5 to 2.22 × 10−4 N s of total impulse and 4.48–28.29 s of specific impulse in vacuum. The performance of the solid propellant microthruster with Au/Ti igniter is also compared with that of a solid propellant microthruster having a wire igniter.
TL;DR: In this paper, a peristaltic PDMS micropump with microheaters on the glass substrate and a microchannel connecting the chambers and the inlet/outlet port is presented.
Abstract: This paper presents fabrication and drive test of a peristaltic PDMS micropump actuated by the thermopneumatic force. The micropump consists of the three peristaltic-type actuator chambers with microheaters on the glass substrate and a microchannel connecting the chambers and the inlet/outlet port. The micropump is fabricated by the spin-coating process, the two-step curing process, the molding process using negative photoresist, etc. The diameter and the thickness of the actuator diaphragm are 2.5 mm and 30 μm, respectively. The meniscus motion in the capillary tube is observed with a video camera and the flow rate of the micropump is calculated through the frame analysis of the recorded video data. The maximum flow rate of the micropump is about 0.36 μL/s at 2 Hz for the zero hydraulic pressure difference, when the three-phase input voltage is 20 V.
TL;DR: The developed navigation system as well as the methods of error calibration and then compensation is described, especially focused on calibration of errors caused by sensors deviations from orthogonal directions and sensor triplets deviations.
Abstract: The article deals with fully digital navigation system based on AMR sensors and accelerometers. It provides information about actual azimuth, roll and pitch. The developed navigation system as well as the methods of error calibration and then compensation is described. The article is especially focused on calibration of errors caused by sensors deviations from orthogonal directions and sensor triplets deviations. The advantage and comparisons of gimbaled and non-gimbaled navigation system will be also discussed.
TL;DR: In this paper, a simple fiber optic Fabry-Perot interferometer (FPI) sensor is used to precisely monitor changes in the refractive index of gases, and the operating principle of the sensor is discussed in this paper.
Abstract: We have developed a simple fiber optic Fabry-Perot interferometer (FPI) sensor that is used to precisely monitor changes in the refractive index of gases. The operating principle of the sensor is discussed in this paper, and it was noticed that the wavelength positions of the FPI reflectance peaks change linearly with the refractive index of gases. Using this unique property of FPI sensors, it is feasible to achieve a resolution of better than 10 −5 in monitoring the changes in the refractive index of gases. The sensor has been successfully used to monitor changes in the refractive index of nitrogen gas as a function of pressure.
TL;DR: In this paper, a thermo-pneumatic in-channel microvalve applicable to integrated blood test system is presented, where polydimethylsiloxane (PDMS) is employed as the diaphragm material for a long stroke actuation in micro-valve operation and high sealing performance.
Abstract: In this paper, a thermo-pneumatic in-channel microvalve applicable to integrated blood test system is presented. Thermo-pneumatic actuator separated in drive chamber part and thermal expansion chamber part (two-chamber configuration) is newly proposed for the purpose to reduce direct heat transfer from microheater to flow channel. Polydimethylsiloxane (PDMS) is employed as the diaphragm material for a long stroke actuation in microvalve operation and high sealing performance of liquid. It is also used as adhesive layer between glass and silicon in the structure. The microvalve with the proposed structure was fabricated. Both static and dynamic flow control characteristics were evaluated with a liquid sample (DI water) and a gas sample (N 2 ), respectively. A high ON/OFF ratio of liquid sample was obtained thanks to the soft PDMS diaphragm. Liquid sealing performance in the closed state was high enough for our application (
TL;DR: In this article, the authors presented a potentially low voltage high electrostatic torque micromachined mirror capable of two-dimensional (2-D) scans (simultaneous transverse and longitudinal scans) for optical coherence tomographic imaging.
Abstract: With the inherent advantages of micromachining technologies such as small size, small mass, low cost, low power consumption and high reliability, there will be radical changes to biomedical devices and how clinical diagnoses are made. One of the most promising applications of microtechnologies is in the field of medical science. This paper presents a potentially low voltage high electrostatic torque micromachined mirror capable of two-dimensional (2-D) scans (simultaneous transverse and longitudinal scans) for optical coherence tomographic imaging. When the micro-mirror is integrated with an optical coherence tomography (OCT) system, three-dimensional (3-D) sample images can be obtained in one longitudinal scan period. 3-D images of internal-organs of fruit fly ( Drosophila melanogaster ) and its larva are acquired using the micromachined-based OCT system. The dimension of the micromachined mirror is 1000 um × 1000 um. The entire MEMS scanner is made of single-silicon crystal, to act as mechanical reinforcement counteracting the inherent stresses of the deposited thin films on the mirror. The scanning mirror is actuated electrostatically.
TL;DR: In this paper, the accuracy and resolution of direct resistive sensor-to-microcontroller interfaces using theoretical and experimental methods are analyzed. But the experimental results were similar for both microcontrollers and agreed with theoretical predictions.
Abstract: This paper analyses the accuracy and resolution of direct resistive sensor-to-microcontroller interfaces using theoretical and experimental methods. Three calibration techniques are evaluated: single-point, two-point and three-signal. This last method is a two-point calibration technique that needs a single calibration resistor. For each calibration formula, we analyse both the effects of the internal resistances of the microcontroller pins on the accuracy and the resolution, which is evaluated by the combined standard uncertainty of the calculated resistance. The experimental analysis was performed by measuring resistors in the range of Pt1000-type temperature sensors with two commercial microcontrollers (AVR AT90S2313 and PIC16F873). The experimental results were similar for both microcontrollers and agreed with theoretical predictions. For the AVR, the three-signal measurement method yielded a 0.01% relative systematic error and a 0.10 Ω resolution when averaging 10 calculated resistances.
TL;DR: In this paper, a large vertical displacement (LVD) microactuator that can generate large piston motion and bi-directional scanning at low driving voltage is presented, which can also be used to perform bidirectional rotational scanning through the use of two bimorph actuators.
Abstract: This paper reports a novel large vertical displacement (LVD) microactuator that can generate large piston motion and bi-directional scanning at low driving voltage. A LVD micromirror device has been fabricated by using a unique deep reactive ion etch (DRIE) post-CMOS micromachining process that simultaneously provides thin-film and single-crystal silicon microstructures. The bimorph actuation structure is composed of aluminum and silicon dioxide with an embedded polysilicon thermal resistor. With a size of only 0.7 mm × 0.32 mm, the LVD micromirror demonstrated a vertical displacement of 0.2 mm at 6 V dc. This device can also be used to perform bi-directional rotational scanning through the use of two bimorph actuators. The micromirror rotates over ±15 ◦ at less than 6 V dc, and over ±43 ◦ (i.e., >170 ◦ optical scan angle) at its resonant frequency of 2.6 kHz.
TL;DR: In this paper, a silicon resonant torsional micro-mirror excited by piezoelectric bimorph actuators is presented, which achieves optical beam scanning with large angular deflection at high frequency.
Abstract: A silicon resonant torsional micro-mirror excited by piezoelectric bimorph actuators is presented. The bimorph actuators consist of a single-crystal silicon flexible beam or membrane and a PZT thin film. The mechanical elements are etched in the 20 μm thick superficial layer of a SOI substrate, thereby ensuring the flatness of the 500 μm-diameter gold-coated mirror. This device achieves optical beam scanning with large angular deflection at high frequency. In air, we have measured scanning up to 19.8° at 1.8 kHz, 99.1° at 10.6 kHz and 40.8° at 25.4 kHz. The applied driving voltage is sinusoidal with an amplitude under 42 V PP and with a 6 V DC bias voltage. At large oscillation amplitude, a non-linear hard-spring effect has been observed. In vacuum, a 78° optical scanning has been obtained with less than 1 V PP .
TL;DR: In this paper, a 3D hydro-focusing micro cell sorter for micro flow cytometry applications is described, which was microfabricated by means of SU-8 3D lithography.
Abstract: This paper details a novel three-dimensional (3D) hydro-focusing micro cell sorter for micro flow cytometry applications. The unit was microfabricated by means of SU-8 3D lithography. The 3D microstructure for coaxial sheathing was designed, microfabricated, and tested. Three-dimensional hydrofocusing capability was demonstrated with an experiment to sort labeled tanned sheep erythrocytes (red blood cells). This polymer hydro-focusing microstructure is easily microfabricated and integrated with other polymer microfluidic structures. Keywords: SU-8, three-dimensional hydro-focusing, microfluidic, microchannel, cytometer
TL;DR: In this article, the fundamental nonlinear mechanical effects in micromachined single-crystal silicon resonators are investigated in terms of nonlinear engineering Young's modulus that incorporates both geometrical and material effects.
Abstract: The fundamental nonlinear mechanical effects in micromachined single-crystal silicon resonators are investigated. Longitudinal mode beam resonators are chosen for the analysis due to their simple geometry and high quality factor ( Q > 100 000 ). Analytical model for the resonator is developed in terms of nonlinear engineering Young’s modulus that incorporates both geometrical and material effects. For comparison with the theory, beam resonators were fabricated in two different crystalline directions. The measured nonlinearity is larger for beams in [1 1 0] direction than for beams in [1 0 0] direction in agreement with the theoretical prediction. The results provide a quantitative value for the appearance of the material-induced nonlinear effects in single-crystal silicon microresonators.
TL;DR: In this paper, the possibilities and properties of multi-wall carbon nanotube (MWNT)-coated quartz crystal microbalance (QCM) as a humidity sensor are presented.
Abstract: The possibilities and properties of multi-wall carbon nanotube (MWNT)-coated quartz crystal microbalance (QCM) as a humidity sensor are presented. In order to enhance effectively sensitivity of the sensor, the MWNTs coated on QCM are treated by means of ball milling and hydrogen plasma technique, respectively. The morphology and microstructure of MWNT films were characterized with SEM and TEM. It can be found that the frequency shift of the MWNT-coated QCM linearly decreases with increasing relative humidity over the range of 5–97% RH. The sensors have a response and recovery time of about 60 and 70 s, respectively. The experimental results prove that MWNT-coated QCM are usable as a humidity sensor and as an analytical device.
TL;DR: In this article, the authors describe a system of silicon microneedle electrode arrays for electroporation with integrated temperature and fluidic system for drug delivery for cancer therapy, where the fabrication process for a drug delivery system with silicon micro-droneedle electrodes is presented.
Abstract: This paper describes a system of silicon microneedle electrode arrays for electroporation with integrated temperature and fluidic system for drug delivery. In this research we have developed microneedle fabrication processes in standard silicon wafer utilizing wet and dry etch technologies. A method to manufacture electrodes and temperature sensors on the bottom of the microneedle array allows monitoring of temperature changes during electroporation close to the tissue. These local metal pads with interconnections for voltage supply have been realized by employing thick photoresist technologies combined with sputtering. This approach enables the fabrication of microneedle electrode arrays with integrated sensors for cancer therapy. Hollow microneedles allow drug delivery during electroporation. A uniform drug release through hollow microneedle electrodes into tissue improves the injection of drugs and therefore the efficiency of the treatment. The design of the fluidic system was simulated using CoventorWare to ensure the uniform release of fluid volume on every hollow needle. The fabrication process for a drug delivery system with silicon microneedle electrodes is presented.