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Silicon nanostructures can improve the bending strength of wafers, but often trap particle contaminates. A double-sided surface nanostructure with a morphology controlled via wet chemical etching is used to both improve the mechanical strength and reduce surface reflection. Compared with a conventional polished silicon wafer, the bending strength was increased by 3.4 times and the surface reflection was reduced to 1%, and so can provide a promising solution for photovoltaic applications. The optically unused side of the wafer was protected by a thin silicon layer that prevented the entrapment of particles that might cause glitches in subsequent fabrication processes, all the while maintaining the enhancement in strength. The particle test confirmed that incorporating protection layer intacts the particle count with polished silicon sample.

The strawberry (Fragaria &times, ananassa Duch.) is a high-value crop with an annual cultivated area of ~500 ha in Taiwan. Over 90% of strawberry cultivation is in Miaoli County. Unfortunately, various diseases significantly decrease strawberry production. The leaf and fruit disease became an epidemic in 1986. From 2010 to 2016, anthracnose crown rot caused the loss of 30&ndash, 40% of seedlings and ~20% of plants after transplanting. The automation of agriculture and image recognition techniques are indispensable for detecting strawberry diseases. We developed an image recognition technique for the detection of strawberry diseases using a convolutional neural network (CNN) model. CNN is a powerful deep learning approach that has been used to enhance image recognition. In the proposed technique, two different datasets containing the original and feature images are used for detecting the following strawberry diseases&mdash, leaf blight, gray mold, and powdery mildew. Specifically, leaf blight may affect the crown, leaf, and fruit and show different symptoms. By using the ResNet50 model with a training period of 20 epochs for 1306 feature images, the proposed CNN model achieves a classification accuracy rate of 100% for leaf blight cases affecting the crown, leaf, and fruit, 98% for gray mold cases, and 98% for powdery mildew cases. In 20 epochs, the accuracy rate of 99.60% obtained from the feature image dataset was higher than that of 1.53% obtained from the original one. This proposed model provides a simple, reliable, and cost-effective technique for detecting strawberry diseases.

The output power of conventional light-emitting diodes (LEDs) is enhanced by 9% at 120 mA current without alterations to the existing fabrication techniques and to the multi-quantum well (MQW) junction. The output power is improved by nanotexturing the street of the n-gallium nitride (GaN) layer that was unexploited, for the enhancement of the optical or electrical properties. The nanotextured street enhances the light extraction exclusively near the street of the n-GaN layer by reducing the reflections from the LED surface. Similar light output patterns and I–V characteristics for LEDs with and without street nanotexturing were observed, confirming that the enhanced light extraction has been achieved without a change in the spatial distribution of light or in the properties of the MQW junction. A new approach for the output power enhancement of all types of existing LEDs is provided.

This paper presents a novel tactile sensing array with adjustable sensing range and sensitivity. The sensing array consists of a deformable PDMS spacer layer, two Al glass substrates, and two dielectric liquids. The two dielectric liquids form a composite dielectric material, which is a low-dielectric-constant (ɛr) droplet covered with a high-ɛr liquid. The composite dielectric material is sandwiched between the upper and lower electrodes. By adjusting the electric flux passing through the electrodes, the contact angle of the droplet can be controlled. The sensing range and sensitivity were adjusted by varying the droplet shape. The results show that the device's sensing range can be adjusted in the ranges 0.05–0.29 N and 0.42–1.12 N. Compared with other devices, which are often used in a large force range, this device can be used in a smaller force range and provides 1.88 times greater sensitivity. Besides, the sensitivity can be adjusted during the sensing process.

This letter presents a wafer-level approach for producing rollable single-crystal silicon integrated circuit (IC) wafers, bent with a 17-mm minimum radius of curvature, achieved by backside nanotexturing. The three-point bending test indicates a mechanical strength enhancement by a factor of 2.3 for nanotextured 60- $\mu \text{m}$ thick samples. The minimum radius of curvature decreased by 43.4%, exhibiting improved flexibility. The carrier charge mobility increases by 4.9%, 12.6%, and 16.9% for the bending radii of 45, 30, and 24 mm, respectively. The increment of the mobility corresponds with the changing compressive stress in p-MOSFETs fabricated on the IC wafer.

Photovoltaic, microelectromechanical systems, and integrated circuit industries are demanding a technology to enable the high rupture resistant silicon wafer production to improve the manufacturing yield. The presented silicon nanotexture patterning on the edges and sidewalls by wet chemical etching process can protect single-crystalline and multicrystalline silicon samples from rupture. Bending tests indicate a mechanical strength enhancement of ~ 72%-75% for sc-silicon and ~71%-73% for mc-silicon samples. In addition, the front and back surfaces of the samples remain intact and appropriate for any further semiconductor processes. This technology was implemented in solar cells that exhibited a strength improvement of nearly 73% without affecting their photovoltaic performances, anticipating an effective solution for the solar cell manufacturing industry.

In this study, we mechanically strengthened a borosilicate glass wafer by doubling its bending strength and simultaneously enhancing its transparency using surface nanostructures for different applications including sensors, displays and panels. A fabrication method that combines dry and wet etching is used for surface nanostructure fabrication. Specifically, we improved the bending strength of plain borosilicate glass by 96% using these surface nanostructures on both sides. Besides bending strength improvement, a limited optical transmittance enhancement of 3% was also observed in the visible light wavelength region (400–800 nm). Both strength and transparency were improved by using surface nanostructures of 500 nm depth on both sides of the borosilicate glass without affecting its bulk properties or the glass manufacturing process. Moreover, we observed comparatively smaller fragments during the breaking of the nanostructured glass, which is indicative of strengthening. The range for the nanostructure depth is defined for different applications with which improvements of the strength and transparency of borosilicate glass substrate are obtained.

Defects and heterogeneities degrade the strength of glass with different surface and subsurface properties. This study uses surface nanostructures to improve the bending strength of glass and investigates the effect of defects on three glass types. Borosilicate and aluminosilicate glasses with a higher defect density than fused silica exhibited 118 and 48 % improvement, respectively, in bending strength after surface nanostructure fabrication. Fused silica, exhibited limited strength improvement. Therefore, a 4-μm-deep square notch was fabricated to study the effect of a dominant defect in low defect density glass. The reduced bending strength of fused silica caused by artificial defect increased 65 % in the presence of 2-μm-deep nanostructures, and the fused silica regained its original strength when the nanostructures were 4 μm deep. In fragmentation tests, the fused silica specimen broke into two major portions because of the creation of artificial defects. The number of fragments increased when nanostructures were fabricated on the fused silica surface. Bending strength improvement and fragmentation test confirm the usability of this method for glasses with low defect densities when a dominant defect is present on the surface. Our findings indicate that nanostructure-based strengthening is suitable for all types of glasses irrespective of defect density, and the observed Weibull modulus enhancement confirms the reliability of this method.

Backside nanotexturing fabricated by electroless metal assisted wet chemical etching, protected with a deposited thin silicon layer, is a new approach to create high bending strength silicon samples. Bending strength for protected nanotextured samples followed by CMP process was enhanced by ∼3.4 folds as compared to polished silicon samples, which emphasize the possibility of industrial implementation. The morphology of silicon deposition layer upon nanotexture influences the stress behavior, which need an adequate fabrication technique for uniform deposition at wafer scale. The thin protection layer upon nanotexture prevents the unwanted particle trapping, which affects the electrical performances of the device. Moreover, this technology provides a rupture resistive solution for IC, MEMS and photovoltaic devices for industrial implementation.

A prototype of a profilometer was built with the technique of composite interferometry for measurement of the distribution of both the amplitude and phase information of the surface of a material simultaneously. The composite interferometer was composed of a Michelson interferometer for measuring the surface profile of the sample and a Mach–Zehnder interferometer for measuring the phase deviation caused by the scanning component and environmental perturbations. A high-sensitivity surface profile can be obtained by use of the phase compensation mechanism through subtraction of the phases of the interferograms detected in the two interferometers. With the new design and improvement of robustness of the optical system, the measurement speed and accuracy were significantly improved. Furthermore, an additional optical delay component results in a higher sensitivity of the interference signal. This prototype of vibration-immune profilometer was examined to have a displacement sensitivity of 0.64 nm.

We proposed and demonstrated an optical delay line composed of all reflective components for long-range scanning without walk-off problem. The optical delay line consists of a retro-reflector, an inclined reflection mirror and a scanning mirror. The size of the optical delay line is within 2 cm × 2 cm and the scanning range can reach 2.9 mm when the beam is incident at the pivot of the scanning mirror and the vibration angle of the scanning mirror is 9.6°. The scanning range can be further increased when the pivot of the scanning mirror is laterally deviated from the incident beam. The optical delay line possesses the advantages that it is compact, easy to fabricate and can perform rapid scanning in large scanning range without walk-off problem. The optical delay line was demonstrated with a low-coherence reflectometer where the scanning rate was 400 Hz. A higher scanning rate can be achieved when a scanning component with higher scanning rate is applied.

This study employed a Taguchi-based experimental design to determine the experimental layout and optimal machining parameters for stress concentration in the microdrilling of titanium alloy. The finite element method (FEM) was used to analyze the characteristics of stress concentration in microdrilled holes. The signal-to-noise (S/N) ratio and analysis of variance (ANOVA) were employed to determine the optimal levels and the order of significance of the identified critical parameters affecting stress concentration. The critical control parameters in this study included rotational speed (rpm), feed rate (mm/min), cutting fluid, and holding length (mm). Results show that finite element simulation can effectively analyze the stress concentration of microholes. The stress concentration factor in a specimen is related to its microhole quality. The maximum stress concentration factor of the drilled hole was 4.46 times that of an ideal hole.

This article reports a side electromechanical instability problem of slender comb-fingers in MEMS electrostatic comb-drive actuators. This instability is induced by two adjacent comb-fingers being excessively bent to contact each other. In this work, based on the assumed shaped energy method, a one degree-of-freedom model was derived to deal with such side pull-in phenomenon of individual fingers. A numerical iterative scheme was introduced to solve for the deflections of fingers from the theoretical model and to predict the side pull-in voltages. FEM simulations were conducted for comparison with the theoretical analyses. Theoretical and simulation results agreed well with each other in the deflections of comb-fingers and pull-in voltages. It was found that in the finger array, each finger exhibits distinct feature; inner fingers show negligible deformation while sided finger are strongly deflected by the transverse electrostatic force. In particular, the first and last fingers show the largest deflections and thus have the highest tendencies to contact adjacent fingers. Moreover, by widening these two fingers, the deflection of every finger can be suppressed. This suggests that the side instability of the comb-fingers is dominated by the first and last fingers. Using the proposed model, the deflection of every individual finger can be calculated and a more reliable design of comb-drive actuator can be achieved.

The unavoidable occurrence of microdefects in silicon wafers increase the probability of catastrophic fracture of silicon-based devices, thus highlighting the need for a strengthening mechanism to minimize fractures resulting from defects. In this study, a novel mechanism for manufacturing silicon wafers was engineered based on nanoscale reinforcement through surface nanotexturing. Because of nanotexturing, different defect depths synthetically emulated as V-notches, demonstrated a bending strength enhancement by factors of 2.5, 3.2 and 6 for 2-, 7- and 14-μm-deep V-notches, respectively. A very large increase in the number of fragments observed during silicon fracturing was also indicative of the strengthening effect. Nanotextures surrounding the V-notch reduced the stress concentration factor at the notch tip and saturated as the nanotexture depth approached 1.5 times the V-notch depth. The stress reduction at the V-notch tip measured by micro-Raman spectroscopy revealed that nanotextures reduced the effective depth of the defect. Therefore, the nanotextured samples were able to sustain a larger fracture force. The enhancement in Weibull modulus, along with an increase in bending strength in the nanotextured samples compared to polished single-crystal silicon samples, demonstrated the reliability of the strengthening method. These results suggest that this method may be suitable for industrial implementation.

In this work, we present a novel viscometer array based on dynamic response of droplets driven by dielectric force. Each sensing element contains a small testing droplet (3 µL) sandwiched by upper and lower electrodes. When applying a bias voltage between the electrodes, the droplet changes its shape due to the dielectric force, causing capacitance change between the upper and lower electrodes. The viscosity of the droplet was measured from the time constant of the step response. The results show the sensing range of viscometer array is 10 cSt to 200 cSt less than 1000 ms.

A method for extending displacements of comb drive actuators has been demonstrated in this paper. Differing from other methods which modify the shape of suspension to shift the maximum of the lateral spring constant curve, or adjust the lengths of the individual comb fingers to reduce the equivalent electrostatic spring constant, this method changes the configuration of comb electrodes to shift the minimum of the equivalent spring constant curve. In addition to the original set of comb electrodes, a set of secondary comb electrodes was added into a comb drive actuator. By sequentially powering these two sets of electrodes, the comb drive can acquire more displacement than the original. The feasibility of this method was examined based on the existing theories and simulation software. An inequality that predicts the extending displacement after using this method was given. Based on this inequality, additional displacement could be achieved by adding one set of secondary comb electrodes and switching them sequentially. In our experiment, a case with 40.6% additional displacement has been observed. This value is consistent with the result derived by the model presented in this paper.

A new method is proposed to improve thin-film stress measurement using micromachined bilayer cantilevers. Our previous studies demonstrated that the width does affect the bilayer cantilever deflection, and the effect of width disappears as the width exceeds a critical value, which is usually far larger than the bilayer cantilever length. The existing methods, which employ the narrow micromachined bilayer cantilever to measure the residual stresses, do not consider the width effect, and hence may generate some uncertainties in their measurement results. To remove these uncertainties, a cantilever with a very large width is introduced and used in this proposed method. Its corresponding model, based on the plate theory, has been derived and applied to this new measurement procedure. Following the measurement procedure suggested in this paper would provide measurement results more reliable than the traditional ones which use the narrow bilayer cantilever in determining the stresses of thin films.

In this paper, the effect of cantilever width is demonstrated on the stress-induced bending of micromachined bilayer cantilevers. In previous literature, the bilayer cantilever has been modeled as a two-dimensional structure; consequently, the stress-induced bending of micromachined bilayer cantilever was considered to be independent upon the width. In this study, the fabrication and characterization of various widths of micromachined bilayer cantilever have been performed to observe the out-of-plane deformation caused by residual stresses. A finite element model has been established to analyze such a deformation. With the support of experimental and numerical results, width dependence in the stress-induced bending of micromachined bilayer cantilever has been discussed. As a result, the tip deflection of the bilayer cantilever gradually increases as the width increases until the width-to-length ratio reaches a critical value, in which the micromachined bilayer cantilever can be regarded as an infinitely wide cantilever, and any cross section along the length is in plane strain state. Furthermore, width-independent design, which exists among very wide cantilevers with various widths, has also been reported. Thus a more reliable design can be achieved.

Bending strength of single-crystalline silicon (sc-Si) substrates enhanced by forming silicon nanowires (SiNWs) on the surfaces has been investigated for the application of sc-Si solar cells. As operated under the three-point-bending test, the 40-mm-long, 20-mm-wide, and 0.61-mm-thick sc-Si substrates show a high bending strength of 1.02 ± 0.11 GPa and maintain bulk properties. By this strengthening method, a hand-bent 6-in 0.23-mm-thick sc-Si solar cell shows the displacement of 35 mm and the curvature radius of 75 mm. Moreover, the bending strengths of strengthening sc-Si substrates for the SiNW depths of 1, 2, and 4 μm are 2.1, 4.3, and 6 times larger than that of pristine sc-Si substrates (i.e., 0.17 ± 0.01 GPa), respectively.

This paper presents a novel sensing array with tunable sensing ranges for dynamic tactile sensing. Each element in the array contains a droplet with variable shape. By controlling the dielectric force applying on the droplet, the shape of the droplet can be controlled. The sensing range was tuned due to the variation of the droplet shape. This sensing array can be not only used in static tactile sensing but also in dynamic tactile sensing. The experiment result shows the sensing range, from 0.6 N to 1.05 N, can be tuned in 100 ms.

This paper presents a novel tactile sensing array with adjustable sensing ranges. Each sensing element contains a low dielectric constant (er) droplet covered with high er liquid. We controlled the contact angle of the droplet by controlling the electric flux passing through the element. Then, the sensing ranges and sensitivity were also adjusted due to the variation of the droplet shape. The results show the sensor's sensing range is easily adjusted from 0.33N ~ 1.05N to 0.04N ~ 0.60N. And the sensitivity is also adjusted from 1.47pF/N to 2.90.pF/N.

This work presents silicon flapping wings design with higher bending strength and low reflectivity for MEMS aircraft. The design was bio-inspired by the cicada wings which are having numerous nanostructures upon it. The nanostructure on silicon increases the bending strength by ~6 times. The higher strength silicon samples can successfully demonstrate the 100 μm thick bendable silicon by nanostructure surface texturing used for flapping wings. Moreover, same nanostructures act as antireflective layer due to improved light trapping for solar cell. The reflectivity of the nanotextured surface reduces to ~2%.

In this paper, we propose a novel dielectric liquid-based tactile sensor with three axial sensing ability and high sensitivity. The sensor which consists of 3 capacitors uses Polydimethylsiloxane (PDMS) structure to encapsulate two liquids, i.e. a polyalcohol droplet (with higher dielectric constant) and oil (with lower dielectric constant, surrounding). The three axial force signals are detected by the capacitance change due to the mechanical deformations of the capacitors and the position change of the droplet. The proposed sensor's sensitivities in z-, x-and y-axes are 2.02 pF/N, 0.472 pF/N and 0.496 pF/N, respectively. The high sensitivity with promising spatial resolution would satisfy requirements of humanoid robotic applications.

This paper presents a new actuation mechanism to drive comb-drive actuators. An asymmetric configuration of the finger overlap was used to generate capacitive coupling for the actuation mechanism. When the driving voltages were applied on the stators, a voltage would be induced at the rotor due to the capacitive coupling. Then, an electrostatic force would be exerted onto the rotor due to the voltage differences between the stators and the rotor. The actuator’s static displacement and resonant frequency were theoretically analyzed. To verify the design, a comb-drive actuator with different initial finger overlaps, i.e., 159.3 μm and 48.9 μm on each side, was fabricated and tested. The results show that the actuator worked well using the proposed actuation mechanism. A static displacement of 41.7 μm and a resonant frequency of 577 Hz were achieved. Using the actuation mechanism, no electrical connection is required between the rotor and the outside power supply. This makes some comb-drive actuators containing heterogeneous structures easy to design and actuate.

This paper presents a novel capacitive tactile sensor with high sensitivity for humanoid robots. The main structure of the sensor is a cubic ‘box’ (3 × 3 × 2.5 mm3) made of Polydimethylsiloxane (PDMS). Two dielectric liquids, i.e. a polyalcohol droplet (with a higher dielectric constant) surrounded by oil (with a lower dielectric constant), were sealed in the box under iso-density condition. Electrodes were fabricated on the upper and lower inner surfaces of the box to form a capacitor. The two liquids, sandwiched by the electrodes, increased the capacitance of the capacitor. The sensitivity of the sensor increased due to the novel configuration. The proposed sensor was fabricated by microfabrication technology. This sensor's sensitivity is 61.77%/N, which is 3.3 times greater than that of typical sensors containing no liquid.

In this work, we proposed a hybrid PDMS-silicon electrostatic actuator with a large stroke under low driving voltages. The device features a staggered vertical comb-drive suspended by PDMS springs. Because of the flexibility of PDMS, an initial staggered displacement was naturally formed due to the self-weight of the device. Experimental results showed that the combination of polymeric springs and silicon structures enabled the large stroke of 3.73 µm at 3.5 kHz. The presented heterogeneous integration technology improves the performance and may bring new functionalities to micro-systems.

A cell rotation method by using optoelectronic tweezers (OET) is reported. The binary image of a typical OET device, whose light and dark sides act as two sets of parallel plates with different ac voltages, was used to create a rotating electric field. Its feasibility for application to electrorotation of cells was demonstrated by rotating Ramos and yeast cells in their pitch axes. The electrorotation by using OET devices is dependent on the medium and cells’ electrical properties, the cells’ positions, and the OET device’s geometrical dimension, as well as the frequency of the electric field.

We proposed and demonstrated an optical system for high-speed and high-resolution imaging of surface profiles. The system is a fiber-based composite interferometer in which a Michelson interferometer is used for the measurement of the surface profile of the sample and a Mach-Zehnder interferometer is used for compensation of phase deviation due to the systematic errors and environmental perturbations. In the system, a laser diode with wavelength of 531 nm was used as the light source. A two-axis translation stage was used for lateral scanning of the sample. In the reference arm, a reflection mirror was arranged on a translation stage driven by a piezoelectric transducer as the axial scanning component. The phase difference between the interferograms of both interferometers was acquired to obtain the surface height of the sample. The axial accuracy of ±5 nm was achieved where the imaging was acquired within one minute for a frame. The lateral resolution was at the diffraction limit of light. The system possesses the advantages of low cost, portability and flexibility. Furthermore, it can perform high-resolution imaging in large area without special shielding of the system as well as any special preparation of the sample.

This article presents a side electromechanical instability of slender comb-fingers in MEMS electrostatic devices. Two models are developed for predicting such side pull-in of comb-fingers; one is based in the lumped modeling technique and another is developed by FEM approach. In the slender finger array, the deflection of every finger and pull-in voltage can be calculated by the models. Results indicate every comb-finger bends with different amplitudes. In the finger array, few sided fingers are strongly deflected, the extreme sided fingers in particular, while other inner fingers show negligible deformations. We suggest these extreme sided fingers can dominate the side pull-in of the comb-fingers and should be considered with careful device design by employing the proposed models in this paper.Copyright © 2008 by ASME

Nested folded-beam suspensions with a low longitudinal spring constant and a high lateral spring constant have been used in comb-drive actuators. In the new design, every two flexible beams and two stiff members form a parallelogram flexure, which is considered as an ‘element’ of the nested folded-beam suspension. A set of these flexures of increasing size were placed one outside another to compose a nested structure. In this way, a serial mechanical connection between adjacent parallelogram flexures was formed; thus, a longer output stroke was obtained by combining the stroke displacements of all flexures in an additive fashion. The designed suspensions were theoretically analyzed and numerically simulated. Furthermore, comb-drive actuators with conventional and new suspensions were fabricated and tested to verify the predicted function. In the testing cases, the longitudinal spring constants of suspensions with two (conventional), three and four parallelogram flexures on each side were measured as 2.77, 1.75 and 1.36 N m−1. The ratio among these three values was approximately 6:4:3, which is consistent with the theoretical predictions and simulation results. Microfabricated folded beams in series were achieved.

We proposed and demonstrated a fiber-based composite interferometer, which can perform surface profile measurements with sensitivity at the nanometer scale. With the proposed phase-compensation mechanism, the phase deviation due to the instability of the optical delay component and environmental perturbations can be simultaneously compensated. The measurement sensitivity and imaging speed can be significantly improved such that the system can be used as a high-speed, high-resolution, and wide-field dynamical imaging system. The axial precision of the system was examined to be 0.82 nm. High-resolution time-lapsed dynamical imaging of onion cells during dehydration processes were performed with this system with one frame captured in 75 s.

High quality single-crystalline wurtzite indium nitride (InN) thin film was first demonstrated to have a Young's modulus of 149 ± 5 GPa along a-axis using atomic force microscopy microbending test since the revision of InN energy gap. These released InN cantilever beams were examined to have ignorable in-plane residual stress using micro-Raman spectroscopy, where the E2 (high) mode at 490 cm−1 exists zero shift because of the perfect lattice match (8:9 commensurate) between InN and underneath aluminum nitride buffer. The experimental value of Young's modulus agrees well with a number of theoretical estimations ranging from 146 to 159 GPa.

This study discusses sacrificial bridges that are used to release MEMS devices. Before being released, sacrificial bridges connect all the component structures into an integral structure. Solder bump bonding is used to mount the MEMS chip on another chip or a printed circuit board (PCB) and to maintain the alignment among all component structures after removal of the sacrificial bridges. Two types of sacrificial bridges were designed, analyzed and fabricated. The fabrication process?which used low resistivity single crystal silicon (SCS) wafers as the device material?was developed to implement the sacrificial bridges. Novel SCS through silicon vias (TSVs), which interconnect stacked chips, was made using the same process. An electrostatic comb drive actuator was fabricated and mounted onto a PCB. The fabricated actuator was tested to demonstrate the feasibility of the fabrication process, sacrificial bridges and SCS TSVs. The results show that the actuator worked well. Its maximum displacement and resonant frequency were 69.9 ?m and 406 Hz, respectively. This method is promising for the delivery of a novel 3D system in package for MEMS devices.

The symmetry of the electric field in a dielectric medium sandwiched between comb-fingers dominates the stability of the comb-drive actuator. The stability can be spontaneously broken by the asymmetry appearing on the two sides of the finger array. A quite universal circuit simulator (Qucs) equivalent circuit model was built to illustrate that the symmetry is not preserved in the outer four comb-fingers, especially the first and last fingers, because they are subjected to unbalanced electrostatic forces. Experiments were conducted to verify the proposed Qucs model, which also demonstrated that symmetry exists everywhere in an imaginary comb-finger array with infinite interdigitaed fingers. In this work, the ideal comb-finger array can be nearly realized by making the two outermost fingers five times wider than the others; as a result, the symmetry is preserved and the instability is effectively suppressed in the comb-finger array.

In this paper, a high resolution Vernier-type displacement sensing mechanism is proposed by utilizing Vernier-type suspended gate field-effect transistors (SGFETs), The field-effect transistor benefits from its linear output signal and simple structure, and the concept of Vernier gate is used to enhance the resolution. The displacement of the comb-drive actuator is sensed via the output drain current of SGFET. Design and analysis for Vernier-type suspended gate were presented and some characteristics of the Vernier-type SGFETs were also discussed in simulation results.

This paper reports magnetic microrobots with rolling capability. A magnetic object subjected to an externally rotating magnetic field would be rotated due to the tendency of alignment between its internal magnetization and the field. Based on this principle, a magnetic microrobot in a spherical body with a diameter of several hundred microns was designed and fabricated. To remotely power and control the microrobot, a rotating magnet was used to generate a rotating magnetic field. Driven by this field, the microrobot can freely roll on three-dimensional surfaces. These surfaces can be in air, water or silicon oil. In a dry environment, a microrobot with a diameter of 440 µm achieved a maximum linear speed of 13.2 mm s−1.

It is a challenge to achieve free and efficient motion of microrobots on arbitrary surfaces. We report a rolling locomotion method for a magnetic microrobot with a rectangular body ( 300 × 200 × 50 μ m 3 ) ; this method is based on an external rotating magnetic field. The magnetic force, accompanied by normal and friction forces, enables the successive rotations of the microrobot. A magnetic field with a rotational speed of 2 rps rolls the microrobot, giving it a translation speed of 1.4 mm/s. With this locomotion ability, microrobots can move along a line or curve and can climb slopes or stairs.

An in-plane rotary comb drive actuator was designed for variable optical attenuators (VOAs) that achieved large attenuation with fast response at low driving voltage. Actuator performance was improved by using a higher density of comb fingers for a smaller moment of inertia, serpentine flexure springs for a larger rotational angle, and symmetric spring arrangement for a higher radial shock resistance. A rotation of a tilted reflective mirror was used to further enhance the optical attenuation of VOA. The actuator, proposed with the size of 2 mm×2 mm, achieved the bandwidth of 350 Hz and the deflection angle of 2.5 deg at 5 V, resulting in the maximum attenuation of 57 dB.