Search

The movement patterns appropriate for exercise and manual labor do not always correspond to what people instinctively choose for better comfort. Without expert guidance, people can even increase the risk of injury by choosing a comfortable posture rather than the appropriate one, notably when lifting objects. Even in situations where squatting is accepted as a desirable lifting strategy, people tend to choose the more comfortable strategy of stooping or semisquatting. The common approach to correcting lifting posture, immobilizing vulnerable joints via fixation, is insufficient for preventing back injuries sustained from repetitive lifting. Instead, when lifting small but heavy objects, the entire kinetic chain should cooperate to achieve a series of squat-lifting patterns. Inspired by the observation that force fields affect the coordination of voluntary human motion, we devised a passive exosuit embedded with a body-powered variable-impedance mechanism. The exosuit adds impedance to the human joints according to how far the wearer's movement is from the squat-lifting trajectories so that it hinders stooping but facilitates squatting. In an experiment that entailed lifting a small 10-kg box, 10 first-time users changed their voluntary lifting motion closer to squatting on average. Simulation results based on recorded kinematic and kinetic data showed that this postural change reduced the compression force, shear force, and moment on the lumbosacral joint. Our work demonstrates the potential of using an exosuit to help people move in a desirable manner without requiring a complicated, bulky mechanical system.

Customization is an important issue for assistive gloves because it affects glove performance. In this letter, we propose an assembly based customizable soft pneumatic assistive glove, named Exo-Glove PM. Pneumatic soft robots generally consist of a single structure with embedded actuators. However, when assembled, the region where the assemblies are connected easily undergoes large stress concentration that leads to failure. To overcome this issue, we have developed a hybrid actuator module that combines a soft actuation structure and rigid joining methods. In general, rigid joining methods require a bulky design to enable easy assembly, but Exo-Glove PM is designed to create pathways for assembly tools to access the bolt heads by bending certain parts. This novel way of joining assemblies allows soft robots to be built of multiple parts while minimizing the volume. It ensures small module size and enables modules to cover a wide range of hand sizes; the distance between each module is matched to the length of the user's phalanges using spacers. This approach allows users to customize the glove by assembly of standardized modules and maximizes the comfort and the performance of the glove without custom manufacturing and, thus, reduces costs.

Small mobile robots with transformable wheels have recently emerged thanks to their increased mobility and maneuverability. When a high payload is applied to these robots, however, wheel transformation becomes difficult because they must directly overcome the payload’s weight. In this paper, we propose a wheel that can be transformed from its starting circular shape (radius, 56 mm) to a wheel with three legs (radius, 99 mm) under a high payload with low operating force. The key design principle of this wheel is to kinematically decoupled legs and passive locking. Its legs are kinematically decoupled but operated by a single air pump using a pneumatic channel connected to soft pneumatic actuators installed at each leg. Application of pressure causes the legs to behave like a coupled system through the pneumatic channel. With pressurization, the two legs that are not in contact with the ground easily emerge from body, and the leg in contact with the ground emerges once the wheel rotates. Once emerged, each leg is supported by a rigid pawl instead of by the soft pneumatic actuators. This setup enables the legs to be transformed independently with low air pressure, even under high payloads. It reduces system weight and the energy required to maintain the transformed shape. This legged wheel can overcome obstacles up to 2.9 times the radius of the wheel in its circular form, and wheel transformation can be accomplished with 85 kPa air pressure for payloads up to 1115 g.

A Gram reaction-negative, strictly aerobic, non-motile, translucent and rod-shaped bacterium (designated W1-2-4(T)) isolated from tap water was characterized by a polyphasic approach to clarify its taxonomic position. Strain W1-2-4(T) was observed to grow optimally at 25-30 °C and at pH 6.5 on nutrient agar. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain W1-2-4(T) belongs to the genus Sphingomonas and is most closely related to the Sphingomonas fennica K101(T) (95.3 % similarity). The G+C content of genomic DNA was 67.1 mol%. Chemotaxonomic data [major ubiquinone-Q-10, major polyamine-homospermidine, major fatty acids-summed feature 8 (comprising C18:1 ω7c/ω6c), C16:0 and C14:0 2OH] supported the affiliation of strain W1-2-4(T) to the genus Sphingomonas. Strain W1-2-4(T) could be differentiated genotypically and phenotypically from the recognized species of the genus Sphingomonas. The novel isolate therefore represents a novel species, for which the name Sphingomonas hankyongensis sp. nov. is proposed, with the type strain W1-2-4(T) (=KACC 18308(T) = LMG 28595(T)).

We propose a two-dimensional (2-D) in-plane micro-needle array with shaft sidewalls aligned parallel to the vertical (111) crystalline plane of (110) silicon. Six types of needle tips with various shapes and tapered angles were fabricated so as to maintain the tip sharpness. Two layers of micro needles (upper and bottom needle arrays) for the 2-D array were realized using simultaneous etching from the front and back sides of (110) silicon. In addition, microfluidic components were embedded in the micro-needle chip to inject or extract biochemical samples. The length of the micro needles was easily extended to 2200 μm, and the insertion forces of the single and arrayed micro needles were evaluated by pricking chicken breast flesh. In case of a micro needle having a tapered angle of 10° and tip end width of 1 μm, the insertion force per needle was as low as 15 mN, which is lower than those reported in previous studies.

We propose a new capacitive microinclinometer where oblique comb electrodes and double-folded suspension springs are aligned parallel to the vertical (111) plane of (110) silicon. The oblique comb utilizes both the overlapped area and the gap between movable and stationary electrodes, resulting in a considerable increase in sensitivity (capacitance change/angle). The resolution becomes even higher by taking advantage of the smooth (111) sidewalls of the oblique comb electrodes, which are fabricated using silicon deep reactive ion etching followed by crystalline wet etching. The surface roughness was reduced from 200 (Rrms) to 20 nm (Rrms), and the verticality was improved from 88.7° to 89.7°. The capacitance change of the fabricated inclinometer experimentally ranges from -0.793 to 0.783 pF for the full range of inclination angle (from -90° to 90°). The estimated worst resolution, which is obtainable at an inclination angle of ±85°, was as low as 0.25°.

A novel fiber optic surface plasmon resonance (SPR) sensor using cyclic olefin copolymer (COC) prism with the spectral modulation is presented. The SPR sensor chip is fabricated using the SU-8 photolithography, Ni-electroplating and COC injection molding process. The sidewall of the COC prism is partially deposited with Au/Cr (45/2.nm thickness) by e-beam evaporator, and the thermal bonding process is conducted for micro fluidic channels and optical fibers alignment. The SPR spectrum for a phosphate buffered saline (0.1.M PBS, pH.7.2) solution shows a distinctive dip at 1300.nm wavelength, which shifts toward longer wavelength with respect to the bovine serum albumin (BSA)concentrations. The sensitivity of the wavelength shift is . From the wavelength of SPR dips, the refractive indices (RI) of the BSA solutions can be theoretically calculated using Kretchmann configuration, and the change rate of the RI was found to be . The realized fiber optic SPR sensor with a COC prism has clearly shown the feasibility of a new disposable, low cost and miniaturized SPR biosensor for biochemical molecular analyses.

We propose the use of a self-aligned epoxy microbridge with a metal layer for a low-cost, easy-to-make inline fiber optic chemical sensor that can sense the concentration of chemical solutions. The key component of the sensor is a cylindrical epoxy microbridge that can be assembled between input and output optical fibers by self-aligned UV curing. The microbridge is made from an epoxy that can rapidly diffuse liquid. The top of the microbridge was coated with Au/Ti to block diffusion of the surrounding solution and to induce optical dissipation that depends on the concentration of the chemical solution. We tested our fiber optic chemical sensor for deionized (DI) water and NaCl solution. The medium surrounding the microbridge asymmetrically diffuses into the epoxy microbridge due to the metal layer. The asymmetrical diffusion, consequently, makes a major change to the refractive index on the bottom of the microbridge, thereby altering the propagation mode of light. As a result, depending on the concentration of the NaCl solution, a fraction of the propagated light is absorbed into the metal layer. The sensitivity, which refers to the ratio of the concentration change and optical power, was experimentally confirmed to be 0.103 (wt%/photon count)

The present study aims at obtaining a novel fabrication method to realize smooth vertical sidewalls for optical micro/nanoelectromechanical system applications. To reduce the surface defects of the vertically etched sidewall, KOH crystalline etching is employed after silicon deep reactive ion etching process of a (1 1 0) silicon-on-insulator wafer. The effects of additional KOH etching on the sidewall morphology are investigated with respect to the etching temperature and concentration of KOH. The optimized process conditions of KOH etching are found to be 45 wt.% KOH concentration and 70 °C temperature. To evaluate the morphological characteristics of the vertical sidewall, optical resonators consisting of a single silicon plate are fabricated using an optimized process with additional KOH crystalline etching. The experimental effective finesse of the fabricated optical resonator is compared with theoretically simulated finesse and is found to be improved by 21.8% compared with a reference sample fabricated only by the deep reactive ion etching process.

This paper presents a micromachined in-plane tunable optical filter using the thermo-optic effect of crystalline silicon. The device was fabricated by a silicon deep reactive ion etching process with a silicon-on-insulator wafer and thermal oxide removal to improve the sidewall smoothness. Optical fibers could be horizontally aligned on the fabricated TOF device by exploiting in-plane device structures, which enable TOFs to easily connect with other optical components. Tunability of the TOFs was experimentally achieved through thermal modulation of optical path length by heating the silicon etalon. As the input voltage increases, a notch in the reflectance spectrum shifts to a longer wavelength with an average tuning sensitivity of 0.9 nm K−1 and a best bandwidth of 1.1 nm. The proposed device can be utilized for spectroscopy or optical communication.

We have designed and characterized a novel micromachined variable optical attenuator (VOA) with a silicon optical wedge (SOW). Micromachined VOAs are being studied for effective signal balancing and device protection on a wavelength division multiplexing (WDM) network system. Several micromachined optical attenuators have been introduced using an optical shutter between two optical fibers. This reflective shutter in previous micromachined VOAs requires a troublesome sidewall metal coating to block out a part of the incident light signal. In this paper, we report on detailed design strategy and the characteristics of a refractive VOA with a wedge-shaped silicon microstructure. The proposed VOA is optimally designed to successively dissipate a blocked optical power by partial transmission and refraction outside the acceptance angle of the output fiber. The device can be simply fabricated using silicon-on-insulator (SOI) wafers and deep reactive ion etching (DRIE) without a sidewall metallization process. The fabricated VOA showed high performances, such as low insertion loss of 0.6 dB, wide attenuation range of over 43 dB with an optical response time of 6 ms. Return loss was experimentally obtained as high as 38 dB with beveled optical fibers even in an air-ambient condition. In the reliability test, the time-dependent loss (TDL), wavelength-dependent loss (WDL) and polarization-dependent loss (PDL) were measured as 0.08, 0.5 and 1.1 dB, respectively, for the attenuation level of 10 dB, and both WDL and PDL were considerably improved by the thermal oxidation and oxide removal in a high attenuation level.

We report on a novel refractive variable optical attenuator with a wedge-shaped silicon optical leaker, in which a part of the light signal is successively transmitted and refracted outside the acceptance angle of the output fiber. This device can be simply fabricated using a deep reactive ion etching and does not require sidewall metallization. We have theoretically estimated its optical characteristics and experimentally showed its high performances, such as low insertion loss of 0.6 dB and wide attenuation range of 43 dB. The fabricated device also showed a high return loss of over 39 dB even in an air-ambient condition and its polarization-dependent loss was smaller than 10% of the attenuation level.

This paper presents a mechanical cell lysis microfluidic chip with an ultra-sharp nano-blade array fabricated by simple and cost effective crystalline wet etching of (110) silicon. The ultra-sharp nano-blade array is simply formed by the undercutting during the crystalline wet etching process. The sharpness of the silicon nano-blade is less than 10 nm after the undercutting. EL4 mouse T-lymphoma cells are used for the demonstration of the mechanical lysis chip, and the cells are easily disrupted by the silicon nano-blade array without helping of additional reagents or electrical sources. The time-resolved observation of the mechanical cell lysis shows that the developed silicon nano-blade array is enough to easily disrupt the cell membrane even at very low flow rate of 0.7 µl/hr.

In this research, simple crystalline wet etching of (110) silicon is employed to fabricate an in-plane silicon microneedle chip, which is composed of microneedle tips, microchannels and reservoir. The required penetration forces to insert the fabricated microneedles into the skin of chicken breast flesh without failure were 70 mN (500 µm in displacement) and 250 mN (2 mm in displacement) for a single tip and five tips, respectively.

A novel high resolution micro capacitive inclinometer has been developed using (110) silicon. KOH crystalline wet etching was employed after silicon deep reactive ion etching (DRIE) to reduce morphologic defects on the sidewalls of oblique comb electrodes aligned parallel to vertical {111} plane. Suspension springs are also parallel to other vertical {111} plane to secure the width during KOH wet etching. The sensitivity (pF/°) was increased because the oblique comb electrodes change both the overlapped area and gap during operation. The capacitance changed from -0.8 to 0.8 pF for -90° -90° and resolution was estimated at 0.18° or less for ±80°.

A micromachined capacitive inclinometer has been developed to detect inclination angles for a position sensing application. In order to enhance resolution, a (110) crystalline silicon-on-patterned-insulator (COPI) process has been proposed to remove the morphologic defects such as footing and scalloping which were formed from silicon deep reactive ion etching (DRIE) process. The sidewalls fabricated by the (110) COPI process remarkably became vertical and flat with few nanometer roughness. The micro inclinometer with flat and vertical sensing electrodes was evaluated in terms of capacitance change and detection limit. The capacitance change of the fabricated device is from -0.246 to 0.258 pF for the inclination angle (-90deg to 90deg). The temporal deviation of the capacitance is as small as 0.2 fF, which leads to 0.3 or less resolution for plusmn70deg.

A micro-plasma generator for the detection of heavy metals in the water has been fabricated and evaluated. As for the new type of a plasma source, the micro-plasma generator based on water electrode has been proposed. This type of device features simple device structure that doesnpsilat require nebulizer for water samples. Water sample is isolated from a metal electrode by glass substrate, eliminating unexpected side effects such as electrophoresis and electrochemical reaction between a metal electrode and ions in water. This configuration prevents metal electrodes from erosion, which will lead to high detection reliability for water contaminants. The lead (Pb) in nitric acid solution (0.1 M) was detected using the fabricated micro-plasma generator and a fiber optic spectrometer. Two atomic emission lines of the lead (at 368 nm, 405 nm) were clearly observed. 10 ppm of Pb ions in nitric acid solution was measured using the proposed micro-plasma generator based on water electrode.

We have developed a simple assembly technology to realize the tilted vertical combs for electrostatic micromirror scanners. The in-plane vertical comb electrodes are easily transformed into out-of-plane tilted comb by asymmetrical pushing down the levers of the spring that is attached to the micro mirror. The fabricated mirror scanner showed the optical scan angle of up to 1.3deg at 60 V and the resonant frequency of 3.15 kHz.

A bio-MEMS based cell-chip that can detect a specific toxicity was fabricated by patterning and immobilizing bioluminescent bacteria in a microfluidic chip. Since the emitted light intensity of bioluminescent bacteria changed in response to the presence of chemicals, the bacteria were used as the toxicity indicator in this study. A pattern of immobilized cells was successfully generated by photolithography, utilizing a water-soluble and negatively photosensitive polymer, PVA-SbQ (polyvinyl alcohol-styrylpyridinium) as an immobilization material. Using the recombinant Escherichia coli (E. coli) strain, GC2, which is sensitive to general toxicity, the following were investigated for the immobilization: an acceptable dose of long-wavelength UV light, the biocompatibility of the polymer, and the effect of the chip-environment. We found that 10 min of UV light exposure, the toxicity of polymer (SPP-H-13-bio), and the other chip-environment did not inhibit cell metabolism significantly for making a micro-cell-chip. Detection of a specific toxicity was demonstrated by simply immobilizing the bioluminescent bacteria, DK1, which increased bioluminescence in the presence of oxidative damage in the cells. An injection of hydrogen peroxide of 0.88 mM induced 10-fold increase in bioluminescent intensity confirming the capability of the chip for toxicity monitoring.

We describe a low cost, simply fabricated in-line fiber optic chemical sensor with gold coated, self-aligned epoxy waveguide for sensing the concentration of chemical solutions

This paper presents crystalline Si-based tunable Fabry-Perot filter, which enables its integration to align with other optical devices on an in-plane substrate. This device features wide tuning range over 80 nm and high tuning sensitivity of 11.7 nm/V.

In an optical wavelength division multiplexed (WDM) telecommunication system, optical add-drop multiplexers (OADM) with optical switches have been researched to change the paths of the signals. This paper reports on the design and characterization of a micromachined 2×2 optical switch aligned with 4 beveled fibers for low return loss in an optical add-drop application. For driving the micro mirror to change the optical paths an electrostatic comb actuator is used. The experimental return losses and polarization dependent loss were -43 and 0.05 dB, respectively.

Presents a new micromachined VOA with a wedge-shaped silicon optical leaker blocking and successively dissipating optical signal. This device features large attenuation range of -38 B, return loss of -40 dB and low cost owing to no troublesome sidewall metallization.

This paper presents, for the first time, a micromachined in-plane tunable optical filter (TOF) using thermo-optic effect for wavelength division multiplexed telecommunication. The TOFs are comprised of a Fabry-Perot silicon optical resonator formed between two distributed Bragg reflectors with high-reflectance based on silicon/air-gap pairs. The whole device was vertically fabricated using silicon deep reactive ion etching (DRIE). And input/output optical fibers were easily aligned along with the TOF structure on the substrate by exploiting in-plane fiber alignment. Tunability of the TOFs is experimentally achieved through thermal modulation of optical path length by heating the silicon resonator. As an input voltage increases, a notch of reflectance spectrum shifts to a longer wavelength with a tuning range of 9 nm and 3dB bandwidth of 2nm. The temperature of a silicon resonator was estimated to be about 93°C for the tuning range.

This paper presents a novel fabrication method of scalloping-free and footing-free vertical electrodes for micromachined capacitive inclinometers with a high sensing resolution. The proposed fabrication method is based on additional crystalline wet etching of a (1 1 0) silicon that is bonded to a silicon substrate with a patterned insulator layer. The sensing electrodes, which are aligned to the (1 1 1) plane, have very smooth sidewalls because the morphological defects formed by the silicon deep reactive ion etching (DRIE) process are drastically reduced in the crystalline wet etching. The fabricated capacitive inclinometer with smooth sensing electrodes was evaluated in terms of capacitance change and resolution. The capacitance of the fabricated inclinometer is changed from −0.246 to 0.258 pF for the inclination angle (−90° to 90°). The temporal deviation of the capacitance is as small as 0.2 fF, which leads to a high resolution of 0.1° or less for ±45°.

This study presents a fabrication method of a mass-producible silicon nanowire (SiNW) using a (1 1 0) silicon wafer. Microscale silicon lines, patterned in standard photolithography, are reduced to 300 nm in width in a two-step wet-etching process. The silicon lines are transformed into the SiNW by a thermal oxidation process. The formation of SiNW after thermal oxidation was verified using a numerical oxidation simulation considering the two-dimensional growth of the oxide. After thermal wet oxidation at 970 °C for 50 min, silicon lines of 300 nm in width were transformed into the SiNWs of an inverse triangular cross-section with an effective width of approximately 70 nm. At the same time, the fabricated SiNWs were electrically isolated from the substrate without using an expensive silicon-on-insulator wafer. The pH sensing test, which is usually performed as a preliminary experiment for the biosensor applications, was conducted with respect to various pH solutions. The experimental sensitivity to the pH level was 0.55 nS pH−1, when the voltage applied to the SiNW was 1 V. The SiNW has been completely fabricated by using only a conventional semiconductor process instead of a costly and time-consuming e-beam lithography process for the nanoscale patterning. The proposed fabrication method was successfully confirmed to have the potential of mass-producible and cost-effective SiNW devices for nano-biosensor applications.

We design, fabricate, and characterize the micromachined refractive variable optical attenuator (VOA) with a wedge-shaped silicon optical leaker (SOL). The vertical structures of the VOA device can be simply fabricated by deep reactive ion etching with no sidewall metallization, and the 8 degrees angled fibers are employed for a high return loss even in air-ambient conditions. The SOL successively transmits and refracts part of the incident light far outside the acceptance angle of the output fiber, showing an effective optical attenuation. The fabricated VOA gives high optical performances, such as a response time of 6 ms, a return loss of 39 dB, an insertion loss of 0.6 dB, an attenuation range of 43 dB, and a polarization-dependent loss (PDL) of a 10% attenuation level, including a wavelength-dependent loss. The optical characteristics of the VOA are also theoretically investigated with respect to the wedge angles of the SOL. The experimental characteristics are in good agreement with the theoretical values calculated, considering light scattered from the endface of an optical fiber and sidewall of the SOL. The PDL estimation was confirmed especially to sufficiently explain the fundamental characteristic of the PDL for the refractive VOA.