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• The deep reactive ion etching (DRIE) of in-plane silicon microneedles is presented. • A needle sharpening process is developed using sacrificial layers (remaining unetched silicon). • The wedge-shaped needle is sharpened to conical structure tapering from the base to the apex. • The sharp microneedles have been demonstrated to be sufficiently robust for skin penetration. The deep reactive ion etching (DRIE) of in-plane silicon microneedles with open capillary microfluidic network is presented. The in-plane needle design allows easy fabrication of long needles for accessing abundant dermal fluids and improves the correlation with blood biomarkers. However, the anisotropic DRIE yields wedge-shaped (not sharp) needle tip. We developed a sharpening process using the sacrificial layers (remaining unetched silicon layer below the needle shaft) to facilitate the buildup of the concentration gradient of the etching species during the wet etching sharpening process, resulting in the relatively fast etching rate at shaft top than the bottom. As a result, the wedge-shaped structure is sharpened to conical structure, tapering smoothly from the base to the apex. Such sharp microneedles have been demonstrated to be sufficiently robust to penetrate porcine skins, with needles being intact after repetitive penetrations. The fabricated silicon devices are treated with oxygen plasma for making the surface hydrophilic, such that the capillary fluid is introduced within the open microfluidic network. [ABSTRACT FROM AUTHOR]

Highlights: [•] Flexible surface-nanostructured SiC film with switchable wetting behavior is presented. [•] The contact angle of super-hydrophobic SiC nano-ball surface achieves to higher than 160°. [•] The contact angle of super-hydrophilic SiC nano-tip surface reduces to below 1°. [•] The switchable wettability was systematically investigated from both physical and chemical mechanisms. [•] The first experimental demonstration of SiC-based surface-enhanced Raman scattering materials is presented. [ABSTRACT FROM AUTHOR]

Abstract: An implantable mechatronic microsystem is a new approach to restore the accommodation ability of the human eye. For change of refractive power a lens shift is performed by an actuator. This paper reports on the first actuator solution for such an implant. It is based on a piezoelectric bender the displacement of which has to be amplified in a very limited design space to sufficiently drive the optics of an Artificial Accommodation System. This challenge is solved by a novel compliant mechanism realized in single-crystal silicon that additionally ensures the tilt-free translational displacement of the lens required for optical imaging quality. The design is free of any surface-friction to achieve high durability. Finite element analysis is conducted to calculate and optimize the performance of three linkage design variants. They were fabricated on a scale of 1.5:1 using deep reactive ion etching. Measurements were carried out to characterize the geometry, elastic behavior, and kinematic performance of the linkage samples. The results are in very good agreement with the calculations and indicate sufficient amplification of the piezoelectric bender''s displacement by the linkage to generate the required lens shift. [Copyright &y& Elsevier]

Abstract: A methodology developed for measuring Young’s modulus and the full stress–strain curve on micron-sized specimens was extended here to measure Poisson’s ratio. A dog-bone type specimen was used within a small loading machine with a maximum load of 5N. The specimen was fabricated from single crystal silicon (SC-Si) with the specimen gage and loading direction in the 〈001〉 orientation. A silicon on insulator (SOI) wafer was used with a deep reactive ion etching (DRIE) based process. Geometrical parameters of the initial cross-sectional area of the gage were measured by means of image processing on environmental scanning electron microscope (ESEM) images. The test setup also consists of an optical microscope with a monochromatic camera and a data acquisition system. The strains were obtained through the displacement field which was determined by means of digital image correlation (DIC). A speckle pattern was placed on the specimen gage. SC-Si was chosen to study since it is expected that on both the micro and macro-scales, Young’s modulus and Poisson’s ratio will have the same value. Hence, the accuracy of the method may be examined. The average value of Young’s modulus E =131.4±2.1GPa was obtained with the micro-specimens and is consistent with values determined on the macro-scale (E =130GPa). The average value of Poisson’s ratio on the micro-scale was found as ν =0.23±0.03 which is lower than the macro-scale value of ν =0.28. The failure stress was determined to be σ f =1.46±0.10GPa. Results for Young’s modulus reflect the reliability of the methodology which is suitable for characterization of a large variety of materials exploited in micro-devices for both sensing and actuation. The reasons for the low values measured for ν were investigated through emulations of determining the strains. An improvement in the image acquisition system is suggested. [Copyright &y& Elsevier]

Abstract: This paper presents 3-D MEMS-fabricated lithium rechargeable batteries relying on structured silicon rods as anodes in order to increase the effective electrode surface area. A new method of fabricating silicon micro/nano rod arrays with controllable diameters in the range of 300–8000nm is proposed. Different sizes of silicon rod-arrays as anodes were successfully incorporated into an all-solid-state battery construction. The structured architecture of the silicon electrodes allowed for a heightened surface area as well as improvement in cycle life and capacity over comparable planar electrodes. Structured rod array electrodes showed a first cycle coulombic efficiency over 80% which is more than double that of conventional powder composite silicon electrodes. Galvanostatic cycling of structured silicon rod electrodes showed highly reversible capacity for high current densities. Variation of rod diameter and current density revealed that decreasing the rod diameter leads to higher capacity and more stable cycling of batteries. [Copyright &y& Elsevier]

Abstract: A novel micromachined X-ray collector using anisotropically etched Si(111) side walls as X-ray mirrors for future astronomical missions is reported. The collector was designed to converge a 100mm parallel X-ray beam into a 4mm focus. In order to obtain smooth Si(111) side walls, dynashock-type ultrasonic waves were added during the anisotropic KOH etching. The surface roughness on the order of nm or less was achieved. The sidewalls or the X-ray mirrors were diced from the wafer as mirror chips and then adhered to a mount formed by deep reactive ion etching. The first light image was successfully obtained at Al K 1.49keV in a ISAS 30m-long X-ray beam line. [Copyright &y& Elsevier]

Abstract: In this paper, a novel design of silicon micro/nanopillars based multilayer water-cooled heat sink is presented, which enhances the overall thermal performance of electronics/MEMS components by a noteworthy amount. Heat dissipation rate of electronic devices is significantly increased by the silicon micro/nanopillars, which are grown in the microchannels by utilizing the micromasking effect in deep reactive ion etching. Due to the smaller diameter (0.5–2μm) and larger height (∼100μm), the surface area of these silicon pillars is very high, which results in enhanced convective heat transfer rate, and thus improved thermal performance. Gold thin films of varying thicknesses were used as etching mask during the fabrication of silicon microchannel and silicon nanopillars. Effects of etching mask type, mask thickness, platen power and substrate temperature on controlling the physical dimensions and the density of silicon pillars in the microchannels, are presented. A simple thermal model is developed to compare the heat dissipation characteristics of the heat sink, with and without the silicon pillars. The analytical analysis shows that the heat dissipation rate of the heat sink with silicon pillars can be increased by 16% than that of without silicon pillars. The effects of pillar diameter, height, and pillar density, on overall thermal resistance and the heat dissipation rate are also shown. [Copyright &y& Elsevier]

Abstract: A novel silicon condenser microphone with a rigid backplate has been proposed and fabricated. The backplate is fabricated on a separated wafer from the membrane to enhance acoustic characteristics, and they are combined together by gold–tin (Au/Sn) eutectic solder bonding. On a 2.5mm×2.5mm, 0.5μm thick low stress silicon nitride membrane, 2mm×2mm Au/Ni/Cr membrane electrode is deposited including 3μm thick Au/Sn layer. A 2mm×2mm, 150μm thick single crystal silicon rigid backplate has 1.8mm×1.8mm backplate electrode, and an air gap, which is fabricated by bulk micromachining, and a silicon deep reactive ion etching. Slots and 50–60μm radius circular acoustic holes to reduce air damping are also formed in the backplate chip. The fabricated microphone sensitivity is 39.8μVPa−1 (−88dB re. 1VPa−1) at 1kHz using 28V polarization voltage. The microphone shows flat frequency response within 1dB from 20Hz at least up to 5kHz. [Copyright &y& Elsevier]

Abstract: This work reports numerical and experimental investigations of capillary stop valves, which simply rely on the sudden expansion of a microchannel to control the liquid position. The simulation approach is based on the solution of the free surface equilibrium problem by the Finite Element Method. In contrast to analytical solutions, it deals rigorously with the complex geometries found in planar microfluidic systems. In contrast to energy minimization approach, it leaves the way open to the future introduction of dynamic effects. Microfluidic systems, including a new design of capillary stop valves expanding along both channel width and depth, have been fabricated by a two-level Deep Reactive Ion Etching technology. The silicon substrate is limited by a bonded PolyDimethlylSiloxane (PDMS) cover. The microvalves with cross-section dimensions down to 15μm×15μm, which are able to stop biological buffers and burst at pressures in the 1–10kPa range, are suitable for Lab-on-a-Chip applications. The computed burst pressure agrees well with the measurements when the liquid is water. However, when liquids containing surfactants are used a deviation is ascertained. It may be explained by the transient variation of surface tension due to the dynamics of meniscus expansion. [Copyright &y& Elsevier]

Deep reactive ion etching (DRIE) is employed to fabricate mechanically interlocking structures through which high-density fluidic interconnections are provided between microchannel-containing substrates. The geometric versatility that is achievable with DRIE facilitates the fabrication of high density interconnects of two types: (1) structures with mechanically interlocking “fins” used to align arbitrarily placed fluidic via holes and (2) interlocking hole and notched cylinder pairs that accomplish mechanical and fluidic interconnect in the same structure. Both types of interconnects are tested using silicon microfluidic circuit boards with off-chip coupling for flow control and measurement, and components that consist of simple channel arrays. The “fin” and notched cylinder/hole interconnects are tested up to pressures of 100 kPa and 70 kPa, respectively. [Copyright &y& Elsevier]

High-precision fabrication is indispensable for high-speed silicon micro-rotors for power MEMS applications so as to minimize the rotor imbalance that deteriorates the rotor performance. Etch variation of deep reactive ion etch (DRIE) process results in differences in rotor blade heights and thus rotor imbalance. A Fourier transform of the etch non-uniformity along the rotor circumference revealed the global etch variation across the wafer and local variations in etch rates depending on the concentration or proximity of the patterned geometry. Rotor imbalance arising from the global etch variation of DRIE process was estimated, which compared favorably to results obtained from spinning experiments. The global etch non-uniformity which culminates in rotor imbalance could be alleviated to 0.25% across a rotor of 4.2 mm diameter by optimizing the plasma chamber pressure. The developed DRIE recipe successfully reduced the rotor imbalance and thus enhanced the rotordynamic performance. The manufacturing processes presented herein are readily applicable to the constructions of other microstructures containing intricate geometries and large etched areas. [Copyright &y& Elsevier]