This paper reports liquid-immersion inclined/rotated UV lithography for fabricating micro suction cups. Microstructures such as micro suction cups have been applied in various applications. However, the conventional fabrication method had limitations in suction force due to the insufficient inclination angle. We proposed liquid-immersion to inclined/rotated exposure (IRE), enabling greater microstructure inclination angles. IRE equipment was developed to fabricate PDMS micro suction cup arrays. The experimental inclination angle reached 51°, nearly doubling the conventional IRE method.
MEMS resonators were vacuum-encapsulated by Silicon Migration Seal (SMS) technology. SMS is new wafer-level vacuum packaging technology, which utilizes silicon reflow phenomena to close release holes in hydrogen (H2) environment at high temperature (>1000°C). In this study, we first demonstrated the encapsulation of a MEMS resonator made on an SOI wafer, which is one of the most standard structures for inertial sensors and timing devices. After the encapsulation, hydrogen trapped in the sealed cavity was diffused out by annealing at 430ºC in nitrogen (N2) environment for 27 hours. The resonator was capacitively driven and sensed, and the Q factor reached 6000. The sample after successful packaging was penetrated by focused ion beam (FIB) out of the resonating element area. Judging from the Q factor, the vacuum level of the sealed cavity is much better than that of the hydrogen annealing (10 kPa) and estimated ~60 Pa.
We have designed, fabricated, and tested a MEMS-based impedance biosensor for accurate and rapid detection of severe acute respiratory syndrome coronavirus 2 (SARS-COV-2) using of clinical samples. The device consists of focusing region that concentrate low quantities of the virus present in the samples to a detectable threshold, trap region hat maximize the captured virus, and detection region to detect the virus with high selectivity and sensitivity, using an array of interdigitated electrodes (IDE) coated with a specific antibody. Changes in the impedance value due to the binding of the SARS-COV-2 antigen to the antibody will indicate positive or negative result. The device was able to detect inactivated SARS-COV-2 antigen present in phosphate buffer saline (PBS) with a concentration as low as 50 TCID50/ml in 30 minutes. In addition, the biosensor was able to detect SARS-COV-2 in clinical samples (swabs) with a sensitivity of 84 TCID50/ml, also in 30 minutes.
This work demonstrated a novel dual-aptamer assay performed on a paper-based membrane composed of nitro-cellulose (NC) on an integrated microfluidic platform for detection of a biomarker, human neutrophil peptide 1 (HNP 1) for periprosthetic joint infection. A fully automated device involved a single loading process (< 5 min) for the newly developed sandwich assay for HNP 1 quantification. The primary aptamer was immobilized on NC membrane where HNP 1 was captured and detected using fluorescent-labelled secondary aptamer. The developed assay is faster (~ 30 min) and required less volume (only 50 μL) than traditional assays.
This paper reports a novel, cost-effective process for the fabrication of ultrathin silicon (Si) shuttles applied as insertion tools for highly flexible polyimide (PI) neural implants. The process exploits the so-called etching before grinding (EBG) process established to realize Si-based neural probes of the Michigan style. In this study, EBG is combined for the first time with a subsequent deep reactive ion etch (DRIE) process applied on the wafer-level. The innovative approach allows to realize insertion shuttles with a base thickness > 50 µm using wafer grinding and to reliably thin down the slender shuttle shanks (width ≥ 35 µm) to thicknesses as small as 15 µm using DRIE. The backgrinding liquid wax applied during wafer grinding enables the safe release of the delicate shuttle structures from their carrier wafer using isopropanol. Flexible, 15-µm-thin neural probes made from PI are precisely aligned and temporarily bonded to the custom-designed insertion shuttles applying polyethylene glycol (PEG) and reliably deployed into cortical tissue.
This paper reports on a 3D Hall sensor back-biased by rare-earth micromagnets which are integrated directly into the silicon substrate using a wafer-level fabrication process, called PowderMEMS. For the first time, the technique is used to realize a fully integrated back-biased magnetic field sensor. The feasibility of the approach is proven by measurements of the motion of a rotating gear wheel which represents a typical back bias application. Additionally, the ability of the approach to create optimal magnetic field geometries for magnetically biased sensors is demonstrated.
This work demonstrates a generic temperature compensation scheme applicable for nearly all types of resonators in CMOS-MEMS technology without additional process steps. Particularly, based on the arc-beam structure used for gap narrowing, specific geometrical design yields autonomous temperature dependent gap spacing between the tuning electrode and the resonator body and in turn results in electrical stiffness necessary for counteracting resonance frequency variation at varying temperatures. Using a clamped-clamped beam (CC-beam) resonator in the 0.35-µm CMOS-MEMS process platform as a demonstration vehicle, the compensation scheme reduces the first-order temperature coefficient (TCF 1 ) from -394.16 ppm/°C to +14.18 ppm/°C with a TCF 2 of -1.5757 ppm/°C 2 from 0 °C to 90 °C. With the help of the gap variation prediction model derived and knowledge of stress information, the arc-beam structure offers an elegant solution of temperature compensation for CMOS-MEMS resonators with inherent yet thermally induced stress.
Cochlear implants made of standard silicone electrode array (EA) are currently used to stimulate the auditory nerve of patients’ cochlea. The implants have a proximal diameter of 0.5mm and 2~3cm long composed of 20 bulk platinum electrodes and connection wires (Ø 25µm). Due to their stiffness and passive nature, the most difficult task during implant surgery is inserting the EA properly into the tympanic ramp of the patient's cochlea, often leading to trauma or incomplete insertion. In this work, we developed an original smart EA for efficient insertion. This prototype has a lower stiffness and functionalized with an electronic conducting polymer based micro-actuators able to bend under low electrical voltage stimulation. This prototype is expected to reduce the friction forces during insertion, allow better control of the insertion process, facilitate the work of the surgeon and decrease the probability of trauma.
An efficient simulation approach for obtaining the temperature-dependent thermoelastic damping (TED) quality factors of the mechanical modes in complex microelectromechanical systems (MEMS) gyroscopes is reported. It is shown that the temperature dependence of TED in an application-relevant temperature range can be obtained by a Taylor expansion of the full solution around room temperature. Our approach is much faster than performing the full simulation at every temperature. We find good agreement of our simulation results with measured data and show that TED is highly relevant for the overall quality factors of higher order modes.
This paper reports ion emission of an ionic liquid electrospray thrustor with two-stage electrodes made on glass substrate having through hole for low-cost micro/nano satellites. By using the two-stage electrodes, one for ion extraction and the other for acceleration, high and stable ion emission and propulsion force is obtained. The emitter array was fabricated on a silicon wafer and the electrodes were fabricated on both sides of a glass substrate. The ion emission test was conducted, and the emission current was observed successfully. Almost no ions were collected on the accelerator electrode and reached to the collector electrode, which demonstrates the advantage of the two-stage configuration.
Metal oxides nanowires and novel heterostructures are synthesized using different techniques and finally integrated into gas sensing platform. In particular, nanowires were synthesized using thermal oxidation and VLS mechanism. While, heterostructures i.e. NiO/ZnO (p-n) and NiO/NiWO 4 /WO 3 (p-p-n) were synthesized using VLS and VS mechanisms. Detailed investigations reveal the dependence of sensors selectivity and sensitivity on nanowires synthesis techniques. While, the superior performance of heterostructures as compared to bare nanowires presents the novel pathway to further enhance the performance of nanostructured gas sensors.
This paper presents high-inductance-density MEMS 3D-solenoid magnetic core transformers that are wafer-level fabricated by a novel thick-metal micro-casting technique. With the embedded thin-film high-permeability ferrite core, an over 7 times boost in inductance (from 43.3 nH to 334.2 nH) and 25% increment in coupling coefficient (from 0.76 to 0.96) are achieved. For the batch-fabricated transformer in a tiny footprint of 6 mm 2 , an over 1.6 A saturated current and one of the best-reported power transfer efficiency of 89.5% at a lower frequency of 10 MHz are demonstrated. The proposed magnetic core transformers are ideal for high-efficiency integrated DC-DC power conversion applications.
This paper reports the field emission (FE) properties of a novel array of diamond nanowires (DNWs). The DNWs structure was prepared by annealing the nano-crystalline diamond (NCD) films obtained by MPCVD in air, and the surface hydrogenation was realized by using hydrogen plasma. A flat anode was fabricated by micromachining, and assembled respectively with NCD film and nanowire cathodes to achieve a FE test structure with a gap of 1.03 μm. The FE properties of NCD films and DNWs were tested under a vacuum of 2.6×10 -4 Pa. The results show that the FE current density of the DNWs array is as high as 174 mA/cm 2 and the turn-on field is as low as 2.3 V/μm, which is significantly better than that of the NCD film.
Vasculogenesis, the formation of de novo blood vessels, occurs in several fundamental physiological and pathological processes, including embryonic development, adult angioblast mobilization, and tumor development. Although substantial research has been performed on vasculogenesis, a comprehensive understanding of the morphological changes during the developmental process of vasculature remains elusive. Here, we report a deep learning-based visual methodology in conjugation with a vasculature-on-a-chip model that can recognize and classify the developmental phases of an on-chip vascular network. Combining the unsupervised and supervised learning strategies, three distinct time-dependent morphological phases during vasculogenesis were identified. The temporal variation trajectory of vascular morphology during entire vascularization process was revealed.
This paper reports a novel flexible fractal microelectrode integrated with the catheter to achieve diagnosis and treatment for low-voltage pulsed field ablation (PFA). The fractal design increases the ratio of the edge length to the geometric surface area of the electrode, which contributes to the transfer of current from the electrode into the tissue. Besides, the fractal structure reduces the spacing between the electrodes, which can obtain a large electric field. Pt-Black coating enhances the electrical stimulation and electrocardiogram (ECG) recording capability. Foremost, it achieves in vivo ablation at 100 V on rat hearts. In short, the device can perform ablation procedures independently, including low-voltage PFA and ECG recording.
We report a method of REWOD energy harvesting using a bumpy formation of gallium coated (~20 nm) electrode as a nonwetting surface and utilizes naturally formed oxide shell of gallium (~3 nm) as a dielectric layer, while using naturally oxidized Galinstan as a conductive liquid. Compared with Cytop and Parylene-C coated flat electrodes, all liquid metal based energy harvester was able to generate continuous power without wetting on the surface. Maximum power generation of 268 μW was achieved when the gap between two electrodes was 4.5 mm, 7 V pp and 65 Hz applied to a woofer.
Two thoroughly integrated sensor node interfaces for the storage of mechanical and electrical measures are demonstrated. For long-time monitoring tasks, the continuous accessibility of electrical auxiliary energy is often critical, as the sensing device has to be on standby, even if the measures of interest - extremal values, integrals or total numbers of events - are retrospectively of interest, only. Novel mechanical or nanoionic interfaces allow storing these measures by using the inherently available energy from the measures. Any kind of acceleration, force or pressure provides sufficient mechanical energy to extract and store quantitative results in a mechanical MEMS storage whereas electrical energy, e.g. from piezo sensors or photoelectric elements can be stored in a nanoionic memory. Interfaces for both concepts exemplified for inertial sensors are described and demonstrated here.
This study presents a novel piezoelectric MEMS microspeaker consisted of the cantilever-plate actuator, central-diaphragm, and connecting meandering-springs. Features of the design: (1) cantilever-plate actuator: supply large actuation force with simple electrical routing, (2) central-diaphragm: simple Si layer structure to provide relatively flat piston motion, (3) connecting meandering-spring: transmit actuation force to central-diaphragm and reduce the influence of thin film residual stresses. Thus, large average central-diaphragm out-of-plane displacement is achieved, and the piston mode of microspeaker excited by cantilever-plate actuators could ensure good THD (Total-Harmonic-Distortion i.e. high fidelity) response. Measurements show the design has a maximum SPL (Sound-Pressure-Level) of 123 dB and full-range (20 Hz~20 kHz) 80dB bandwidth with overall THD below 7 % under 0.707 Vrms+10 VDC driving voltage in standard ear simulator.
We compared two on-chip glomerular filtration barrier models using immortalized podocytes and kidney organoid-derived podocytes from induced pluripotent stem cells (iPSCs). Podocytes and human umbilical vein endothelial cells (HUVECs) were seeded on the side wall of fibrin gel in a three-channel polydimethylsiloxane (PDMS) device. Both models showed higher filtration rate for inulin than albumin, and significantly higher selectivity was measured when organoid-derived podocytes were used. This study demonstrated the importance of using highly functional podocytes derived from iPSC organoids than conventional immortalized podocytes. The results will be the basis for the creation of glomerular chips that can mimic more biological functions in the future.
