This paper reports upon a new process for the flow sensor fabrication of a thermal microelectromechanical systems (MEMS) and its performance improvement. A unique feature of the proposed process is the silicon etching, which is a combination of normal crystal-oriented silicon etching and isotropic etching of polycrystalline silicon (poly-Si). The poly-Si layer works as a sacrificial layer and promotes etching of the silicon substrate in the horizonal direction, thereby enabling location of the etching holes in the membrane of the flow sensor without the conventional etching rules. Some designs for the flow sensors, which have been infeasible with normal processes, were thus fabricated and evaluated. Hence, the new process improves the design flexibility of the membrane and enhances flow sensor performance, such as 38.3% reduction in power consumption.

We developed a novel technique for measuring neuronal extracellular potentials in a neuron-astrocyte co-culture system using a SiN (silicon nitride) membrane having microelectrodes and microholes. An 8×8 microelectrode array was formed on one side of a 1 µm-thick SiN membrane, and multiple microholes of 5 µm in diameter were opened through the membrane. Then, neurons were cultured on the microelectrodes after astrocytes were cultured on the back side of the membrane. The neuronal spikes measured in this novel back-to-back co-culture method were compared with those in the conventional method in which both of neurons and astrocytes were co-cultured on the microelectrodes. In the conventional method, formation and enlargement of cellular aggregates made neurons out of touch with microelectrodes, and posed measurement of a small number of spikes. On the other hand, our novel method permitted the firm contact between neurons and microelectrodes and the cell-to-cell interaction through microholes, and therefore neuronal spikes increased drastically with culture time, which led to stable measurement of neuronal extracellular potentials.

This paper presents a method for accelerating photo-induced wettability conversion on TiO₂ thin films by combination of ultraviolet (UV) light irradiation and electrically polarization. We focused on the behavior of photogenerated holes in wettability conversion. The amount of hole at the vicinity of TiO₂ surface was attempted to increase by electrical polarization in order to assist wettability conversion. Acceleration of hydrophobilization was successfully demonstrated under dark by positive self-bias electric field in TiO₂ thin films which was induced by Pt/TiO₂ Schottky junction, and hydrophilization was also accelerated by negative bias electric field in TiO₂ thin films which was applied by Se/TiO₂ photovoltaic cells under light irradiation.

This paper presents an energy harvesting technique that generates effective DC power from non-stationary weak environmental vibrations. We employ a voltage-boost rectifier (VBR) circuit utilizing small output from a vibrational energy harvester under non-stationary vibrations, which cannot be utilized by conventional rectifiers. A VBR circuit is fabricated by the complementary metal-oxide-semiconductor (CMOS) technology and packaged as a chip. The VBR chip is combined with an electret-based MEMS vibrational energy harvester and experimentally evaluated under non-stationary vibration. Measurement results show that the proposed system can deliver an effective DC voltage over 5.6 V from non-stationary vibrations (0.3 m/s²_RMS) while a conventional diode rectifier delivered 0.3 V or lower.

Nucleic amplification tests (NATs) are sensitive and specific methods to diagnose infectious diseases. Real-time polymerase chain reaction (PCR) is the gold standard, but it requires expensive apparatus and regents because of fluorescent detection. This study performed a combination of a conventional PCR and microbeads dielectrophoresis (DEP)-based DNA detection method to detect the SARS-CoV-2 gene quantitatively. SARS-CoV-2 is a virus causing COVID-19 and has caused the pandemic worldwide. In the microbeads DEP-based DNA detection method, the amplified DNA, amplicon, is attached to microbeads, the amplicon-labeled microbeads are detected by dielectrophoretic impedance measurement. As a result, the technique demonstrated that same sensitivity as that of real-time PCR. Our method enables the cheap diagnosis of infectious disease instead of expensive real-time PCR.

Trans-epithelial electrical resistance (TEER) is a widely used as an experimental readout and a quality control assay for measuring the integrity of epithelial monolayers. However, it is difficult to compare TEER values among different Organ-on-a-Chip (OoC) devices due to considerable errors in measurements. Here we report an OoC design method focusing on the electrodes that achieves the accurate measurement of TEER values. This approach has employed an index of “sensitivity variation” calculated from current density depending on electrodes configuration and structure of cell culture chamber, allowing to identify the suitable electrodes design for TEER measurements. The validity of this approach was successfully confirmed to measure TEER by impedance spectroscopy measurements and detect changes in integrity of Caco-2 cell. The present approach will allow a comparison of TEER values across any OoC as well as real-time assessment of biological functions.

A MEMS vibrational energy harvester is developed as a power source for infrastructures monitoring systems. The output power is maximized by appropriately choosing the load resistance in accordance with the vibration conditions of the vibration source. Output power of more than 500 µW is obtained from the vibrations caused by a vacuum pump used in a factory.

We propose a triboelectric nanogenerator with pyramidal microstructure array fabricated by 3D lithography at contact interface. Since the actual contact area of the periodic pyramidal structure is relatively easy to predict, we evaluated the relationship between the size of the pyramidal microstructure at the contact interface and the power generation performance in a vertical contact-separation mode.

This paper describes the fabrication of a tactile display with a shape memory alloy (SMA) thick film actuator array bonded to an Si substrate using through-substrate-via (TSV) electrodes and diode elements to realize individual connection without reverse current flow. The SMA actuator array (5×5 array, 2 mm pitch) was fabricated from a flash-evaporated SMA thick film while the TSV substrate was fabricated using a different Si substrate. After large through holes and cavities were etched for the vibrating SMA actuator, the TSV electrodes were formed by double-side sputtering and lift-off processes. The fabricated diode element exhibited a sufficient backward breakdown voltage above 36 V and low forward resistance of 15 Ω. On the fabricated SMA and TSV substrates with through holes, 10-µm and 5-µm-thick SU-8 patterns were uniformly formed, respectively, and then, the substrates were bonded using the patterned SU-8 layers with a bonding strength above 3.5 MPa. Simultaneously, in the bonding process, the electrodes on the SMA and TSV substrates were electrically connected via an Ag paste dispensed in the opening of the SU-8 pattern. Using the proposed processes, we successfully completed the tactile display mechanism with the arrayed SMA actuator , including the TSV substrate with diode elements.

The power-saving infrared sensor is attractive for detecting human and environment. A new infrared sensor is fabricated using the electrostatic torsional resonator enabling the electrical measurement. Compared to the previous experiments using the laser Doppler measurement, the possibility for the compact sensor is confirmed.