In this paper, we propose a new architecture for Capacitance-to-Digital convertor. We clarified the configuration that utilizes the time resolution of the frequency-Locked-Loop oscillator using a switched capacitor that enables stable operation, and integrated the circuit using 0.18µm standard CMOS technology. As a result, a power supply voltage of 1.2V, a capacitance resolution of 15aF, ENOB of 15.8bit, high resolution, and wide dynamic range conversion characteristics were achieved.
In this study, in an electret capacitor sensor (ECS), which is an electromechanical exchange device consisting of an electret sandwiched between two electrodes, ridges as spacers and grooves as gaps were formed in the PTFE layer of the insulating electrode by laser ablation. The ECSs were then fabricated using PTFE electrets, and the charge retention and airborne ultrasonic wave transmitting and receiving characteristics were investigated. The charge retention characteristics of the ECS with laser-patterned insulating electrodes were slightly lower than those of the silica-aggregate electret. as the thickness of the insulating layer increased or the groove width decreased, the transmitting and receiving sensitivity increased significantly and then peaked and degraded at the measurements of transmitting and receiving. The ECS with the highest peak sensitivity obtained by laser patterning had a bandwidth comparable to that of the conventional ECS with silica aggregate electret, but the peak sensitivity was improved by up to 8 dB. Therefore, laser patterning could contribute to the improvement of ECS performance.
This paper addresses semiconductor piezoresistive materials selection in MEMS engineering design. From the practical engineering point of view, it is important to understand piezoresistance properties of semiconductors even if less accuracy under feasibility design phase. However, piezoresistance is frequently analyzed based on first principle electronic band structure simulations by sophisticate physicists. Practical engineers not familiar with this simulation cannot directly apply useful information derived from the result of simulation. This paper provides practical prediction method for piezoresistance based on electronic band parameters obtained from the state-of-the-art solid-state physics. It is demonstrated that the crucial parameters which control the p-type shear piezoresistance coefficient π44 in diamond and zinc-blend single crystals are the inverse of square of bond length in unit cell atom, the square root of valence light hole mass, and the shear elastic compliance coefficient S44.
Surface-enhanced Raman scattering (SERS) is expected to be applied to real-time measurements in bioanalysis and environmental analysis because of its high sensitivity, label-free measurements, and suitability for long-term measurements. We are focusing on gold nanofève (GNF)-SERS structure deposited on a boehmite substrate because it is capable to have high-sensitivity and high-resolution measurements in a wide area. GNF-SERS-active patterns with improved adhesion by magnetron sputtering process were fabricated to integrate a microfluidic system. To evaluate the performance of the system, 4, 4'-Bypiridine (4bpy) was used for SERS measurement in the microchannel. This study shows that our microfluidic systems with the GNF-SERS active patterned area have the adequate potential for application and development in environmental analysis.
Functional textures with physical functions such as hydrophobicity are expected as a solution to improve the value of products. The purpose of this research was to achieve a femtosecond-pulsed laser processing method that can create hydrophobic micro-texture directly on a resin (polyethylene terephthalate) surface. A feedback control algorithm was proposed to achieve texture for improving the hydrophobicity. Pitch, tooth width, groove width, and depth were used as the geometric parameters of the micro-texture. Apparent contact angle of 144.9° was achieved with groove/tooth ratio of 9 when polyethylene terephthalate was processed with the hydrophobic micro-texture. We have achieved a processing speed that can process a 3 mm square area in 4 min. This laser processing technology will be realized as a low environmental impact, sustainable manufacturing that supports carbon neutrality and sustainability goals.
In this study, the electrical conductivity of a small sample of simulated plasma was measured by a microfluidic chip with electrodes. Saline samples of different concentrations were evaluated based on saline (0.9 w/v% NaCl solution). The electrical conductivity of samples of saline with albumin was also measured. In order to investigate whether the differences in conductivity were due to viscosity following Walden’s law, we correlated the electrical conductivity with the viscosity evaluated by the capillary method.
A simple method for predicting the nonlinear frequency response of the MEMS diaphragm with initial deformation is proposed in this study. The prediction consists of static analysis based on a finite-element-analysis and numerical analysis based on a normalized motion of equation. For piezoelectric micromachined ultrasonic transducers with different initial deformations (one flat and the other warped upward), their frequency responses are predicted. Typical hardening spring and mixed spring of hardening and softening are predicted for the flat and the upward-warped diaphragms, respectively. Since the trends of the predicted and experimental results are in good agreement, the proposed procedure is useful for the nonlinear frequency response.
A non-contact voltage sensing is one of the non-intrusive and galvanic methods for observing signal waveform. Frequency degradation due to the dielectric relaxation of PVC is a technical issue for the wideband (100 Hz ∼ 100 MHz) sensing. In this paper, reconstruction of the frequency response using Havriliak-Negami (HM) model is discussed.