Electrical impedance distribution reconstruction was examined based on ultrasonic B-mode imaging with a three-layered breast model by a multisensing probe. In the probe, 16 electrodes arrayed on a thin film are pasted on the surface of the ultrasonic probe. The electrical voltages are measured by several combinations of the 16 electrodes. In addition, an ultrasonic B-mode image is simultaneously obtained using the probe. The electrical impedance distribution is reconstructed by using the B-mode image as the prior information. Therefore, the probe makes both the electrical conductivity and ultrasonic B-mode images possible. In the experiment, a three-layered breast model and multisensing system were developed, and the conductivity distribution and B-mode images of the model were obtained. The results indicate that estimation of the tumor position in the breast model is possible using the developed system, even though there are some problems, such as the stability of the model and the measurement accuracy of the system.

This paper describes a design integration method that simulates the sensing characteristics of a low-input-impedance sensing circuit combined with a sensor having a complexly structured vibration amplification mechanism (VAM). The sensing circuit that detects vibrations with zero power transforms acceleration to an electrical signal by transferring charges by utilizing the kinetic energy of the movable element in the sensor. The VAM adjusts the resonance frequency to within the target range of the vibration spectrum to obtain a sufficient signal intensity. For the circuit evaluation, a vibration sensor needs to be connected to a test chip because the input impedance is set low to improve charge transfer efficiency and the voltage signal generated by the charge transfer is affected by the vibration waveform. In addition, the VAM has a complex structure that is not regarded as a single rigid body, making it difficult to estimate the sensing performance. The proposed method solves this problem by simplifying the VAM simulation model using two parameters of the spring elements and extracting the parameters from a measured data point based on an independent relationship between the parameters. A test chip fabricated by using the 0.35-µm CMOS process detects a vibration at 40 Hz and 0.4 g with 0.7 nW, and the validity of the proposed method is confirmed via the consistency between the simulated results obtained based on the extracted parameters and the entire set of measured data. The design integration makes it possible to design sensing circuits that need the complex-structured sensor to be connected for evaluation.

Enzyme screening is an essential requirement in various fields. Electrochemical measurements have various advantages such as quick response and inexpensive measurement; however, the number of wires of the array electrode increase with the number of measurements. To solve this problem, we have developed the light addressable amperometric sensor (LAAS). This study demonstrates the performance of this two-dimensional electrochemical array sensor. LAAS with a back surface electric field (BSF), which increases the number of photoexcited carriers, and LAAS without BSF were prepared. The formation of the diode in the device was confirmed by measurement of the I-V characteristics. The resolution was calculated by comparing the two-dimensional images obtained by the measurement of the prepared solution. Finally, the concentration dependence of the ferricyanide ion/ferrocyanide ion was measured, with detection limits of 270 µM for LAAS without BSF and 17 µM for LAAS with BSF. LAAS has the potential to be applied to high-throughput screening using enzymes.

This paper reports on pH-sensitive thin films of sputter-deposited TiO₂ on indium tin oxide electrodes for biosensor applications. The composition and crystallographic properties of the TiO₂ thin films were controlled by varying the substrate temperature and total pressure used for sputtering. The pH sensitivity and potential drift of TiO₂ thin films with different ratios of anatase to rutile phases were compared. It was found that the TiO₂ films with a predominant rutile phase exhibited low drift characteristics and those with a predominant anatase phase exhibited high sensitivity and lower hysteresis. Furthermore, lactate sensing using lactate dehydrogenase immobilized on TiO₂ thin films was demonstrated.

A new multilayered sensor that allows simultaneous measurement of electromyography (EMG), mechanomyography (MMG), and near-infrared spectroscopy (NIRS) signals is developed for a more detailed analysis of muscular activity. The proposed sensor is a layered structure of a thin film with an indium tin oxide (ITO) electrode, a polyvinylidene fluoride (PVDF) film with ITO electrodes, and optical sensors. EMG, MMG, and NIRS signals, which provide three types of information, are measured using the ITO electrodes, PVDF film, and optical sensors. The three types of data obtained enable muscular activity to be evaluated in more detail. In an experiment, a simultaneous measurement of EMG, MMG, and NIRS signals at the isometric ramp contraction of the forearm is demonstrated. The layered sensor demonstrates potential for a more detailed muscular analysis.

Here, we report an electrochemical biosensing system capable of performing daily self-testing of uric acid (UA) using saliva. With the aim of daily use, we employed a simplified paper-based sampling device that allows users to collect saliva by themselves, and an amperometric biosensor for the rapid determination of salivary uric acid (SUA) contained in the sampling device without any pretreatment. To utilize the biosensor on site, a wireless control unit with an on-chip potentiostat and Zigbee wireless module was developed. The fundamental characteristics of the biosensor were first evaluated using amperometric techniques. A linear relationship between the concentrations of UA and output currents was confirmed to range from 10 µM to 400 µM. As a real sample test, the biosensor was applied to the measurement of SUA levels in seven healthy male volunteers. The estimated SUA levels were similar to those measured using a commercial UA test kit. Changes in the SUA levels after exercise were also tested. The SUA levels in all the volunteers increased after a bicycle exercise (140 bpm, 10 min). This result was consistent with those obtained in previous studies. Based on the obtained results, our sensor is expected to be useful in the daily self-testing of SUA to improve public health.

An impedancemetric thick-film CO sensor using RE₂CuO₄ (RE = La, Sm, Eu, Gd) oxides was examined for monitoring carbon monoxide. The thick-film sensor using Eu₂CuO₄ showed a high response to CO. The response was almost linear to CO concentration between 50 and 600 ppm, and the 90% response time to 300-ppm CO was approximately 90 s, although the CO response of the sensor was affected by NO and NO₂ at low concentration.