Design and analysis for the SPICE parameters of waveform-selective metasurfaces varying with the incident pulse width at a constant oscillation frequency.

In this study, we numerically demonstrate how the response of recently reported circuit-based metasurfaces is characterized by their circuit parameters. These metasurfaces, which include a set of four diodes as a full wave rectifier, are capable of sensing different waves even at the same frequency in response to the incident waveform, or more specifically the pulse width. This study reveals the relationship between the electromagnetic response of such waveform-selective metasurfaces and the SPICE parameters of the diodes used. In particular, we draw conclusions about how the SPICE parameters are related to (1) the high-frequency operation, (2) input power requirement and (3) dynamic range of waveform-selective metasurfaces with supporting simulation results. First, we show that reducing a parasitic capacitive component of the diodes is important for realization of the waveform-selective metasurfaces in a higher frequency regime. Second, we report that the operating power level is closely related to the saturation current and the breakdown voltage of the diodes. Moreover, the operating power range is found to be broadened by introducing an additional resistor into the inside of the diode bridge. Our study is expected to provide design guidelines for circuit-based waveform-selective metasurfaces to select/fabricate optimal diodes and enhance the waveform-selective performance at the target frequency and power level. Our results are usefully exploited to ensure the selectivity based on the pulse duration of the incident wave in a range of potential applications including electromagnetic interference, wireless power transfer, antenna design, wireless communications, and sensing.

Design of a Self-Controlled Dual-Oscillator-Based Supply Voltage Monitor for Biofuel-Cell-Combined Biosensing Systems in 65-nm CMOS and 55-nm DDC CMOS.

A supply voltage monitor (SVM) with self-controlled dual-oscillator-based architecture is proposed herein for biosensing systems combined with a biofuel cell (BFC) in this paper. The output of the BFCs can be used to monitor the biological signals while powering the BFC-combined biosensing systems. Thus, the SVM is designed to convert the change in the supply voltage (V DD) into a code. The architecture of the proposed SVM allows self-controlled periodic operation without external signals. Furthermore, the frequency subtraction technique that uses two oscillators employing gate-leakage-based architecture with different frequency sensitivities to V DD allows accurate code generation with low power consumption and a small circuit area for supply voltage monitoring. The proposed SVM is fabricated using two different CMOS process technologies, including 65-nm CMOS and 55-nm deeply depleted channel (DDC) CMOS. The implementation of the 65-nm CMOS obtains an operating V DD range of 250 mV (0.75-1 V), draws a standby power consumption of 1.4 nW at 0.75-V V DD, exhibits a resolution of 2.4 mV with a nonlinearity error of -8.4/ +12.1 mV, and occupies a circuit area of 0.0047 mm2. Meanwhile, the implementation of the 55-nm DDC CMOS for low-voltage operation achieves an operating V DD range of 300 mV (0.225-0.525 V), draws a standby power consumption of 32.5 nW at 0.25-V V DD, exhibits a resolution of 0.94 mV with a nonlinearity error of -15.2/ +14 mV, and occupies a circuit area of 0.0032 mm2.

A 65-nm CMOS Fully Integrated Analysis Platform Using an On-Chip Vector Network Analyzer and a Transmission-Line-Based Detection Window for Analyzing Circulating Tumor Cell and Exosome.

A fully integrated CMOS circuit based on a vector network analyzer and a transmission-line-based detection window for circulating tumor cell (CTC) and exosome analysis is presented for the first time. We have introduced a fully integrated architecture, which eliminates the undesired parasitic components and enables high-sensitivity, to analyze extremely low-concentration CTC in blood. The detection window was designed on the high-sensitive coplanar waveguide line. To validate the operation of the proposed system, a test chip was fabricated using 65-nm CMOS technology. Measurements were performed after adding a tiny lump of silicone or a droplet of water on its detection window. The measured results show |S_21| degradation of -1.96 dB and -6.04 dB for the silicone and the droplet, respectively, at 1.4 GHz. In addition, in another measurement using magnetic beads, it is confirmed that the proposed circuit can analyze even low concentrations of 20 beads/µL. As well as microbeads, measurement with CTCs was successfully demonstrated.

Design and Experimental Verification of a 0.19 V 53 µW 65 nm CMOS Integrated Supply-Sensing Sensor With a Supply-Insensitive Temperature Sensor and an Inductive-Coupling Transmitter for a Self-Powered Bio-sensing System Using a Biofuel Cell.

In this paper, we present a self-powered bio-sensing system with the capability of proximity inductive-coupling communication for supply sensing and temperature monitoring. The proposed bio-sensing system includes a biofuel cell as a power source and a sensing frontend that is associated with the CMOS integrated supply-sensing sensor. The sensor consists of a digital-based gate leakage timer, a supply-insensitive time-domain temperature sensor, and a current-driven inductive-coupling transmitter and achieves low-voltage operation. The timer converts the output voltage from a biofuel cell to frequency. The temperature sensor provides a pulse width modulation (PWM) output that is not dependent on the supply voltage, and the associated inductive-coupling transmitter enables proximity communication. A test chip was fabricated in 65 nm CMOS technology and consumed 53 µW with a supply voltage of 190 mV. The low-voltage-friendly design satisfied the performance targets of each integrated sensor without any trimming. The chips allowed us to successfully demonstrate proximity communication with an asynchronous receiver, and the measurement results show the potential for self-powered operation using biofuel cells. The analysis and experimental verification of the system confirmed their robustness.

Development of Microelectrode Arrays Using Electroless Plating for CMOS-Based Direct Counting of Bacterial and HeLa Cells.

The development of two new types of high-density, electroless plated microelectrode arrays for CMOS-based high-sensitivity direct bacteria and HeLa cell counting are presented. For emerging high-sensitivity direct pathogen counting, two technical challenges must be addressed. One is the formation of a bacteria-sized microelectrode, and the other is the development of a high-sensitivity and high-speed amperometry circuit. The requirement for microelectrode formation is that the gold microelectrodes are required to be as small as the target cell. By improving a self-aligned electroless plating technique, the dimensions of the microelectrodes on a CMOS sensor chip in this work were successfully reduced to 1.2 µm × 2.05 µm. This is 1/20th of the smallest size reported in the literature. Since a bacteria-sized microelectrode has a severe limitation on the current flow, the amperometry circuit has to have a high sensitivity and high speed with low noise. In this work, a current buffer was inserted to mitigate the potential fluctuation. Three test chips were fabricated using a 0.6- µm CMOS process: two with 1.2 µm × 2.05 µm (1024 × 1024 and 4 × 4) sensor arrays and one with 6- µm square (16 × 16) sensor arrays; and the microelectrodes were formed on them using electroless plating. The uniformity among the 1024 × 1024 electrodes arranged with a pitch of 3.6 µm × 4.45 µm was optically verified. For improving sensitivity, the trenches on each microelectrode were developed and verified optically and electrochemically for the first time. Higher sensitivity can be achieved by introducing a trench structure than by using a conventional microelectrode formed by contact photolithography. Cyclic voltammetry (CV) measurements obtained using the 1.2 µm × 2.05 µm 4 × 4 and 6- µm square 16 × 16 sensor array with electroless-plated microelectrodes successfully demonstrated direct counting of the bacteria-sized microbeads and HeLa cells.