Conventional High Intensity Focused Ultrasound (HIFU) is a therapeutic modality which is extracorporeally administered. In applications where a relatively small HIFU lesion is required, an intravascular HIFU probe can be deployed to the ablation site. In this paper, we demonstrate the design and implementation a fully integrated HIFU drive system on a chip to be placed on a 6 Fr catheter probe. An 8-element capacitive micromachined ultrasound transducer (CMUT) ring array of 2 mm diameter has been used as the ultrasound source. The driver chip is fabricated in 0.35 μm AMS high-voltage CMOS technology and comprises eight continuous-wave (CW) high-voltage CMUT drivers (10.9 ns and 9.4 ns rise and fall times at 20 V _pp output into a 15 pF), an eight-channel digital beamformer (8-12 MHz output frequency with 11.25° phase accuracy) and a phase locked loop with an integrated VCO as a tunable clock source (128-192 MHz). The chip occupies 1.85 × 1.8 mm ² area including input and output (I/O) pads. When the transducer array is immersed in sunflower oil and driven by the IC with eight 20 V _pp CW pulses at 10 MHz, real-time thermal images of the HIFU beam indicate that the focal temperature rises by 16.8 °C in 11 seconds. Each HV driver consumes around 67 mW of power when driving the CMUT array at 10 MHz, which adds up to 560 mW for the whole chip. FEM based analysis reveals that the outer surface temperature of the catheter is expected to remain below the 42 °C tissue damage limit during therapy.

This paper presents a new fully integrated CMOS capacitance sensor chip with a wider input dynamic range (IDR) compared to the state-of-the-art, suitable for a variety of life science applications. With the novel differential capacitance to current conversion topology, it achieves an IDR of about seven times higher compared to the previous charge based capacitive measurement (CBCM) circuits and about three times higher compared to the CBCM with cascode current mirrors. It also features a calibration circuitry consisting of an array of switched capacitors, interdigitated electrodes (IDEs) realized on the topmost metal layer, a current-controlled 300 MHz oscillator, and a counter-serializer to create digital output. The proposed sensor, fabricated in AMS 0.35 μm CMOS technology, enables a high-resolution measurement, equal to 416 aF, of physiochemical changes in the IDE with up to 1.27 pF input offset adjustment range (IOAR). With a measurement speed of 15 μs, this sensor is among the fast CMOS capacitive sensors in the literature. In this paper, we demonstrate its functionality and applicability and present the experimental results for monitoring 2 μL evaporating droplets of chemical solvents. By using samples of solvents with different conductivity and relative permittivity, a wide range of capacitance and resistance variations in the sample-IDE interface electric equivalent model can be created. In addition, the evaporating droplet test has inherently fast dynamic changes. Based on the results, our proposed device addresses the challenge of detecting small capacitance changes despite large parasitic elements caused by the ions in the solution or by remnants deposited on the electrode.

CMOS capacitive sensors reported for high accuracy cellular molecular measurements typically suffer from significant parasitic capacitance changes caused by remnants and sediments during the experiment with several biological and chemical reactions. In this paper, we propose a novel calibration-free capacitive sensing system that addresses this problem. The proposed CMOS capacitive sensor includes interdigitated electrodes (IDEs), a capacitance-to-current converter with a wide input dynamic range (IDR), a variable reference capacitor, and an oscillator-based analog-to-digital converter (ADC) which has been fabricated using 0.35 μm AMS CMOS process. Sweeping the value of the variable reference capacitor from 0.1 fF up to 1.27 pF with a step of 10 fF and repeating the sweep each second during the experiment allows the creation of time-resolved three-dimensional (3D) fingerprints for the measurement of capacitance variations of the sample-electrode interface resulted from both the target material as well as non-target parasitic capacitances. We have tested the sensor using three different chemical solvents. The four different categories of curves that constitute the fingerprints of the chemicals showed a match with the post-layout simulation results. Capacitance change in the range of 0.416 fF up to 1.27 pF can practically be monitored. The electrode area of 110 μm by 220 μm and the micrometer chamber size allows for placing tiny droplets of a few microliters. The generated fingerprint is valid for the chemicals with a conductivity of up to 5 mS/cm.

This article presents a new wafer-bonding fabrication technique for Capacitive Micromachined Ultrasonic Transducers (CMUTs) using polymethyl methacrylate (PMMA). The PMMA-based single-mask and single-dry-etch step-bonding device is much simpler, and reduces process steps and cost as compared to other wafer-bonding methods and sacrificial-layer processes. A low-temperature (< $180{}^{\circ }\mathrm{C}$ ) bonding process was carried out in a purpose-built bonding tool to minimize the involvement of expensive laboratory equipment. A single-element CMUT comprising 16 cells of 2.5 $\mathrm{mm}$ radius and 800 $\mathrm{nm}$ cavity was fabricated. The center frequency of the device was set to 200 kHz for underwater communication purposes. Characterization of the device was carried out in immersion, and results were subsequently validated with data from Finite Element Analysis (FEA). Results show the feasibility of the fabricated CMUTs as receivers for underwater applications.

This paper presents a novel multimodal CMOS based biosensor consisting of integrated capacitive and thermal sensors for Lab-on-Chip applications. A new capacitive sensor is also proposed which converts the capacitance changes to frequency by using a current-controlled oscillator. This sensor works based on charge based capacitance measurement (CBCM) technique. Its operation in current mode helps this capacitive sensor to have a relatively wide dynamic range along with a suitable resolution. We also put forward the analysis of sensing and parasitic capacitances using a 3D field solver incorporated with Cadence software. Based on these results, the proposed multi-sensor system offers advantages for high-throughput cellular monitoring purposes.

This paper presents the design, and implementation of a new CMOS capacitive sensor and proposes the applicability of the sensor in monitoring the dried DNA mass for the emerging DNA memory technologies. The concept of DNA-based data storage has shown to be a promising solution with an ultra-high data density storage capability of gigabytes per nanogram mass of DNA. There are several drawbacks in achieving a ubiquitous technology and existing research has mostly addressed the translation of digital data to synthesized nucleotides, the physical storage of DNA, and reading out the data via sequencing, as well as computational processes. In this paper, we tackle the challenge of monitoring the physical storage of dried DNA material by developing a CMOS capacitive sensor that detects the dried DNA mass and inherits the highly integrable nature of CMOS chips with other parts to develop a DNA storage system. The successful detection of down to 45 ng $/ \boldsymbol {\mu }\text{L}$ mass of dried DNA has been successfully shown with the experimental results that consist of five runs for five different concentrations. Based on the results, the detection range of sub-pico Mol has been achieved which is compatible with the concentrations of DNA used in DNA memory technologies.