Saoni Banerji

Textile-based wearable robotics increasingly integrates sensing and energy materials to enhance functionality, particularly in physiological monitoring, demanding higher-performing and abundant robotic textiles. Among the alternatives, activated carbon cloth stands out due to its monolithic nature and high specific surface area, enabling uninterrupted electron transfer and energy storage capability in the electrical double layer, respectively. Yet, the potential of monolithic activated carbon cloth electrodes (MACCEs) in wearables still needs to be explored, particularly in sensing and energy storage. MACCE conductance increased by 29% when saturated with Na₂SO₄ aqueous electrolyte and charged from 0 to 0.375 V. MACCE was validated for measuring pressure up to 28 kPa at all assessed charge levels. Electrode sensitivity to compression decreased by 30% at the highest potential due to repulsive forces between like charges in electrical double layers at the MACCE surface, counteracting compression. MACCE’s controllable sensitivity decrease can be beneficial for garments in avoiding irrelevant signals and focusing on essential health changes. A MACCE charge-dependent sensitivity provides a method for assessing local electrode charge. Our study highlights controlled charging and electrolyte interactions in MACCE for multifunctional roles, including energy transmission and pressure detection, in smart wearables.

This paper presents a linear electrochemomechanical model for microscale ionic actuators. A frequency-domain approach is used to facilitate model interpretation, simplify model application, and accelerate the generation of actuator-specific models. A system comprising a micro PEDOT:PSS/PEO actuator with external loading at its tip was modeled to incorporate the mass loading effect using the proposed approach. Analysis showed that the simulation results of the reported model were in agreement with the experimental measurements conducted with variability in the mass and input voltage. The success of the proposed modeling approach promises to enable its application in the control of microscale ionic actuators for potential biomedical applications. [2020-0388]

This work presents the design and characterization of a resonant CMOS-MEMS pressure sensor manufactured in a standard 180 nm CMOS industry-compatible technology. The device consists of aluminum square plates attached together by means of tungsten vias integrated into the back end of line (BEOL) of the CMOS process. Three prototypes were designed and the structural characteristics were varied, particularly mass and thickness, which are directly related to the resonance frequency, quality factor, and pressure; while the same geometry at the frontal level, as well as the air gap, were maintained to allow structural comparative analysis of the structures. The devices were released through an isotropic wet etching step performed in-house after the CMOS die manufacturing, and characterized in terms of Q-factor vs. pressure, resonant frequency, and drift vs. temperature and biasing voltage.

This paper presents a behavioral modeling technique for CMOS-MEMS microresonators that enables simulation of a MEMS resonator model in Analog Hardware Description Language (AHDL) format within a system-level circuit simulation. A 100 kHz CMOS-MEMS resonant pressure sensor has been modeled into Verilog-A code and successfully simulated within Cadence framework. Analysis has shown that simulation results of the reported model are in agreement with the device characterization results. As an application of the proposed methodology, simulation and results of the model together with an integrated monolithic low-noise amplifier is exemplified for detecting the position change of the resonator.

Comprehensive characterization results of CMOS-microelectromechanical systems resonant pressure sensor are presented. We have extensively evaluated the key performance parameters of our device in terms of quality factor (Q) variations under variable conditions of temperature and pressure, characterized by Knudsen number (K _n ). The fundamental frequency of the reported device is 104.3 kHz. Over the full-scale pressure range of 0.1 to 100 kPa and a temperature range of -10 °C to 85 °C, Q from 450 to 62.6 have been obtained. Besides, static variations of the device capacitance have been measured and analyzed with temperature to evaluate the spring softening and the pull-in effects. A nonlinearity analysis has been performed to assess the device stability. Furthermore, a statistical mismatch analysis has been carried out to determine the deviation of resonance with etching time and ascertain maximum device yield. With our in-house back-end of line metal-layer release, this sensor can be monolithically embedded in the same substrate as standard CMOS integrated circuits, resulting in a significant cost and area reduction.

In this paper, we present a study of the quality factor (Q) behavior of a CMOS-MEMS resonator under different conditions of temperature and pressure. The device has been manufactured using standard 250 nm CMOS technology followed by an in-house BEOL metal-layer release wet etching. The manufactured sensor is used as a pressure estimator based on the variation of Q. Experiments have demonstrated an inverse relationship between the resonator Q and temperature in different pressure regimes. The initial Q has decreased to 0.80*Q at 100 Pa when the temperature changed from 300 K to 360 K, and to 0.65*Q at atmospheric pressure under the same temperature span. The static capacitance variations of the device with temperature have also been measured.

Micro machined resonant pressure sensors have rapidly grown into a major type of MEMS products over the past two decades. This paper presents the mathematical modelling of squeeze film damping in a MEMS resonant pressure sensor by MATLAB wherein structural and performance parameters of the device i.e. quality factor, capacitance and sensitivity are optimized relative to pressure. The change in quality factor is aimed to be optimized in order to enhance the modelling of the sensor and improve the overall sensitivity of the complete architecture. The sensor mass being 0.4 μg was designed with optimum structural parameters of 140 μm × 140 μm × 8 μm having 6 × 6 perforations along the row and column of the plate respectively to yield an enhanced quality factor of 62 and reduced damping coefficient of 4.2 μN-s/m at atmospheric pressure.

Wireless implantable devices have revolutionized the field of biomedical engineering for as long as adequate power supplies are conjured. This paper presents an ultrasonic power link front-end interfaced with a capacitive micromachined ultrasonic transducer (CMUT). The ultrasonic power link front-end consists of a rectifier, a charge pump, a clock extractor and a phase generator. The power link front-end designed in 0.18-μm CMOS process provides a 17 V DC supply for the implant microsystem, e.g. neural stimulator. It achieves an overall power efficiency of 0.3% in simulation.