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1. High surface area reverse electrowetting energy harvesting with power conditioning circuitry for self-powered motion sensors

   https://doi.org/10.1117/12.2587541  

   Adhikari, Pashupati R. ; Biswas, Dipon K. ; Tasneem, Nishat T. ; Reid, Russell C. ; Mahbub, Ifana ( April 2021 , SPIE Defense + Commercial Sensing)

   Dutta, Achyut K. ; Balaya, Palani ; Xu, Sheng (Ed.)

   Monitoring human health in real-time using wearable and implantable electronics (WIE) has become one of the most promising and rapidly growing technologies in the healthcare industry. In general, these electronics are powered by batteries that require periodic replacement and maintenance over their lifetime. To prolong the operation of these electronics, they should have zero post-installation maintenance. On this front, various energy harvesting technologies to generate electrical energy from ambient energy sources have been researched. Many energy harvesters currently available are limited by their power output and energy densities. With the miniaturization of wearable and implantable electronics, the size of the harvesters must be miniaturized accordingly in order to increase the energy density of the harvesters. Additionally, many of the energy harvesters also suffer from limited operational parameters such as resonance frequency and variable input signals. In this work, low frequency motion energy harvesting based on reverse electrowetting-ondielectric (REWOD) is examined using perforated high surface area electrodes with 38 µm pore diameters. Total available surface area per planar area was 8.36 cm2 showing a significant surface area enhancement from planar to porous electrodes and proportional increase in AC voltage density from our previous work. In REWOD energy harvesting, high surface area electrodes significantly increase the capacitance and hence the power density. An AC peak-to-peak voltage generation from the electrode in the range from 1.57-3.32 V for the given frequency range of 1-5 Hz with 0.5 Hz step is demonstrated. In addition, the unconditioned power generated from the harvester is converted to a DC power using a commercial off-theshelf Schottky diode-based voltage multiplier and low dropout regulator (LDO) such that the sensors that use this technology could be fully self-powered. The produced charge is then converted to a proportional voltage by using a commercial charge amplifier to record the features of the motion activities. A transceiver radio is also used to transmit the digitized data from the amplifier and the built-in analog-to-digital converter (ADC) in the micro-controller. This paper proposes the energy harvester acting as a self-powered motion sensor for different physical activities for wearable and wireless healthcare devices. 

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2. Cyber Physical Implementation of Improved Distributed Secondary Control of DC Microgrid

   https://doi.org/10.1109/icpee50452.2021.9358705  

   Pragallapati, Nataraj ; Ranade, Satish J ; Lavrova, Olga ( January 2021 , 2021 1st International Conference on Power Electronics and Energy (ICPEE))

   null (Ed.)

   This paper presents a cyber physical system implementation of an improved distributed secondary control (IDSC) scheme of islanded dc microgrid (DCMG). The IDSC scheme mitigates the hidden issues of primary control with included droop technique for the distributed generation unit (DGU) in a DCMG by providing the adjustable voltage compensation, improves voltage regulation and enhances the current sharing of all DGUs. The voltage compensation of IDSC is the resultant of two voltage components, i.e., average distributed integral voltage controller and average current controller. The dynamic consensus algorithm is used to obtain the global average values in the for distributed secondary controlusing relatively low bandwidth communication. The impact of communication time delay on the stability in IDSC based DCMG with two DGUs is presented. The performance of IDSC scheme is validated on a microgrid scenario, which includes parallel connection of four DGUs and common load. The real-time cyber physical system of DCMG is implemented on OP AL-RT test platform that combines the device layer on FPGA, control and cyber layers on CPU of OP5700 by using eFPGASim and RT-LAB. 

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3. Fast and Secure Operation of Voltage Source Inverter based DERs using Model Predictive Droop Control

   https://doi.org/10.1109/ECCE.2018.8558323  

   Alhosaini, Waleed ; Mahmud, Mohammad Hazzaz ; Zhao, Yue ( September 2018 , Fast and Secure Operation of VSI based DERs using Model Predictive Droop Control)

   Reliability of the power grid can be improved by the use of microgrids (MGs) concept, which regulates the voltage and frequency at the point of common coupling (PCC) during normal and/or faulty conditions. Droop characteristics based hierarchical control strategies are commonly used in MGs, where power converters can operate in parallel. However, the need of multiple control loops not only adds complexity to the controller design, but also reduces the dynamic response of the system. In the future power system, grid-tied converters with fast dynamic response are desired to handle the uncertainties induced by high penetration of distributed energy resources. Therefore, this paper presents a novel model predictive control to ensure fast dynamic response of high power three-level converters in stand-alone operating mode as well as grid-tied operating mode. The proposed controller is applied to a MG which consists of a solar inverter connected in parallel with an energy storage system to the PCC, where a local load is tied. Both simulation and experimental results are presented to demonstrate robustness and the high dynamic performance of the proposed controller under rapidly changing atmospheric conditions and different grid operating modes. 

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4. Self-Powered Motion Tracking Sensor Integrated with Low-Power CMOS Circuitry

   https://doi.org/10.1109/ISCAS51556.2021.9401440  

   Tasneem, Nishat T. ; Biswas, Dipon K. ; Mahbub, Ifana ; Adhikari, Pashupati R. ; Reid, Russell ( May 2021 , 2021 IEEE International Symposium on Circuits and Systems (ISCAS))

   null (Ed.)

   This paper presents a motion-sensing device with the capability of harvesting energy from low-frequency motion activities that can be utilized for long-term human health monitoring. The energy harvester used in the proposed motion sensor is based on the mechanical modulation of liquid on an insulated electrode, which utilizes a technique referred to as reverse electrowetting-on-dielectric (REWOD). The generated AC signal from the REWOD is rectified to a DC voltage using a Schottky diode-based rectifier and boosted subsequently with the help of a linear charge-pump circuit and a low-dropout regulator (LDO). The constant DC voltage from the LDO (1.8 V) powers the motion-sensing read-out circuitry, which converts the generated charge into a proportional output voltage using a charge amplifier. After amplification of the motion data, a 5-bit SAR-ADC (successive-approximation register ADC) digitizes the signal to be transmitted to a remote receiver. Both the CMOS energy harvester circuit including the rectifier, the charge-pump circuit, the LDO, and the read-out circuit including the charge amplifier, and the ADC is designed in the standard 180 nm CMOS technology. The amplified amplitude goes up to 1.76 V at 10 Hz motion frequency, following linearity with respect to the frequency. The generated DC voltage from the REWOD after the rectifier and the charge-pump is found to be 2.4 V, having the voltage conversion ratio (VCR) as 32.65% at 10 Hz of motion frequency. The power conversion efficiency (PCE) of the rectifier is simulated as high as 68.57% at 10 Hz. The LDO provides the power supply voltage of 1.8 V to the read-out circuit. The energy harvester demonstrates a linear relationship between the frequency of motion and the generated output power, making it suitable as a self-powered wearable motion sensor. 

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5. Multichannel Electrophysiological Recording With Spike Detection and Sorting in a Duty-Cycled Wireless Optogenetic Headstage

   https://doi.org/10.1109/JSEN.2023.3313520  

   Tasneem, Nishat T. ; Biswas, Dipon K. ; Reza, Sakib ; Becker, April ; Mahbub, Ifana ( November 2023 , IEEE Sensors Journal)

   Neural signal recording and optical stimulation using implantable devices have become a ubiquitous method to treat brain disorders, yet there lie some shortcomings, such as size, weight, and functionalities of the implants. This work presents a commercial off-the-shelf (COTS) component-based miniaturized wireless optogenetic headstage with simultaneous optical stimulation and electrophysiological recording for freely moving rats. The system includes a battery-based neural stimulator consisting of a low-dropout (LDO) regulator, an oscillator, and a μ LED. The electrophysiological signal recording system includes an intracortical neural probe implemented on a shape memory polymer (SMP) substrate, an array of neural amplifiers with an integrated analog-to-digital converter (ADC), a transceiver IC, and a ceramic antenna. A digital sub-1-GHz transceiver integrated with a low-power microcontroller (MCU) is used to transmit the acquired neural data to a remote receiver unit, followed by offline spike detection and sorting in LabVIEW. The front-end recording amplifiers provide a gain of 45.7 dB with the input-referred noise of 2.4μVrms . The integrated multiplexer (MUX) with the ADC allows sampling of the amplified voltage at a configurable sampling rate of 160–480 kSamples/s. The total power consumption of the stimulation and the recording system is 23 mW. The dimension of the headstage device is 13.5×21.3 mm, weighing 4 g without the battery. The system is experimentally validated in an in vivo setting by placing the headstage on the head of a male rat and recording the neural signals from the ventral tegmental area (VTA) of the brain. This integrative neural signal recording and spike sorting approach would be useful for the development of a closed-loop neuromodulation system. 

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