Shibam Debbarma

The Mitacs Accelerate Internship Program, in partnership with McGill University, the University of Alberta, and iMD Research, a Montreal-based company for biomedical devices, that I participated in.

A smart, sensor-based wristwatch was intended to be developed during the 1st lockdown of COVID-19 to monitor patients who tested positive and patients at risk, like senior citizens. The device is designed to monitor if the person has a sudden rise in temperature or indicators of respiratory distress.

The wristwatch can monitor vitals like heart rate, blood oxygen saturation, breathing patterns, body temperature, and body posture. I worked closely with the smart sensors for photoplethysmography (PPG), temperature, and accelerometers to collect data from healthy participants and analyze them in MATLAB to extract the vitals.

I participated in the Mitacs Accelerate Internship Program in partnership with McGill University and AntiSense, a Montreal-based program that aims to develop intelligent sensing devices.

This project aims to develop a gas sensor array-based printed circuit board (PCB) for sensing carbon dioxide (CO2), alcohol, and other gases from the environment.

MY ROLE
I selected and procured the necessary gas sensors, including CO2, alcohol, ammonia, and acetone, from different distributors. I prototyped, soldered, and tested the PCB hardware, developed firmware for digitally controlling gas pumps and valves, and tested the gas sensor array in controlled gas chambers and open-air environments. I was fully liable for designing the hardware prototype in this project.

A sensor-array-based smart wireless flexible device interfaced with wearables like headbands or mouthguards to monitor vital signs like heart rate, blood oxygen saturation, temperature, body posture, and sleep assessments.

MY ROLE
I conducted the initial research using several sensors like the photoplethysmography (PPG) sensor, temperature sensor, accelerometers, and EEG/EOG electrodes to acquire biosignals for assessing the vitals.

I conducted circuit simulations, designed multilayer flexible printed circuit boards (PCBs), assembled and tested hardware, developed firmware, and prototyped flexible wireless systems for biopotential measurements.

I extensively researched signal processing and sensor-fusion techniques to remove artifacts from the measured biosignals.

POTENTIAL APPLICATIONS
The prototypes are integrated with headbands for remote electrooculogram (EOG) measurements and mouthguards for intra-oral electroencephalogram (EEG) measurements.

A microcontroller-based, battery-operated simulator circuit designed in PCB capable of generating signals equivalent to human body impedance (especially thoracic region).

I designed a printed circuit board (PCB) with analog and digital circuit blocks to generate a novel continuously variable voltage-controlled resistor (VCR) that acts as the human body impedance. I did a detailed study on the development of the novel voltage-controlled resistor (VCR) circuit using junction field-effect transistors (JFETs), MOSFETs, and operational amplifiers (OpAmps), which helped us get a US patent.

To control the parameters of the bioimpedance simulator board, I developed a GUI and a simple firmware (using C++) for the microcontroller-Bluetooth unit present on the board.

Potential applications of this bioimpedance simulator include testing and calibrating medical instruments such as the impedance cardiograph.

A circuit for realizing a precise and linear floating resistor using metal-oxide-semiconductor field-effect transistor (MOSFET) devices is disclosed. A linear floating voltage-controlled resistor (LFVCR) is achieved using a MOSFET with a gate drive and substrate drive to provide feedback of the common-mode voltage across the source-drain terminals to the gate and substrate terminals. Two LFVCR circuits using matched MOSFET devices have independent substrates with an op amp-based negative feedback loop. They make a continuously variable precision and linear floating resistor, whose value can be controlled by varying voltage, current, and resistor. Further embodiments are disclosed for obtaining a resistor mirror circuit with multiple floating resistors, improving the linearity by using LFVCR circuits with complementary MOSFET devices, acknowledging a resistor with scaled-up resistance and an extended voltage range, achieving a resistor with scaled-down resistance and extended current range.

I implemented the entire circuit on the breadboard with MOSFET ICs and op amps and validated the proof of concept of this idea. The experimental results are in close agreement with the theoretical analysis.