High-sensitivity flexible PPG sensor based on non-destructive vertical stacking of multi-wavelength optical sensors and source-gated transistors

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"The advancement of science and technology has led to an increase in human life expectancy. Nevertheless, escalating costs of managing chronic diseases pose a significant societal burden. It becomes imperative to focus on increasing healthy life expectancy. In peripheral artery disease (PAD) early detection is essential, and the outcomes of surgical interventions may improve if carefully monitored.
This project will develop a proof of concept flexible and cost-effective multipoint photoplethysmogram (PPG) system for monitoring blood circulation, detection of PAD, localization of blockage and response during revascularization surgery at several sites on the legs or feet enabling treatment to-target. We will fuse sensor and signal conditioning expertise within the South Korean and UK groups to implement an array of flexible optical sensors capable of detecting PPG signals, vertically integrated with source-gated transistor-based amplification circuits for low-power and minimally invasive on-skin monitoring.
Conventional PPG sensors are sensitive to movement and ambient, resulting in significant noise and difficulties in achieving accurate measurements. To fabricate a photodetector, we will select and synthesize materials that respond to wavelengths suitable for reflection but not absorption by body tissues. The selected material will be used for producing the photodetector using the Gachon facilities. To address signal strength limitations, we will concurrently develop a novel low-voltage organic source-gated transistor-based amplifier (Surrey and Gachon cleanrooms). Once these electronic devices are fabricated, we will vertically stack devices using non-destructive methods to achieve downsizing and densification, followed by building sparse arrays with multiple sensing sites.
Through the flexible substrate-based, low-voltage operation, and high-gain PPG sensor, real-time monitoring of various cardiovascular health indicators becomes feasible, providing specialists a high-value, low-cost tool for monitoring healing for improved outcomes. Complementary competencies and facilities enable the realization of vertically stacked sensors and conditioning electronics, leading to downsizing and densification. This know-how translates to other applications of sensors in medicine, wellbeing, and ecology.
With technology exchange and knowledge sharing between two countries, new electronic components can be developed and applied, fostering effective innovation and competitiveness. Utilizing advanced technologies nurtures the next generation of expert researchers. The Korea-UK collaborative initiative enhances research leadership and impactful scientific development, fostering mutual growth of research capabilities and promoting efficiency through shared facilities and resources. All these directions have in common the need for low-power, low-cost, and imperceptible high-quality sensors. We envisage the current project as an essential steppingstone toward building effective international consortia ideally equipped for tackling major societal challenges. "