(A) study on realization of ultralow-power organic/inorganic pulse oximetry sensors with high reliability.

Abstract

As the number of consumers with purchasing power increases due to the aging of the world and the increase of the middle class, the pursuit of high quality life leads to interest in healthcare is expanding according to the demand of consumers. While existing medical devices are a form of passive health screening, new healthcare devices that are fused with IT are changing their paradigm to devices that are active to the user. Among them, the heartrate and oxygen saturation sensor, which detects the information inside the blood vessel using light in a non-invasive manner, has been variously applied to the wearable healthcare industry due to its easiness of real-life utilization. In this study, we implemented heartrate and oxygen saturation sensor with novel form-factor by replacing light emitting diodes (light emitting units) and photodiodes (light receiving units) used in existing pulse oximetry with organic light emitting diodes and organic photodiodes. In the present study, the optical power distribution on the skin surface of the green and red wavelengths used for oxygen saturation was confirmed through skin optics modeling. In this study, the optical power distribution on the skin surface of the wavelengths used in the sensor was confirmed using optical modeling simulation, based on such results, the organic photodiode wraps around the organic light emitting diode using the pattern freedom characteristic of the organic semiconductor device. Also, the heart rate and oxygen saturation sensor with optimal light - receiving efficiency were fabricated by calculating the SNR according to the size of the organic photodiode. The implemented patch-type reflective oxygen saturation sensor was able to extract heart rate and oxygen saturation signals from each body part with about 10 to 20 times less power consumption than commercial sensors through the efficient light receiving structure. In addition, through combining organic and inorganic devices, we have proposed ultra-low-power hybrid PO sensors that are practical, durable, and accurate. Contrary to common belief, we could still collect sufficient photons even with an reflective type sensor using light with long wavelengths with deep skin penetration depth. Furthermore, we have also confirmed through experiment and simulation, that we could achieve a PO sensor with ultra-low power consumption by designing an efficient photodetector structure. We have successfully extracted PPG signals and oxygen saturation levels with a low power consumption below 40 μW using the hybrid POs, which could maintain sensor performance over 90% even after 40 days of continuous operation. Also, by verifying the photon movement in biomedium layers, we have proved that hybrid POs with reflective type configuration could efficiently detect information from the pulsation part of the body.We proposed an ultra-low-power sensor structure through efficient light collection through organic pulse oximeters and hybrid pulse oximeters, and we expect that the wearable healthcare monitoring system will contribute to all-day monitoring.