Dynamic Foot Pump Assessment System (DFPAS) for Astronaut Circulatory Health in Microgravity

The Dynamic Foot Pump Assessment System (DFPAS) is a low-profile wearable insole designed to detect lower-limb venous pooling under simulated microgravity and deliver autonomous haptic feedback to re-engage the foot pump, thereby preserving circulatory health for astronauts and pilots during prolonged inactivity. DFPAS computes the perfusion index (PI) from multi-wavelength photoplethysmography (PPG), uses force-sensitive resistors (FSRs) for contact verification and qualitative activation monitoring, and incorporates an inertial measurement unit (IMU) to mitigate motion artifacts; all signals are processed via an on-device TinyML classifier on an ESP32 microcontroller. In preliminary head-down tilt tests (n=3) simulating microgravity, individualized PI deviations triggered a 10 Hz vibration motor for 2–3 seconds, yielding a mean 27% relative PI increase (paired t-test, p<0.05) and more frequent dorsiflexion events (2.4 ± 0.5 events/trial) compared to control sessions, with subjective reductions in foot swelling. Concurrent SpO2 remained stable (95.5% ± 1.2%), justifying PI’s superiority for local perfusion detection. The insole maintains <6 mm thickness and <150 g weight, operates 12–18 hours on a 1000 mAh Li-Po battery, and streams data via Bluetooth Low Energy (BLE) for adaptive thresholding. Ongoing validation includes expanded cohorts (n=5 planned by November 2025), parabolic flight testing, and integration of Red+Green+IR PPG and bioimpedance to enhance accuracy. Terrestrial applications for deep vein thrombosis (DVT) prevention in sedentary populations are under consideration. All symbols in this abstract are defined in the Nomenclature