Dynamic behaviors of ink-based flexible thin-film thermoelectric generator applied for harvesting human body waste heat

Highly flexible, low-cost wearable ink-based thin-film thermoelectric generator (TEG) is a promising technology for biological heat recovery and self-powered wearable sensors. Dynamic response characterization and performance prediction considering real-world application conditions are essential for improving the device usage in terms of operation; however, there is a lack of comprehensive dynamic behaviors analysis of typical thin-film TEG. In this study, a well-validated three-dimensional Multiphysics field coupled model is established to reveal basic dynamic behaviors of the TEG-skin system during start-up processes. Results show that: (1) the start-up processes approximately belong to a time-invariant second-order linear system; (2) higher skin-tissue initial temperature distribution causes remarkably larger output power, but shows negligible influence on variation mode; (3) different TEG initial temperatures have no influence on preliminary balance time, but cause different variation modes, i.e., overshooting and monotonic increasing; (4) blood perfusion can increase output power significantly by 16.33 %–23.3 %; (5) compared with PDMS and Kapton, the organic aerogel substrate with much lower thermal conductivity causes a tenfold increase in output power approximately but much longer preliminary balance time; (6) using temperature-dependent or constant thermoelectric properties causes 15 % difference in output power approximately; (7) different fluctuation forms and amplitudes of cold-side heat transfer coefficient have negligible influence on output power within the beginning 0–4 s, but then show significant influence. In addition, sensitivity analysis (including some critical parameters) and contact thermal resistance effect are discussed and addressed. This paper provides comprehensive dynamic behaviors modelling and analysis for designing and operating thin-film TEGs.