Designing low-cost, wearable triboelectric energy harvesters (TEHs) from e-textile and foam, and developing high-efficiency SSHI power management circuits to convert human motion into usable electrical energy for wearable electronics.
Triboelectric energy harvesters generate electricity through contact-and-separation of dissimilar materials, converting ambient mechanical energy directly to charge. This research explored how everyday, low-cost materials — foam and e-textile — could serve as effective triboelectric pairs for flexible, scalable wearable harvesters, manufacturable without nanoscale processes.
A central challenge was bridging the gap between raw AC triboelectric output and usable DC power. Standard full-wave bridge rectifiers waste significant energy due to source-capacitance charging losses at the low frequencies (1–10 Hz) of human motion. This project adapted the SSHI (synchronized switching harvesting on inductor) rectifier strategy — previously applied only to piezoelectric harvesters — to the unique constraints of TEH devices, whose source capacitance varies dramatically with plate gap distance.
Key insight: By co-designing the TEH with a stabilizing multilayer pairing capacitor, the source capacitance variation is bounded to ≤ 30%, enabling the LC resonance loop to reliably flip the harvester voltage at each zero-crossing of source current. This eliminates the dominant energy-loss mechanism of bridge rectifiers and recovers the negative half-cycle that bridge rectifiers often miss entirely in contact-separation mode TEHs.
1 · Low-cost wearable TEH design. Foam and e-textile as the active triboelectric pair — flexible, wearable, off-the-shelf. A multilayer sandwich pairing capacitor (copper / PE / copper, ~12.5 µm dielectric) is integrated into the harvester structure, stabilizing total source capacitance across the full contact–separation range (100 µm–10 mm gap). A shoe-sole variant (TriboWalk) incorporates four removable tribo-elements per sole to capture gait timing and ground contact force.
2 · New dynamic impact-force model. Existing V–Q–x models for TENGs assumed static contact forces. In practice, the fast contact-and-separation cycle creates a dynamic impact force that dominates charge generation and causes frequency shifts in the voltage waveform. A new theoretical model incorporating Fe = F(1 + √(1 + ẋ²/gδₛₜ)) was developed and validated at 6 Hz input frequency.
3 · Parallel SSHI interface (p-SSHI). A symmetric n-MOSFET switching pair in parallel with the TEH, timed to τ = π√(LC_T) ≈ 222 µs, flips the harvester voltage at each current zero-crossing via LC resonance. Validated across 60 experimental trials; consistently outperforms bridge rectifier by up to 3.43×.