Article Highlight | 29-Dec-2025

An ultra‑thin wearable thermoelectric paster based on structured organic ion gel electrolyte

Shanghai Jiao Tong University Journal Center

An Ultra‑Thin Wearable Thermoelectric Paster Based on Structured Organic Ion Gel Electrolyte

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  • All-solid-state organic ion gel electrolyte with superior thermal tolerance capability and environmental stability can well penetrate into the electrodes of thermoelectric paster to ensure an excellent interfacial contact.
  • Inspired by the “onion epidermal cells” structure, the organic ion gel electrolyte supported by a porous polymer skeleton offers a considerable ZT figure according to the thermal expansion effect.
  • Considering the compatibility between electrode and electrolyte, an ultrathin and skin-attachable i-TE paster was assembled to acquire a satisfactory Seebeck coefficient and used in various applications.
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Credit: Zhijian Du, La Li*, Guozhen Shen*.

Wearable electronics still hunt for a thin, skin-safe energy source that harvests low-grade body heat without bulky heat-sinks or toxic tellurides. Now Prof. La Li and Prof. Guozhen Shen at Beijing Institute of Technology unveil an “ionic-skin” paster—only 0.2 mm thick—that converts a 1 °C temperature difference into 28 mV, stores the energy as a thermally rechargeable supercapacitor, and even recognizes materials by touch temperature.

Why the i-TE Paster Matters
• Record Seebeck: 28 mV K-1 for ionic thermoelectrics—three-fold higher than best-in-class hydrogels—thanks to Soret-driven Li⁺ diffusion inside an “onion-epidermal-cell” PVDF-HFP/PEO nano-porous scaffold.
• All-solid & Safe: Organic carbonate gel (EC/DMC/LiTf) immobilized in a polymer network shows zero leakage at 50 °C for >500 h; passes ISO 10993 skin-irritation test on mice.
• Multi-functional: Same patch acts as TCSC (1.3 % energy-conversion efficiency), contact/non-contact thermometer (0.8 cm air-gap warning), AI-ready material identifier, and 925 nm light-driven synapse emulator.

Innovative Design & Features
• Electrolyte Engineering: 1 M LiTf in EC-rich solvent (1:2 DMC:EC) maximizes ionic solvation yet keeps viscosity low; ZT reaches 0.35—matching commercial Bi2Te3 films.
• Laser-sculpted Electrode: CO2-laser converts 100 µm PI into 3-D graphene foam, spray-coated with PANI to create 1.9 kΩ sq-1 compliant film that survives 40° bending >3 000×.
• Device Architecture: Symmetric “sandwich” (PANI-C@PI // gel // PANI-C@PI) packaged in breathable PI/PU laminate; total mass <40 mg cm-2, water-vapor transmission 18 g m-2 day-1.

Applications & Outlook
• Self-powered Health Patch: 6-cell array worn on forearm charges 1 mF supercapacitor to 0.35 V in 10 min using 3 K skin-to-ambient ΔT; powers BLE temperature beacon for 30 min after 1 h wear.
• Material-ID Glove: Fingertip patch discriminates Al, Cu, wood, rubber within 2 s via transient thermal voltage; 96 % accuracy when coupled to on-board TinyML classifier.
• Non-contact Safety Alert: Detects 80 °C coffee cup at 8 mm distance and triggers vibration motor before skin contact, mimicking TRP-ion-channel warning biology.
• Photothermal Synapse: Under 925 nm IR light the patch exhibits learning-forgetting weight updates, offering a self-powered receptor for soft robotics and VR haptics.

The team is now scaling the paster to 10 × 10 cm2 modules using roll-to-roll slot-die coating, and exploring sodium-ion gel chemistries for fully biocompatible implants. Expect the first medical-grade i-TE patches in pilot trials later this year.

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