Dynamic network‑ and microcellular architecture‑driven biomass elastomer toward sustainable and versatile soft electronics

Soft sensors that feel gentle taps yet survive 500 % stretch still rely on petro-based rubbers and energy-intense foaming. A ZJUT–USTC–Xi’an Jiaotong team led by Prof. Shanqiu Liu and Prof. Jingguo Li now twists lipoic-acid chemistry into an ultralight (~0.25 g cm^-3) biomass conductive elastomer that self-foams at room temperature under 2 MPa CO₂, heals in 5 h and recycles five times without property loss. The resulting “micro-spring” lattice delivers a gauge factor of 4.8 under 1 % strain, rebounds 93 % after 200 % pull and tracks handwriting, heartbeat and ball drops in real time.

Why This Matters

• Mild, Scalable Foaming: CO₂ plasticises dynamic disulfide/H-bond networks at 25 °C—80 % less energy and pressure than super-critical routes—yet yields 70 % porosity and 5× volume expansion.
• Micro-Spring Sensitivity: Closed cells act as strain amplifiers; GF jumps 3× in tension and 2.75× in compression versus the dense film, while cyclic drift stays <1 % over 100 cycles.
• Self-Healing & Closed-Loop Recycling: Cut samples rejoin at room temp, restoring 90 % mechanical and 98 % electrical performance; ethanol depolymerisation separates nano-fillers, ionic liquid and polymer for direct reuse.
• Green Feedstock: All building blocks (lipoic acid, SiO₂, imidazolium sulfate) are bio-sourced or recyclable, cutting cradle-to-gate CO₂ footprint by 45 %.

Innovative Design & Features

• Dynamic Crosslink Toolbox: Disulfide metathesis provides covalent reversibility; ionic liquid forms CO₂-affinity sites that lower nucleation energy and furnish long-range ionic pathways (~0.65× dense-state conductivity).
• Tunable Architecture: Pore size (20–200 µm) and density are dialled by CO₂ pressure (1–5 MPa) and nano-filler loading, giving density as low as 0.18 g cm^-3—light enough to rest on a dandelion.
• Multi-Modal Sensing: Detects <1 % micro-strain, 50 µN contact force, 0.3 s rapid deformation and 5 °C temperature steps; handwriting and droplet impacts generate distinct, reproducible resistance patterns.

Applications & Future Outlook

• Wearable Health Patches: 300-µm film laminated on fabric monitors pulse, respiration and joint flexion with <0.05 s lag, surviving 10 000 bend cycles.
• Soft-Robot Skin: Foam strips wrapped around grippers provide tactile feedback for delicate fruit handling, maintaining sensitivity after 500 % inflation.
• Circular Manufacturing: Team is scaling a roll-to-roll CO₂ chamber (1 m min^-1) and exploring wireless BLE modules that dissolve in ethanol for tech-metal recovery.

By marrying a biomass backbone with CO₂-blown micro-springs, the work offers a production-ready route to sensing foams that are light, tough, healable and endlessly reusable—pointing toward truly sustainable soft electronics that can be worn, folded, recycled and reborn.