Differential Tissue-Coupled Powering for Battery-Free Injectable Electroceuticals

Electroceutical implants that deliver targeted neural stimulation have shown therapeutic potential for a wide range of neurological and peripheral disorders, yet wirelessly powering ultra-miniaturized, fully injectable systems remains a critical challenge. Here, we report a Thread-like Injectable Neural TechnologY (TINY) based on differential tissue-coupled powering (DTCP), which transmits energy through tissue using MHz-range differential fields generated by a compact, wearable transmitter. DTCP allows power harvesting to scale with implant length rather than cross-section, enabling a flexible, thread-like implant that integrates a custom ASIC with PEDOT-coated receiver and stimulation electrodes. Benchtop experiments in tissue-mimicking agar phantoms characterize power-transfer efficiency (PTE) and reveal that PTE increases with implant length while remaining highly tolerant to angular misalignment. In vivo tests in rat hindlimbs further demonstrate wireless sciatic nerve activation through tissue at centimeter-scale depths, confirming effective transcutaneous energy delivery for neurostimulation. A 20-day implantation study provides a short-term/subacute assessment of device positioning and local tissue response. Together, these findings address long-standing challenges in wirelessly powering injectable electroceuticals and establish DTCP as a scalable and alignment-robust powering strategy for future minimally invasive neuromodulation therapies.