In Vivo Wireless Powering of a Long-Acting Nanofluidic Drug Delivery Implant

Wireless power transfer (WPT) is a key enabler for long-term operation of implantable medical devices, eliminating the need for percutaneous drivelines and frequent surgical device replacements. This paper presents the design and validation of a fully wireless, rechargeable implantable drug delivery system (nDS) with an integrated power management and control system, specifically developed for use in freely moving animal models. The proposed system consists of a subcutaneous implant with an inductive power receiver and an external, backpack-mounted power transmitter that dynamically adjusts energy delivery in response to real-time implant feedback. A closed-loop power control strategy, implemented via Bluetooth Low Energy (BLE) communication, ensures adaptive power transfer to maintain system efficiency despite coil misalignment and animal movement. Building on a previously characterized inductive link, the present work extends the validation from benchtop characterization to in vivo operation in freely moving rats, demonstrating safe and repeatable wireless battery recharging of an implantable nanofluidic drug delivery system. Across four in vivo recharging sessions, the median average power transfer efficiency during constantcurrent phase was 22.9% with a median average power delivered to the load of 104.7 mW. The charging sessions lasted from 90 (first) to 30 (last) minutes, performed once per week over 4 weeks. The proposed closed-loop WPT implementation enabled reliable battery recharging within clinically relevant time scales while maintaining operation in compliance with thermal safety constraints, thereby supporting chronic, fully untethered drug delivery studies in small animals.