Wide dipole antennas for wireless powering of miniaturised bioelectronic devices

Biomedical electronic implants require a power source to operate. Miniaturised implants can preclude batteries and as implant dimensions reduce further, inductive power transfer no longer becomes the optimum strategy for wireless power delivery. Wide dipole antennas are proposed as an alternative power transmitter for long and thin implants. A miniaturised bioelectronic device measuring 1 mm by 1 mm by 20 mm was fabricated, wirelessly powered and used to stimulate retinal ganglion cells to provide biological validation of its functionality. Optimised wide dipole antennas operating in the GHz range for implant depths of 5 mm to 35 mm in 5 mm steps were simulated, fabricated and measured. Saline solution was used as a biological tissue phantom for power transfer efficiency measurements. The maximum safe deliverable power to the device was 1.7 mW in simulation and 1.3 mW in measurement at power transfer efficiencies of 15% and 11% respectively. The work herein confirms that wide dipole transmitting antennas are suitable for radiative near field power transfer to long and thin implants. This power transfer technique could be used for implants that are injectable, deliverable via catheter and minimally invasive, advancing the aim to create smaller more innovative electronic implantable devices.