Wireless Power Delivery Techniques for Miniature Implantable Bioelectronics

Abstract

Progress in implanted bioelectronic technology offers the opportunity to develop more effective tools for personalized electronic medicine. While there are numerous clinical and pre‐clinical applications for these devices, power delivery to these systems can be challenging. Wireless battery‐free devices offer advantages such as a smaller and lighter device footprint and reduced failures and infections by eliminating lead wires. However, with the development of wireless technologies, there are fundamental tradeoffs between five essential factors: power, miniaturization, depth, alignment tolerance, and transmitter distance, while still allowing devices to work within safety limits. These tradeoffs mean that multiple forms of wireless power transfer are necessary for different devices to best meet the needs for a given biological target. Here six different types of wireless power transfer technologies used in bioelectronic implants—inductive coupling, radio frequency, mid‐field, ultrasound, magnetoelectrics, and light—are reviewed in context of the five tradeoffs listed above. This core group of wireless power modalities is then used to suggest possible future bioelectronic technologies and their biological applications.

Injectable wireless microdevices: challenges and opportunities

“…Nonetheless, the unit cost of ASICs will drop precipitously once the production volume increases. Table 1 also indicates that, although multiple wireless powering modalities exist in the sub-mm scale, near/mid-field RF, ultrasonic, and optical are the most promising (Khalif et al 2021 ; Singer and Robinson 2021 ; Cai and Gutruf 2021 ; Won et al 2021 ). Each method offers trade-offs, and thus the best powering mechanism will depend on the application.…”

Flexible and Stretchable Bioelectronics

“…This delamination due to disruption in insulation barriers or due to repetitive stretching of the skin or tissue may cause a lack of conformability, which increases the impedances and decreases the signal-to-noise ratio (SNR). Miniaturized ultra-small implantable technology, such as “neural dust” [ 29 ] and “Stim dust” [ 30 ], enables access to small target areas and can be implanted anywhere in the body, and interfaces directly with the tissue or organ. Miniaturized biosensors also require small volumes for biological assays.…”

Ferroelectrically augmented contact electrification enables efficient acoustic energy transfer through liquid and solid media

“…However, it is difficult to utilize electromagnetic-based (EM-based) WET, which is a generally used method, in those areas such as water and the body where wireless charging is most needed. 2,12–15 For example, induction coupling methods have limitations in miniaturization, because the size of the coil greatly depends on the strength and efficiency of the transmission, and cannot be used in body-inserted sensors, because tissue burn due to generated heat during induction is inevitable. 16,17 Microwaves, another form of EM-based WET, which can transmit energy relatively far away, are quickly attenuated in condensed matter ( e.g.…”