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Abstract Developing nerve grafts with intact mesostructures, superior conductivity, minimal immunogenicity, and improved tissue integration is essential for the treatment and restoration of neurological dysfunctions. A key factor is promoting directed axon growth into the grafts. To achieve this, biohybrid nerves are developed using decellularized rat sciatic nerve modified by in situ polymerization of poly(3,4‐ethylenedioxythiophene) (PEDOT). Nine biohybrid nerves are compared with varying polymerization conditions and cycles, selecting the best candidate through material characterization. These results show that a 1:1 ratio of FeCl₃oxidant to ethylenedioxythiophene (EDOT) monomer, cycled twice, provides superior conductivity (>0.2 mS cm⁻¹), mechanical alignment, intact mesostructures, and high compatibility with cells and blood. To test the biohybrid nerve's effectiveness in promoting motor axon growth, human Spinal Cord Spheroids (hSCSs) derived from HUES 3 Hb9:GFP cells are used, with motor axons labeled with green fluorescent protein (GFP). Seeding hSCS onto one end of the conduit allows motor axon outgrowth into the biohybrid nerve. The construct effectively promotes directed motor axon growth, which improves significantly after seeding the grafts with Schwann cells. This study presents a promising approach for reconstructing axonal tracts in humans. 

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. 

To maximize the capabilities of minimally invasive implantable bioelectronic devices, we must deliver large amounts of power to small implants; however, as devices are made smaller, it becomes more difficult to transfer large amounts of power without a wired connection. Indeed, recent work has explored creative wireless power transfer (WPT) approaches to maximize power density [the amount of power transferred divided by receiver footprint area (length × width)]. Here, we analyzed a model for WPT using magnetoelectric (ME) materials that convert an alternating magnetic field into an alternating voltage. With this model, we identify the parameters that impact WPT efficiency and optimize the power density. We find that improvements in adhesion between the laminated ME layers, clamping, and selection of material thicknesses lead to a power density of 3.1 mW/mm2, which is over four times larger than previously reported for mm-sized wireless bioelectronic implants at a depth of 1 cm or more in tissue. This improved power density allows us to deliver 31 and 56 mW to 10 and 27-mm2 ME receivers, respectively. This total power delivery is over five times larger than similarly sized bioelectronic devices powered by radiofrequency electromagnetic waves, inductive coupling, ultrasound, light, capacitive coupling, or previously reported magnetoelectrics. This increased power density opens the door to more power-intensive bioelectronic applications that have previously been inaccessible using mm-sized battery-free devices. 

This paper presents the design, implementation, and experimental evaluation of a wireless biomedical implant platform exploiting the magnetoelectric effect for wireless power and bi-directional communication. As an emerging wireless power transfer method, magnetoelectric is promising for mm-scaled bio-implants because of its superior misalignment sensitivity, high efficiency, and low tissue absorption compared to other modalities [46, 59, 60]. Utilizing the same physical mechanism for power and communication is critical for implant miniaturization, but low-power magnetoelectric uplink communication has not been achieved yet. For the first time, we design and demonstrate near-zero power magnetoelectric backscatter from the mm-sized implants by exploiting the converse magnetostriction effects. The system for demonstration consists of an 8.2-mm3 wireless implantable device and a custom portable transceiver. The implant's ASIC interfacing with the magnetoelectric transducer encodes uplink data by changing the transducer's load, resulting in resonance frequency changes for frequency-shift-keying modulation. The magnetoelectrically backscattered signal is sensed and demodulated through frequency-to-digital conversion by the external transceiver. With design optimizations in data modulation and recovery, the proposed system archives > 1-kbps data rate at the 335-kHz carrier frequency, with a communication distance greater than 2 cm and a bit error rate less than 1E-3. Further, we validate the proposed system for wireless stimulation and sensing, and conducted ex-vivo tests through a 1.5-cm porcine tissue. The proposed magnetoelectric backscatter approach provides a path towards miniaturized wireless bio-implants for advanced biomedical applications like closed-loop neuromodulation.