Modulation of the peripheral nervous system (PNS) has a great potential for therapeutic intervention as well as restore bodily functions. Recent interest has focused on autonomic nerves, as they regulate extensive functions implicated in organ physiology, chronic disease state and appear tractable to targeted modulation of discrete nerve units. Therapeutic interventions based on specific bioelectronic neuromodulation depend on reliable neural interface to stimulate and record autonomic nerves. Furthermore, the function of stimulation and recording requires energy which should be delivered to the interface. Due to the physiological and anatomical challenges of autonomic nerves, various forms of this active neural interface need to be developed to achieve next generation of neural interface for bioelectronic medicine. In this article, we present an overview of the state-of-the-art for peripheral neural interface technology in relation to autonomic nerves. Also, we reveal the current status of wireless neural interface for peripheral nerve applications. Recent studies of a novel concept of self-sustainable neural interface without battery and electronic components are presented. Finally, the recent results of non-invasive stimulation such as ultrasound and magnetic stimulation are covered and the perspective of the future research direction is provided.

The adoption of chronic implantable peripheral nerve-based prosthetic devices is currently hampered by the lack of a highly integrated neural signal acquisition system-on-chip (SoC). We report a ten-channel peripheral nervous system (PNS) electroneurogram (ENG) signal acquisition SoC within an implantable package. Requiring only four off-chip capacitors, this SoC can be co-encapsulated with flexible nerve electrodes and a resonant coil antenna to form a 3.4 cm³ and 3.9 g implantable device for chronic ENG acquisition. This SoC is inductively powered and controlled through a resonant coil at 22 MHz and transmits the digitized neural signal through a near-infrared LED (NIR-LED). Fabricated in 0.18-μm CMOS, each amplifier channel exhibits an input referred noise of 1.9 μVrms and a noise efficiency factor (NEF) of 4.0 within the signal bandwidth of 5.5 kHz. Each amplifier channel within the SoC is digitized with 10-bit resolution at 17.5 ksps, and the total power consumption (SoC and NIR-LED) is 4.4 mW when the NIR-LED is driven at 3 Mb/s. An electrode impedance measurement circuit with <10% magnitude and <8° angle error for measuring impedances up to 1 MΩ is also incorporated in this SoC. This wireless, low noise ENG acquisition SoC package has been validated in vivo while implanted on a rodent to acquire ENG from its sciatic nerve.

By monitoring brain neural signals, neural recorders allow for the study of neurological mechanisms underlying specific behavioural and cognitive states. However, the large brain volumes of non-human primates and their extensive range of uncontrolled movements and inherent wildness make it difficult to carry out covert and long-term recording and analysis of deep-brain neural signals. Here we report the development and performance of a stealthy neural recorder for the study of naturalistic behaviours in non-human primates. The neural recorder includes a fully implantable wireless and battery-free module for the recording of local field potentials and accelerometry data in real time, a flexible 32-electrode neural probe with a resorbable insertion shuttle, and a repeater coil-based wireless-power-transfer system operating at the body scale. We used the device to record neurobehavioural data for over 1 month in a freely moving monkey and leveraged the recorded data to train an artificial intelligence model for the classification of the animals’ eating behaviours.

Microneedle electrode (ME) is used to monitor bioelectrical signals by penetrating via the skin, and it compensates for a limitation of surface electrodes. However, existing fabrication of ME have limited in controlling the shape of microneedles, which is directly relevant to the performance and durability of microneedles as an electrode. In this study, a novel method using 3D printing is developed to control needle bevel angles. By controlling the angle of printing direction, needle bevel angles are changed. Various angles of printing direction (0–90°) are investigated to fabricate moldings, and those moldings are used for microneedle fabrications using biocompatible polyimide (PI). The height implementation rate and aspect ratio are also investigated to optimize PI microneedles. The penetration test of the fabricated microneedles is conducted in porcine skin. The PI microneedle of 1000 μm fabricated by the printing angle of 40° showed the bevel angle of 54.5°, which can penetrate the porcine skin. The result demonstrates that this suggested fabrication can be applied using various polymeric materials to optimize microneedle shape.

Surface electromyography (sEMG) sensors play a critical role in diagnosing muscle conditions and enabling prosthetic device control, especially for lower extremity robotic legs. However, challenges arise when utilizing such sensors on residual limbs within a silicon liner worn by amputees, where dynamic pressure, narrow space, and perspiration can negatively affect sensor performance. Existing commercial sEMG sensors and newly developed sensors are unsuitable due to size and thickness, or susceptible to damage in this environment. In this paper, our sEMG sensors are tailored for amputees wearing sockets, prioritizing breathability, durability, and reliable recording performance. By employing porous PDMS and Silbione substrates, our design achieves exceptional permeability and adhesive properties. The serpentine electrode pattern and design are optimized to improve stretchability, durability, and effective contact area, resulting in a higher signal-to-noise ratio (SNR) than conventional electrodes. Notably, our proposed sensors wirelessly enable to control of a robotic leg for amputees, demonstrating its practical feasibility and expecting to drive forward neuro-prosthetic control in the clinical research field near future.

Recently, methods for the treatment of chronic diseases and disorders through the modulation of peripheral and autonomic nerves have been proposed. To investigate various treatment methods and results, experiments are being conducted on animals such as rabbits and rat. However the diameter of the targeted nerves is small (several hundred μm) and it is difficult to modulate small nerves. Therefore, a neural interface that is stable, easy to implant into small nerves, and is biocompatible is required. Here, to develop an advanced neural interface, a thiol-ene/acrylate-based shape memory polymer (SMP) was fabricated with a double clip design. This micro-patterned design is able to be implanted on a small branch of the sciatic nerve, as well as the parasympathetic pelvic nerve, using the shape memory effect (SME) near body temperature. Additionally, the IrO₂ coated neural interface was implanted on the common peroneal nerve in order to perform electrical stimulation and electroneurography (ENG) recording. The results demonstrate that the proposed neural interface can be used for the modulation of the peripheral nerve, including the autonomic nerve, towards bioelectronic medicine.