A Self-powered Neural Stimulator Based on Programmable Triboelectric Nanogenerators.

Modulation of peripheral nerve is an emerging field for neuroprosthesis and bioelectronic medicine. With the developing neural interfacing technology that directly communicates with peripheral nerves, several powering schemes have been investigated for long-term use of implantable devices such as wireless and conversion of human body energy. But due to the limitations such as energy conversion efficiency and complexity, none of these methods can fully replace the current battery-based neuroprosthetic systems. This study proposes a new scheme based on programmable triboelectric nanogenerators for self-powered neural stimulations. The device can generate current pulses of more than 100 V by slightly shaking the device. The capability of neural stimulation is validated by sciatic nerve stimulation. Furthermore, the shaking frequency can control the measured kicking force of the rat leg. This prototype can be further minimized and optimized for a fully implantable self-powered/wireless neuroprosthetic system.

The effect of the subthreshold oscillation induced by the neurons' resonance upon the electrical stimulation-dependent instability.

Repetitive electrical nerve stimulation can induce a long-lasting perturbation of the axon's membrane potential, resulting in unstable stimulus-response relationships. Despite being observed in electrophysiology, the precise mechanism underlying electrical stimulation-dependent (ES-dependent) instability is still an open question. This study proposes a model to reveal a facet of this problem: how threshold fluctuation affects electrical nerve stimulations. This study proposes a new method based on a Circuit-Probability theory (C-P theory) to reveal the interlinkages between the subthreshold oscillation induced by neurons' resonance and ES-dependent instability of neural response. Supported by in-vivo studies, this new model predicts several key characteristics of ES-dependent instability and proposes a stimulation method to minimize the instability. This model provides a powerful tool to improve our understanding of the interaction between the external electric field and the complexity of the biophysical characteristics of axons.

A physical perspective to understand myelin II: The physical origin of myelin development.

The physical principle of myelin development is obtained from our previous study by explaining Peter's quadrant mystery: an externally applied negative and positive E-field can promote and inhibit the growth of the inner tongue of the myelin sheath, respectively. In this study, this principle is considered as a fundamental hypothesis, named Hypothesis-E, to explain more phenomena about myelin development systematically. Specifically, the g-ratio and the fate of the Schwann cell's differentiation are explained in terms of the E-field. Moreover, an experiment is proposed to validate this theory.

A physical perspective to understand myelin. I. A physical answer to Peter's quadrant mystery.

In the development of oligodendrocytes in the central nervous systems, the inner and outer tongue of the myelin sheath tend to be located within the same quadrant, which was named as Peters quadrant mystery. In this study, we conduct in silico investigations to explore the possible mechanisms underlying the Peters quadrant mystery. A biophysically detailed model of oligodendrocytes was used to simulate the effect of the actional potential-induced electric field across the myelin sheath. Our simulation suggests that the paranodal channel connecting the inner and outer tongue forms a low impedance route, inducing two high-current zones at the area around the inner and outer tongue. When the inner tongue and outer tongue are located within the same quadrant, the interaction of these two high-current-zones will induce a maximum amplitude and a polarity reverse of the voltage upon the inner tongue, resulting in the same quadrant phenomenon. This model indicates that the growth of myelin follows a simple principle: an external negative or positive E-field can promote or inhibit the growth of the inner tongue, respectively.