Abstract
Muscle function loss is characterized as abnormal or completely lost muscle capabilities, and it can result from neurological disorders or nerve injuries. The currently available clinical treatment is to electrically stimulate the diseased muscles. Here, a self‐powered system of a stacked‐layer triboelectric nanogenerator (TENG) and a multiple‐channel epimysial electrode to directly stimulate muscles is demonstrated. Then, the two challenges regarding direct TENG muscle stimulation are further investigated. For the first challenge of improving low‐current TENG stimulation efficiency, it is found that the optimum stimulation efficiency can be achieved by conducting a systematic mapping with a multiple‐channel epimysial electrode. The second challenge is TENG stimulation stability. It is found that the force output generated by TENGs is more stable than using the conventional square wave stimulation and enveloped high frequency stimulation. With modelling and in vivo measurements, it is confirmed that the two factors that account for the stable stimulation using TENGs are the long pulse duration and low current amplitude. The current waveform of TENGs can effectively avoid synchronous motoneuron recruitment at the two stimulation electrodes to reduce force fluctuation. Here, after investigating these two challenges, it is believed that TENG direct muscle stimulation could be used for rehabilitative and therapeutic purpose of muscle function loss treatment.
Highlights
While self-powered triboelectric nanogenerator (TENG) sensors made significant impact to wearable electronics ranging from healthcare, human–machine interface, robotics, gaming, virtual reality, and augmented reality,[33–42] TENG shows great potential to serve as both waveform generator and power supply in the implantable electrical muscle stimulation systems, considering the recent successful demonstrations of direct electrical stimulation on the cells, peripheral nerves, and brain using current output from the TENGs
We demonstrated direct TENG muscle stimulation using a self-powered system of stacked-layer TENG and multiple-channel spiked epimysial electrode
For the first stimulation efficiency challenge, we found TENG stimulation efficiency is affected by electrode configurations and a mapping
Summary
To access the widely distributed motoneurons in the muscle tissue, we used a multiple-channel epimysial electrode. This spiked epimysial electrode is fabricated using microelectromechanical systems process[64] and has five channels, formed by. We used a stacked-layer TENG together with the spiked epimysial electrode as a prototype system to investigate the grand challenges in TENG direct muscle stimulation. Considering that current-controlled waveform is more stable, we characterized the current delivery capability of the stacked-layer TENG. Since the inner impedance of the TENGs falls in several MΩ (5 MΩ for the stacked-layer TENG, as shown, Supporting Information) and the tissue impedance is only around several kΩ, the short-circuit current output of 75 μA (Figure 2b) well characterizes the stacked-layer TENG current delivery capability for in vivo applications.
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