Novel flat interface nerve electrode (FINE) design by electrically driven shape memory alloys (SMAs)

Flat Interface Nerve Electrodes (FINE) reshape the nerve, which results in an oval geometry and causes the fascicles to be arranged on an axis. In this way, they can provide selectivity at the fascicle level without penetrating the nerve. However, the constant pressure exerted on the nerve during the reshaping process causes nerve damage. Therefore, a dynamic design is required to apply the required force for shaping the nerve when excitation or receiving signal is necessary. The aim of this study is to design a dynamic FINE that can apply gradual pressure on the nerve using shape memory alloys (SMA). In this study, the actuation mechanism that will apply pressure on the nerve is provided with an SMA shaped as a spring. The main frame of the electrode was fabricated with a 3D printer. Electrode contacts were produced with chromium and gold coated with PVD technique on polyimide. The overall design performance was evaluated by a forcemeter. As a result of driving the actuator with various current values, it has been proved that it can perform gradual and controlled compression. In addition, the actuator can produce up to 0.7 N force. This demonstrates that this design can be used in the manufacture of an electrode capable of gradual compression, as well as in a system designed to cause controlled damage to the nerves.