Neuroprosthetics containing multi-contact electrodes that can substitute certain nerve functionalities may be able to restore amputees' sense of touch and help the paralyzed walk again by stimulating their spinal cords and silencing the nerve activity of people suffering from chronic pain. Stimulating nerves at the right place and the right time is essential for implementing effective treatments, but still a challenge due to implants' inability to 
Schematic of the nerve-on-a-chip platform. Source: EPFLrecord neural activity precisely.
To achieve a more precise nerve stimulation modality, researchers from Switzerland’s Ecole Polytechnique Fédérale de Lausanne (EPFL) engineered a nerve-on-a-chip platform to stimulate and record from explanted nerve fibers, just as an implanted neuroprosthetic would. The system includes microchannels embedded with electrodes and explanted nerve fibers that replicate the architecture and functioning of in vivo tissue. By modulating and rapidly recording nerve activity with a high signal-to-noise ratio, the miniaturized electronic platform broadens the scope for using chips to improve neuroprosthetic designs.
The chip can record the activity of individual nerve cells and was used to test a photothermic method for inhibiting neural activity. P3HT:PCBM, a photothermic semiconducting polymer, was deposited on some of the chip's electrodes. As the polymer heats up on exposure to light, the sensitive electrodes measured a difference in activity between the different explanted nerve fibers. The activity of the thinnest fibers, the sensory neurons that cause pain, was observed to be blocked.
The researchers will next use the polymer in an implant placed around a nerve to monitor the neural inhibition effect in vivo as a possible way to treat chronic pain.
The research has been published in Nature Communications.
