A polycrystalline diamond-based, hybrid neural interfacing probe for optogenetics

This paper reports a hybrid optoelectronic neural interfacing probe, combining micro-scale light emitting diode (μLED) and microelectrodes on a polycrystalline diamond (PCD) substrate for optogenetic stimulation and electrical recording of neural activity. PCD has superior thermal conductivity (up to 1800 Wm^-1K^-1) [1], which allows rapid dissipation of localized LED heat to a larger area to improve heat exchange with surrounding perfused tissues, and thus significantly reduce the risk of thermal damage to nerve tissue. During repetitive stimulation with 100ms and 1Hz pulses, the maximum rise in surface temperature of the PCD probe is less than 1 °C, which is ~90% lower than that of a polymer-based probe. A PCD based probe with two stimulating sites and four recording sites was fabricated. The capacity of the probe for neural stimulation and recording has also been demonstrated in vivo by successfully observing light evoked action potentials.