To reveal the underlying mechanism of infrared neural stimulation (INS) in the deep tissue properly, we present the design, the fabrication scheme and functional testing of a novel, multimodal optrode for future INS experiments in vivo. Three modalities – electrophysiological recording, thermal measurement and delivery of infrared light – were integrated using silicon MEMS technology. Due to the monolithically integrated functionalities, a single probe is sufficient to determine safe stimulation parameters in vivo. As far as we know, this is the first planar, multimodal optrode designed for INS studies in the deep tissue.

The average overall efficiency of the microoptical system delivering the infrared light at chip-scale is measured as 32.04 ± 4.10 %, while the max. efficiency in packaged form is 41.5 ± 3.29 %. The average beam spot size at the probe tip is 0.024 ± 0.006 mm2. The temperature coefficient of resistance of the integrated thermal sensor monitoring the change in background temperature is 2636 ± 75 ppm/°C. The average impedance of the electrophysiological recording sites is 1031 ± 95 kΩ.

More details in the following papers:

M. Kiss, P. Földesy, Z. Fekete: Optimization of a Michigan-type silicon microprobe for infrared neural stimulation, Sensors & Actuators B-Chemical 224 (2016) 676-682

ÁC Horváth, ÖC Boros, Ö Sepsi, S Beleznai, P Koppa, Z Fekete: A multimodal microtool for spatially controlled infrared neural stimulation in the deep brain tissue, Sensors & Actuators B-Chemical 263 (2018) 77-86