Compact silicon-based optrode with integrated laser diode chips, SU-8 waveguides and platinum electrodes for optogenetic applications

Abstract

We report on a compact optrode, i.e. a MEMS-based, invasive, bidirectional neural interface allowing to control neural activity using light while neural signals are recorded nearby. The optrode consists of a silicon (Si) base carrying two pairs of bare laser diodes (LDs) emitting at 650 nm and of two 8 mm-long, 250 µm-wide and down to 50 µm-thick shanks extending from the base. Each LD is efficiently coupled to one of four 15 or 20 µm-wide and 13 µm-high SU-8 waveguides (WGs) running in pairs along the shanks. In addition, each shank comprises four 20 µm-diameter platinum electrodes for neural recording near the WG end facets. After encapsulation of the LDs with a Si cover chip blocking stray light and protecting the LDs from the harsh environment to which the probe is destined, the compact base measures only 4 × 4 × 0.43 mm 3 . The time averaged radiant emittance at the WG end facet is 96.9 mW mm −2 for an LD current of 35 mA at a duty cycle of 5%. The absolute electrode impedance at 1 kHz is 1.54 ± 0.06 MΩ. Using infrared thermography, the temperature increase of the probe during LD operation was determined to be about 1 K under neuroscientifically relevant operating conditions.

Microfabricated Probes for Studying Brain Chemistry: A Review

“…The micron‐scale dimensions possible through microfabrication techniques can also reduce the likelihood of tissue damage. One approach involved fabrication and integration of bare laser diode chips (emitting at 650 nm) with a silicon neural probe . The diode chips were directly coupled to SU‐8 waveguides embedded on the probe shank, resulting in a compact packaged device.…”

“…One approach involved fabrication and integration of bare laser diode chips (emitting at 650 nm) with as ilicon neural probe. [202,203] The diode chips were directly coupled to SU-8 waveguides embedded on the probe shank, resulting in ac ompact packaged device. This A) Neuralp robe with an oxynitride waveguide and iridium electrodes.…”

Artifact-free, high-temporal-resolution in vivo opto-electrophysiology with microLED optoelectrodes

“…The combination of genetic engineering-assisted optical stimulation and massively parallel electrical recording of neuronal activities (opto-electrophysiology) is a promising tool for studying neuronal circuits in behaving animals 1 . A number of devices [2][3][4][5][6][7][8][9][10][11] have been introduced for the past few years for in vivo opto-electrophysiology. For high-resolution in vivo opto-electrophysiology, a micromachined silicon multi-electrode-array structure also known as the Michigan Probe 12,13 has been widely utilized [6][7][8][9][10][11] .…”

Hybrid intracerebral probe with integrated bare LED chips for optogenetic studies

“…In order to get rid of the relatively large diode housing, other groups have integrated bare laser diode chips onto neural probes containing integrated optical waveguides (Kampasi et al 2016;Schwaerzle et al 2017). These approaches enable the all-electrical control of the optical probes.…”