Silicon optrode array with monolithically integrated SU-8 waveguide and single LED light source.

Area of Science:

• Neuroscience
• Biomedical Engineering
• Optoelectronics

Background:

• Optogenetic neuromodulation requires efficient light delivery systems.
• Existing systems often face challenges with power consumption and light coupling efficiency.
• Silicon optrode arrays are crucial for neural recording.

Purpose of the Study:

• To develop a novel light-emitting diode (LED) and polymer waveguide coupled silicon optrode array.
• To enhance light coupling efficiency and reduce power consumption for wireless optogenetic systems.
• To demonstrate simultaneous optical stimulation and neural signal recording.

Main Methods:

• Fabrication of a lensed waveguide using SU-8 photoresist with a plano-convex lens.
• Integration of a cylindrical lens to focus light in the vertical direction.
• Assembly of a 1x4 optrode array with a 465 nm LED and iridium oxide (IrO2) electroplated recording electrodes.

Main Results:

• The integrated lens system increased light coupling efficiency by 6.7 dB (cylindrical lens) and 6.6 dB (plano-convex lens).
• The optrode array delivered a light intensity of approximately 2.7 mW/mm² at the waveguide outlet.
• The iridium oxide recording electrodes exhibited an average impedance of 43.6 kΩ.

Conclusions:

• The developed LED and SU-8 waveguide coupled silicon optrode array successfully demonstrated in-vivo optical stimulation and neural recording in the hippocampus (CA1 and CA2 regions).
• The system's design facilitates high light coupling efficiency and low power consumption, suitable for wireless applications.