Wireless Optogenetic Illuminator
I built a wireless widefield optogenetic illuminator that is simple, cheap, lightweight, and remotely triggered. Read on for details, including how to build it yourself. Also looking for feedback and ideas about how we could use this thing!
The use case: You want to illuminate a large (>1 sq mm) brain area wirelessly and minimally invasively. Implanted optic fibers (~0.2 mm diameter) too focal for big regions, and besides optic fibers and power cables are bulky and tangly for freely moving.
Solution-- for a light source, attach a small, super-bright LED outside the skull (incurring some loss). For $0.60, this one does max 22 mW blue light at 34 mA. Light comes out in an 18 deg cone, so illuminates a 0.63 mm circle at 2 mm distance.
Power source: Li-Po batteries are high-current, high-capacity, and super small. (That's why they're commonly used for drones.) Here's the smallest one I could find. 1.1 grams, can source 40 mA continuously for 1 h between recharges, $3.50.
Wireless trigger: Basically the same tech as TV remotes. You tell an Arduino to pulse an infrared LED, which triggers an IR receiver on the head to switch on the blue LED. Latency <1 ms. Can do arbitrary stim patterns (40 Hz train, continuous, etc).
Circuit board: I designed this compact PCB and ordered it from OSH Park, $2.20 for three. You can order it too. (Not an ad.. I don't make any profit off this.)
Here's what it looks like all assembled. Two LEDs on the bottom (for bilateral stim), the battery is the silver rectangle. Most of the weight (4 g) is connectors, which could be optimized away in a future version.
Here it goes! The clear LED is the transmitter that triggers it to start pulsing. It doesn't have to be that close... no problems triggering from >50 cm away. Total cost (excluding Arduino) is <$15. Assemble with basic soldering skills in ~1 hr. You can build it!