Researchers from Stanford University developed a wireless device combining optogenetics with wireless technology, paving the way for a new breed of implants.

Optogenetics utilizes light to control brain activity. Traditionally though, light is delivered and nerves are controlled through a fiber optic cable attached to the head of a mouse. Though the headgear carries out the tasks needed, it presented certain challenges, like making it difficult for a mouse to navigate enclosed spaces or burrow under other mice in their cage to sleep. A researcher also has to handle a mouse to attach the headgear before an experiment and this stresses the mouse, potentially affecting outcomes.

Ada Poon is renowned for creating small, wireless implantable devices but she didn't realize how badly her abilities were sought-after in optogenetics until she went to a neural engineering workshop. She met Logan Grosenick at the event and gathered other collaborators through follow-up conversations.

Poon and colleagues want to clarify though that optogenetics only affects nerves that have been particularly prepared to house light-responsive proteins. For this, scientists have to either carefully inject protein DNA-carrying viruses into nerves as thick as dental floss or breed mice to specifically contain light-responsive proteins in certain nerve groups. Just shining a light on neurons will not produce an effect.

The researchers already had a light source but the problem was powering the device without losing power efficiency. As the mouse will be moving around in a behavioral experiment, they needed to track movement to deliver localized power. What other labs had to do is to attach a series of coils with sensors to the mouse's head.

Poon didn't like this idea so they pursued one of hers: using the mouse itself to deliver radio frequency energy. She worked with Yuji Tanabe in Japan to create a chamber that will amplify and store the energy they need to power the device. To prevent the chamber from radiating energy indiscriminately, it was overlaid with a grid with holes smaller than the wavelength of the energy stored inside.

Whenever a mouse moved then, it comes into contact with the energy and energy is drawn in to power the device. This novel method of delivering power allowed the researchers to create a device small enough to be implanted under the skin. It also opens up the possibility of triggering signals in muscles and other organs, which was previously untapped to optogenetics.

According to the researchers, their work may have potential applications for experiments involving mental health disorders, internal organ diseases and movement disorders.

Other authors include: Scott Delp, Karl Deisseroth, Emily Ferenczi, Shrivats Mohan Iyer, Vivien Tsao, John Ho, Alexander Yeh and Kate Montgomery.

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