Optogenetic studies of the peripheral nervous system and spinal cord are enabled by soft, wirelessly powered biocompatible devices. Optogenetics allows rapid, temporally specific control of neuronal activity by targeted expression and activation of light-sensitive proteins. Implementation typically requires remote light sources and fiber-optic delivery schemes that impose considerable physical constraints on natural behaviors. In this report we bypass these limitations using technologies that combine thin, mechanically soft neural interfaces with fully implantable, stretchable wireless radio power and control systems. The resulting devices achieve optogenetic modulation of the spinal cord and peripheral nervous system. This is demonstrated with two form factors; stretchable film appliqués that interface directly with peripheral nerves, and flexible filaments that insert into the narrow confines of the spinal epidural space. These soft, thin devices are minimally invasive, and histological tests suggest they can be used in chronic studies. We demonstrate the power of this technology by modulating peripheral and spinal pain circuitry, providing evidence for the potential widespread use of these devices in research and future clinical applications of optogenetics outside the brain.

Assembling nanocrystal devices: A wide range of materials can be grown as high-quality colloidal nanocrystals, with properties spanning from conductors to semiconductors and insulators. Although these materials have been included in electronic devices, they usually only form a single component within the device. Choi et al. took a variety of solution-processable colloidal nanocrystals to form all of the device components. Through the development of the right materials, interfaces, and processing steps, they constructed an all-colloid field effect transistor. Science , this issue p. 205