An implantable and fully integrated complementary metal–oxide semiconductor device for in vivo neural imaging and electrical interfacing with the mouse hippocampus

We present a technique for in vivo imaging and electrical interface deep inside the mouse brain using a single complementary metal–oxide semiconductor (CMOS) sensor. In this work, we have developed a device which incorporates an imaging array, electrodes, illumination light source and chemical delivery needle. The device encompasses the functionalities for fluorescence imaging and electrophysiological experiments simultaneously. Micro-electro-mechanical systems (MEMS) microfabrication technique is used to post-process the CMOS sensor chip. Integration of light emitting diodes (LEDs) for illumination and formation of on-chip platinum electrodes for electrical interface with neurons complete the packaged device. Using the device, we performed fluorescence imaging and electrophysiological experiments inside the mouse brain. We have successfully induced synaptic response when the Schaffer-collateral pathway of the mouse hippocampus was stimulated using the on-chip Pt electrodes with current intensities from 200 μA to 1 mA. Furthermore, we have verified empirically that this technique has minimal effect on the hippocampus.