Development of novel pH image sensor for in-vivo apprication

A needle type pH image sensor with 32×128 pixels for in-vivo application was developed. The pixel pitch of the sensor is 23 μm and the time resolution is about 20msec (50flame/sec). To insert in the brain of a mouse, the geometry was modified to needle structure with 1.76×11.46 mm and 100 μm thickness. The needle type pH image sensor was covered by parylene C with a thickness of 4 μm without pH sensing area for waterproofing. In this study, we observed dynamic change of pH immediately after insert the sensor into cortex. Interestingly, we found that cortical pH is depth-dependent. Furthermore, pH in superficial layer was decreased by pharmacological manipulation and sensory stimulation whereas pH in deep layer increased. Finally, we found that spike-like responses are caused by pharmacological and sensory stimulation.