(a) Schematic illustration of the octagonal separator. (b) Computer-aided design of the sensor platform containing octagonal separators. Multiple octagonal separators were placed on the center of the square platform. (c) Procedure for cell introduction into the octagonal separator. Collagen with sensor cells was placed on the glass slide, and subsequently, the sensor platform was placed on top to fill each chamber with cell-laden collagen. After incubation to confirm the gelation of collagen, the excess collagen was removed from the device.