Adv. Healthcare Mater. http://doi.org/f3czxp (2015)

Microelectrode arrays composed of multiple silicon needles are used as penetrating devices to record brain electrical activity in vivo. Long and ultrathin needles are required to reach deeper regions in the brain while minimizing penetration-induced tissue damage; however, an increased aspect ratio reduces the stiffness of the needle, which may break during the implantation procedure. Now, Satoshi Yagi and colleagues show that a bioresorbable silk layer deposited at the base of 650-μm-long, 5-μm-thick silicon needles acts as a temporary reinforcement that allows the devices to pierce the brain of a mouse without buckling or fracturing. Once in contact with the biological tissues, the silk base dissolves allowing the needles to penetrate completely. With respect to previous approaches proposing coating of the full microelectrode array with bioresorbable materials, this strategy does not increase the diameter of the needles thus minimizing the invasiveness of the devices. The researchers suggest that this method can be used to implant recording and stimulating electrodes, as well as hollow microneedles for drug delivery.