Strain gages are electrical sensors that measure the change in electrical resistance when a device’s shape is deformed. For example, a strain gage at the tip of a endoscopic surgical instrument can determine the force needed to make an incision, and with instantaneous feedback can tell a robotic surgeon in Berlin how hard to press the “scalpel” on the patient in Madrid. This piece reviews the design of such gages which might also be used for implantable brain devices.     MORE