Swimmer Ariana Kukors presses her fingers into a device built to measure the force she generates with her freestyle kick. (She doesn't hold on to anything.) The red vertical line shows the amount of force at a point in time. Kukors's kick is strong and consistent, which is why the wave signal generally has the same amplitude throughout the recording.
Each white square is a polymer nano pen. When the pen tips make contact with a surface, the amount of light that they reflect increases, allowing for easy monitoring of the writing process.
Massachusetts Institute of Technology