A 10×17 mm poly(vinylidene fluoride) (PVDF) piezoelectric sensor from MEAS was used to measure the force of the impacts. The voltage output from the sensor was read directly using a National Instruments USB-6003 data aqcuisition device recoridng at 10 kHz. A 1 MΩ resistor was used to protect the device from over voltage damage. Typically, a piezoelectric sensor begins to discharge its voltage rapidly after being strained and is not capable of providing steady state measurements. However, the short time scales of the impacts (less than 15 ms) makes the piezoelectric sensor suitable for measuring the force of these impacts. Therefore, we decided to use voltage to characterize the relative change of the force during impact tests. The piezoelectric sensor was fixed to a stiff table. The soft gel and protection stuctures were then attached using silicone grease. This grease provides the necessary adhesion while allowing the soft gel to freely deform under impact.