This is a basic mockup of one of our creatures bristles. It is driven by a servo motor that responds to pressure input from an FSR. Our creature has three states: Happy, Angry and Neutral.
It starts out in Neutral, with the bristle half-in and half-out. When the FSR is pressed to a certain point, the creature responds positively by fully extending its bristle. If too much pressure is applied, the creature responds negatively by retracting the bristle.
After several seconds of receiving no pressure input, the creature goes back to a neutral state.