Kinetics of enzymatic triggering. Plots of the experimentally measured diameter reduction ratio (D/Dmax) versus time on exposure to a variety of enzymes. The line denotes the average value measured over 5 trials and the shaded region denotes the standard deviation. The curves demonstrate sensitivity to enzyme class. The grippers that use a gelatin based trigger actuated in less than 30 minutes in trypsin, papain and collagenase, actuated in less than an hour in viscozyme, actuated in less than a week by cellulase, and did not actuate in PBS or cell culture media with serum after several months. The grippers with a cellulase biopolymer layer are actuated in less than ten minutes in viscozyme and 1 hour in cellulase. There is some actuation within a month in papain and trypsin; in over a month there is no significant actuation in collagenase, PBS, or media. (PBS and media results are included in the Supporting Figure S5)