Two m-thick PEE-PPy films are flipping and navigating over a 30°C moist substrate. The large one is 9 cm × 9 cm and the small one is 2 cm × 4 cm. Despite the size difference, these two films flip at a similar frequency. This video relates to a paper that appeared in Jan. 11, 2013, issue of Science, published by AAAS. The paper, by M. Ma at Massachusetts Institute of Technology in Cambridge, MA, and colleagues was titled, "Bio-Inspired Polymer Composite Actuator and Generator Driven by Water Gradients."