Fabrication of PDMS Fish Fins: SYLGARD™ 184 Silicone Elastomer Kit from Dow Inc. (Midland, Michigan, USA) was purchased from Sigma-Aldrich. Mix polymeric base and curing agent at 10:1 ratio. Add some glitter powder (purchased from Dollarama, Montreal, Québec, Canada) and some crystal violet (Sigma Aldrich) for easy visualization under water. Mix well and pour the mixture into a large Petri dish. Put the Petri dish on a heating plate overnight at 65 ℃. Cut a few 3 mm wide plastic strips from a piece of transparency film (3M PP2950, Saint Paul, Minnesota, USA). Place the strips onto the PDMS and pour another layer of PDMS pre-solution and cure overnight similar to previous steps. Cut the cured PDMS sheet into the fish fin shape. Attach the final fish fins onto the two ends of the bistable metal strip using superglue.