Fabrication of PAAm Hydrogel-Coated Nitinol Wire Coil: All the chemicals were purchased from Sigma-Aldrich (St. Louis, Missouri, USA) and used as received. Milli-Q water was used unless otherwise stated. The PAAm hydrogel-coated Nitinol wire coil was fabricated by wrapping the hydrogel with a thin long channel in the middle onto the coiled-shaped Nitinol wire. First, prepare a pre-solution for hydrogel. Briefly, 0.5331 g of acrylamide (AAm) as monomer, 1.156 mg (0.1mol% of AAm) of  N,N′-Methylenebis(acrylamide) (BIS) as crosslinker, and 13.5 mg of potassium persulfate (KPS) as initiator. Add DI water to afford a 2.5 mL solution mixture for later use. This formula was chosen based on many trails. The as prepared hydrogels are strong so they don’t break easily but still have decent amount of water content. Also the hydrogels won’t keep swelling and become too bulky and hinder the movement of the Nitinol. To prepare the long hydrogel with a thin channel inside, we used a commercially available fishing thread (Beadalon Supplemax JNX0.25W-F, Coatesville, Pennsylvania, USA) with 0.01 inch diameter as a template. A plastic tube with a 3.20 mm inner diameter was used. We horizontally clamped the plastic tube, put the fishing thread inside and fixed the two ends onto monkey bars. Then we pulled the thread to give it a bit tension to make sure it’s straight inside the tube. The position of the tube and the thread was carefully adjusted so that the thread is going through the centre of the tube (Figure S9). Take 20 μL N,N,N′,N′-Tetramethyl ethylenediamine (TEMED) as an accelerator and mix with the prepared pre-solution. Take some solution using a syringe and slowly inject it into the tube. After polymerization is completed and the hydrogel formed, slowly pull the thread to remove the hydrogel out of the tube. Then gently remove the thread inside which should leave a vacant channel inside. Lastly, slowly slide the Nitinol wire into the hydrogel through the channel.