Biomedicine How Heart-Muscle Devices Are Made Devices made of heart tissue could screen drug candidates and be used to power implantable robots. by Kevin Bullis December 18, 2008 Sponsored by Feinberg uses a pipette to apply a protein called fibronectin to a clear polymer stamp patterned with microscopic lines. He presses the stamp onto a silicone-coated coverslip, transferring lines of the protein to the silicone. Then he immerses the coverslip in a solution of heart cells (red liquid). The protein lines direct the growth of heart tissue. Adam Feinberg has made a simple heart-muscle-powered actuator: a strip of polymer that flexes when the muscle contracts. Through a low-powered microscope, the orientation of the muscle tissue is visible near the point where he grips the elastic film with a pair of forceps. Feinberg controls the rate of the contractions by changing the frequency of electronic pulses.