Extended Data Fig. 4: Irreversible and quasi-reversible actuation of SEAs.
From: Electronically integrated, mass-manufactured, microscopic robots
a, Top: cyclic voltammogram of a titanium–platinum SEA over a large voltage range versus Ag/AgCl, swept at 1 V s−1. Standard features of platinum electrochemistry are observed: hydrogen adsorption and desorption peaks from about −0.5 V to −0.9 V and a broad peak at positive voltages that includes both oxygen-species adsorption and later oxidation of the platinum. When the sweep returns from the oxidation regime, there is an oxide reduction peak at about −0.3 V. Bottom: the curvature of a SEA over the same range, showing strong hysteresis in the platinum oxidation regime. b, Top: cyclic voltammogram for a titanium–platinum SEA, sweep rate 400 mV s−1, over a narrower sweep range, avoiding oxidation of the platinum. We find that the cyclic voltammogram is relatively reversible in both the hydrogen and oxygen adsorption/desorption regimes. Bottom: the curvature of a SEA over the same quasi-reversible range of voltages. We observe two branches of actuation, the hydrogen and oxygen-species adsorption regimes, each with a small amount of hysteresis. All measurements were performed in phosphate-buffered saline solution.
