<p><span class="h-card" translate="no"><a href="https://ioc.exchange/@azonenberg" class="u-url mention">@<span>azonenberg</span></a></span> I wonder if there are any photochemical reactions that could be exploited here. Phase change for applying work via pressure would probably be too thermally dependent, but perhaps there might exist an equilibrium reaction whereby the presence of light leads to (or inverts) a separation of two liquids of differing densities, allowing you to use a precisely bouyant float.</p>