Electrochemically Mutable Soft Metasurfaces for Light Manipulation

Active optical metasurfaces, capable of dynamically manipulating light in ultra-thin form factors, enable novel interfaces between humans and technology. Miniaturized implantable devices for light delivery open new applications in biophotonics, including minimally invasive sensing, endoscopic imaging, and optogenetic stimulation. The next generation of human-photonic interfaces will require mechanically adaptive, minimally invasive devices that can dynamically manipulate the shape of optical wavefronts and their spectral properties. In such interfaces, soft materials bring many advantages based on their flexibility, compliance, and large stimuli-driven responses.<br/> <br/>Here, we realise electrochemically-mutable, soft (EMuS) metasurfaces that capitalise on the swelling of soft conducting polymers to alter the shape and associated resonant response of metasurface elements. Previous approaches to dynamic metasurfaces that rely on index-tuning of materials are fundamentally constrained by Kramers-Kronig relations, which prescribe that significant tuning (i.e. index changes) naturally comes with notable absorptive losses. By leveraging the deformability of soft materials to modulate geometry we circumvent these limitations, allowing for effective, low-loss phase tuning. Using the commercial polymer, PEDOT:PSS, we demonstrate dynamic, high-resolution color-tuning and high-diffraction-efficiency (&gt;19%) beamsteering devices that operate at CMOS compatible voltages (~1.5V). Our devices can be realised as ultra-thin, sub-micron coatings, and provide a building block for a new generation of active opto-electronic devices amenable for integration with the human body, potentially enabling new applications in implantable light guiding and bio-imaging.