Temporally Delayed Deployment of Photo-Responsive Liquid Crystal Polymer Networks Toward Neural Interfaces.

Deployable medical devices are designed to be compact during insertion and expand after surgical placement. Devices such as neural interfaces can leverage deployment to minimize the size of the foreign body cascade near the electrode, potentially improving chronic recording and stimulation performance. To trigger deployment, a stimuli responsive material can be used. However, external stimuli are difficult to supply within tissues. Intrinsic changes upon implantation, such as water uptake, are difficult to control and may lead to device failure. Here, we describe a strategy to deploy small-scale structures into soft tissues after insertion without the need for any stimulus. Photoresponsive liquid crystal networks (LCNs) are crosslinked after self-assembly of monomers and adopt a programmed 3D form at room temperature (RT). The trans-cis isomerization of azobenzene enables the 3D LCN films to be flattened by UV light before insertion and revert to 3D forms over 5 h at body temperature. A film programmed to adopt a cone shape with a diameter of 531 µm can actuate to 53 µm in height. Rigidity of the films enables penetration into and deployment within soft tissues. The described materials could potentially enable self-deployable biomedical devices, including neural interfaces with sub-mm features.