Rings of Hydrogel Fabricated by a Micro-Transfer Technique

Microgel rings have been fabricated on a glass surface by a micro-transfer technique. The polymer melt is transferred to the substrate surface in a confined space with a picoliter volume along the boundary of the polymeric stamp. The surface of the polymer features is smoothened by surface tension in an annealing cycle, which results in isotropic rings. After cross-linking, the microgels respond swiftly when immersed in water. Asymmetric rings are also obtained by tilting the substrate. The microgels can detach from the substrate to form a suspension of the rings. Conjugated rings have also been fabricated by supplementing functional molecules into the poly(ethylene glycol) network.