(141h) Programmable Microfluidic Materials with Controlled Shape, Stiffness and Color

Microfluidic systems for bioanalysis, organic and nanoparticle synthesis have been widely investigated. The potential of microfluidics in other areas of technology, such as making materials with extraordinary adhesion and self-healing properties has only begun to be realized and explored. We will present a class of novel microfluidic materials in the form of flexible sheets that can be solidified on demand by light to acquire specific shapes or that can switch their color. The matrix of these materials is thin sheets of polydimethylsiloxane (PDMS). The microfluidic channel networks embedded in the elastomer are filled with liquid photocurable polymer. The materials formed in this way possess the unique ability to "memorize" and retain user-defined shapes upon illumination. When the microchannel networks are deformed and exposed by UV light, the photoresist inside the channels is solidified and subsequently acts as endoskeleton within the PDMS layer, locking in the programmed shape. The bending and stretching moduli of the materials with solidified endoskeleton increase drastically. The permanent locking in of the shape of light-solidified microfluidic sheets could be used in making instant containers, patches and supports on demand, creating "exoskeletons" for delicate devices, rapid prototyping and multiple other applications. We will also present the results of a technique for making new microfluidic materials that can switch controllably their color and transmittance in the visible and infrared range. Such "chameleon" microfluidic sheets can find applications in smart windows and energy management.