biomimetic_nanostructured_surfaces.doc-HarvardUniversity.docVIP

Biomimetic Nanostructured Surfaces with Designer Mechanics and Geometry for Broad Applications Alexander K Epstein and Joanna Aizenberg Harvard University School of Engineering and Applied Sciences 29 Oxford Street, Cambridge, MA, U.S.A. ABSTRACT A powerful fabrication platform for a wide range of biomimetic, high-aspect-ratio nanostructured surfaces is introduced. The principles of soft lithography are extended into a double-mold replication process, whereby a master topography is mapped onto an elastomeric inverse mold and replicated in arbitrary multiple material and stiffness gradients, and an array of modified geometries. Control of geometry via deformation of the inverse mold and control of stiffness via prepolymer mixing are discussed. New capabilities enabled by our approach include biomimetic actuation/sensor arrays with programmable biases, precisely tunable mechanical and geometric properties for optical or wetting applications, and flexible curved substrates. Indeed, flexibly anchored ciliary high-aspect-ratio nanostructures are now possible, and a proof-of-principle is described. INTRODUCTION Biology abounds with examples of functional structures, whose properties are unmatched in today’s synthetic materials. Key features of biological structures include their dynamic nature, responsive behavior and often multi-functionality, which all comprise goals for the next-generation of smart artificial materials. Organisms and plants use sophisticated design strategies to achieve superior mechanical, optical, adhesive, self-cleaning, actuation and sensing capabilities. [1–9] A common feature of these largely unrelated designs is the use of fibers and high-aspect-ratio nano- and micro-structures. Synthetic actuation/sensing at the sub-micron scale remains a challenging goal. Sensor arrays inspired by fish skin [10] and actuator arrays mimicking cilia still lack key features of selectivity, tunable geometry and sensitivity. In the current study we use a