Biomimetic Nanostructured Surfaces with Designer Mechanics and Geometry for Broad Applications
- PDF / 355,619 Bytes
- 7 Pages / 612 x 792 pts (letter) Page_size
- 13 Downloads / 233 Views
1236-SS09-07
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 nextgeneration 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 truly materials approach to develop a low-cost procedure for arbitrarily-designed actuated surfaces with highaspect-ratio nanostructures that are themselves responsive to a variety of stimuli and have a finely tuned geometry and stiffness. We first show how soft lithography fabrication can be extended to control both mechanical and geometric properties of these surface nanostructures. Furthermore, we demonstrate how to fabricate flexibly anchored high-aspect-ratio nanostructures where there exists a stiffness and materials gradient between the nanostructures and the underlying substrate, which represents a critical functional requirement of biological actuated nanostructures and sensors. EXPERIMENTAL DETAILS A square array of silicon nanoposts (height = 8 µm, diameter = 250 nm, pitch = 2 µm) was fabricated using the Bosch process, as described elsewhere. [11,12] The silicon nanopost arrays were treated with an anti-sticking agent (tridecafluoro-1,1,2,2-tetrahydrooctyl)-trichlorosilane (Gelest Inc.) by exposure in a desiccator under vacuum overnight.
Data Loading...
