Self‐folding Materials and Devices

by Prof. David Gracias (The Johns Hopkins University, USA)

Thursday, December 22, 2011 from 14:30 to 15:30 (Asia/Kolkata)
at Colaba Campus ( AG-66 (Lecture Theatre) )

TIFR, Colaba Mumbai 400005

Description

Nature is the master of engineering across a wide range of length scales from the nano to the macro. In contrast, while humans are good at constructing three dimensional (3D) macroscale devices and machines, we face considerable challenges at sub‐millimeter length scales. At these small sizes, while engineers have learned how to define complex devices such as computer chips, they utilize methods that are inherently two dimensional (2D).

Self‐assembly is a biologically inspired methodology that seeks to construct functional materials and devices using precursors that interact with each other via physical or chemical forces. Self‐folding refers to self‐assembly processes wherein planar structures curve or fold up spontaneously, typically when released from a substrate or exposed to specific stimuli. Many structures in nature such as proteins, leaves and tissues are folded. Self‐folding is also technologically important since it can transform precisely patterned 2D micro and nanostructures into functional 3D materials and devices.

In this talk, I will describe static and reconfigurable self‐folding of 3D micro and nanostructures such as polyhedra, large bi‐directionally folded sheets and wireless microsurgical tools. In our work, self‐folding is driven by heating or when exposed to specific chemicals (microchemomechanical systems). The process can be likened to origami, except curvature and folds are achieved in a “hands‐free” manner and without any active control over folding pathways. I will discuss how stresses in thin films can be manipulated to engineer self‐folding forces and pathways, as well as applications of self‐folded materials and devices in optics, electronics and medicine.