Implementing and Quantifying the Shape-Memory Effect of Single Polymeric Micro/Nanowires with an Atomic Force Microscope

Abstract

The implementation of shape‐memory effects (SME) in polymeric micro‐ or nano‐objects currently relies on the application of indirect macroscopic manipulation techniques, for example, stretchable molds or phantoms, to ensembles of small objects. Here, we introduce a method capable of the controlled manipulation and SME quantification of individual micro‐ and nano‐objects in analogy to macroscopic thermomechanical test procedures. An atomic force microscope was utilized to address individual electro‐spun poly(ether urethane) (PEU) micro‐ or nanowires freely suspended between two micropillars on a micro‐structured silicon substrate. In this way, programming strains of 10±1% or 21±1% were realized, which could be successfully fixed. An almost complete restoration of the original free‐suspended shape during heating confirmed the excellent shape‐memory performance of the PEU wires. Apparent recovery stresses of σmax,app=1.2±0.1 and 33.3±0.1 MPa were obtained for a single microwire and nanowire, respectively. The universal AFM test platform described here enables the implementation and quantification of a thermomechanically induced function for individual polymeric micro‐ and nanosystems.