High-cycle Fatigue Testing Platform for 1-D Nanomaterials Based on Digital Micromirror Device (DMD)

Description

Despite extensive research into the mechanical properties of one-dimensional (1-D) nanomaterials, such as metallic/semiconductor nanowires and carbon nanotubes, for the past two decades, experimental data on the fatigue behavior (i.e. the changes in properties resulting from cyclic loading) of these 1-D nanostructures have rarely been reported. This is largely due to the critical challenges on performing quantitative mechanical testing on such exceedingly small samples with consistent repeated loading. Recently, MEMS (microelectromechanical systems)-based testing platforms have emerged as powerful and versatile tools to interrogate low-dimensional micro- and nanostructures, and a number of MEMS devices have been successfully developed to investigate the mechanical strength and plastic deformation for various kinds of 1-D nanomaterials. However, the dynamic characterization for important fatigue behavior, which ultimately limits the ability to achieve the full potential of nanowire/nanotubebased devices in numerous engineering applications, especially flexible electronics and bio-integrated electronics, remains highly challenging, mainly due to the inherent limitations of existing MEMS designs. Here, instead of designing a dedicated MEMS device, we propose to adopt a commercially available MEMS product---DMD (Digital Micromirror Device, by Texas Instruments) for the development of a novel nano-fatigue testing platform, and to study the high-cycle fatigue behavior of metallic nanowires and carbon nanotubes.Originally designed for Digital Light Processing (DLP) as a sophisticated light switch, DMD is essentially millions of hinge-mounted microscopic mirrors which can be individually deflected +/- 12 degrees for several thousand times per second (up to 32kHz). Through the electrostatic force attraction, the deflection of each micro mirror can be controlled by changing the binary state of the underlying CMOS memory cell, to realize the cyclic tensile or torsional loading onto the sample. The small footprint of DMD chip also makes it’s capable for “in situ” testing---to perform experiments inside a scanning electron microscope (SEM) for observing the deformation process; on the other hand, by taking advantage of DMD’s own characteristics, it’s possible to monitor fatigue testing status directly by optical projection, without the need of electron microscopes, which may facilitate the study of biomaterials and tissues as well as the environmental effects on fatigue behavior for 1-D nanomaterials. We believe that the implementation of this proposal will not only offer some key insights on fatigue behavior of 1-D nanomaterials, but also stimulate interest among researchers in exploring other potentials in existing MEMS designs, as well as developing even more capable MEMS-based platforms for cross-disciplinary, unconventional engineering and research applications.