Fabrication of a novel laser-processed NiTi shape memory microgripper with enhanced thermomechanical functionality

Abstract

The thermomechanical properties of nickel-titanium shape memory alloys have sparked significant research efforts seeking to exploit their exotic capabilities. Until recently, the performance capabilities of nickel-titanium devices have been inhibited by the retention of only one thermomechanical response. In this article, the application of a novel laser-processing technique is demonstrated to create a monolithic self-positioning nickel-titanium shape memory microgripper. Device actuation and gripping maneuvers were achieved by thermally activating processed material regions which possessed unique phase transformation onset temperatures and thermomechanical recovery characteristics. The existence of each thermomechanical material domain was confirmed through differential scanning calorimetry analysis. Independent thermomechanical recoveries of each embedded shape memory were captured using tensile testing methods. Deployment of each embedded shape memory was achieved using resistive heating, and in situ resistivity measurements were used to monitor progressive phase transformations.

Effect of indentation temperature on nickel-titanium indentation-induced two-way shape-memory surfaces

“…In the solutionized state, both the increased transformation temperatures and the removal of the R-Phase can be attributed to the removal of some of the deformation substructure via the heat treatment process. Cold working has been shown to influence the transition temperatures of NiTi lowering the transformation temperatures (Gibkes et al 2004;Daly et al 2012;Lin et al 1991). Ultimately, the relatively large grain size and more importantly the low dislocation density of the solutionized microstructure is much less complicated than the as-received, and therefore a better choice of this study.…”

Surface characterizations of laser modified biomedical grade NiTi shape memory alloys

“…The ability to precisely and rapidly tune the local material properties, opposed to traditional inaccurate and slow bulk processes, make lasers excellent candidates for SMA processing. For example technologies such as, laser induced vaporization [14][15][16][17][18][19] and local laser annealing [20], have shown great potential to revolutionize the fabrication and design of devices. In these novel laser technologies, rapid local changes in microstructure and/or chemical composition have been shown to effectively fine tune both the pseudoelastic and shape memory properties of NiTi SMAs.…”

A review of micro-devices assembly techniques and technology

“…• Finite-element simulations for stress and strain profile evaluation Kohl et al [16] • Gripping devices mounted between substrates • Photosensor used to identify the optical properties [20] • Monolithic self-positioning NiTi shape memory micro-gripper • Nd:YAG laser system used to process NiTi wire • Resistive heating measurements used to monitor thermal actuation • Used for micro-manipulation automatically transfer individual silicon nanowires from their growth substrate to a MEMS device.…”

“…Shape memory alloy (SMA) materials have been used by several researchers to design gripping mechanisms for manipulation of micro-parts [15][16][17][18][19][20]. Their designs employed SMA wires, thin sheets, and films.…”

“…In order to manipulate objects with varying sizes, a high range to length ratio was maintained in the design; the SMA acted as a self-sensing device in order to reduce additional sensors while providing the force feedback to the controller. Daly et al [20] introduced the fabrication of a novel self-positioning NiTi micro-gripper using laser processing with multiple memory materials. Three material domains were considered as the active components of this micro-gripper.…”