A new surface engineering technique has been found that will extend the reach of shape memory alloys to new application areas not previously contemplated for these remarkable materials. We have discovered a technique whereby a metallic surface can be made to undergo a thermally-driven transition between an optical flat (when cool), to a highly non-planar surface on warming. This project will demonstrate that Surface Form Memory (SFM) can operate with the high energy density normally associated with shape-memory (>106 J-m-3). If so, such ?high-authority? SFM would enable a variety of novel applications, from variable friction surfaces, to MEMS devices and nano-scale assembly tools. The method we use to obtain SFM involves spherical or cylindrical indentation followed by surface planarization. This indent-planarization technique relies on the discovery that a spherical indent made in martensitic NiTi induces a pronounced shape-memory training effect, leading to two-way shape memory (TWSME). This causes shape-strains to occur cyclically on both heating and cooling. This cyclic depth change is converted to a much more radical change in surface form by the planarization step, in which the surface is carefully ground just enough to render the initial indent invisible. What had been a simple change in indent depth is thereby converted to a transition from a flat surface to one exhibiting a pronounced protrusion. We will explore low-cost methods for producing wide-area surface treatments, and evaluate ideas for the fabrication of tribodynamic surfaces and other components using indentation-planarization methods. In particular, we propose a proof-of-concept demonstration of surfaces capable of very large thermally driven changes in friction coefficient.
