Educational pathways through nanoscience: Nitinol as a paradigmatic smart material

We developed an educational path based on nitinol, a shape memory alloy which conveniently exemplifies the smart material concept, i.e., a material that performs a predetermined, reversible action in response to a change in the environment. Nitinol recovers a given shape, changes its resistivity drastically and modifies its elastic properties if subjected to a temperature change in a convenient range. Here, the properties are verified with laboratory protocols appropriate to a high-school environment. Use of mobile electronic devices is also suggested. The collected electrical and mechanical properties are analysed within a didactic path which emphasizes their common physical origin, i.e., the martensitic transition. Moreover, the peculiarities of this solid-to-solid transformation are put in correspondence with the apparently unrelated but more familiar liquid-vapour transition. The relationship with possible applications is emphasized by measuring the efficiency of using a nitinol spring as an actuator.