High Performance Shape Memory Effect Mini Device Realized by Femtosecond Laser Cutting

After the discovery of the high performance shape memory effect (HP SME) [1] the thermal cycling of the stress induced martensite SIM opens to manufacturing of a new class of SMA smart actuators with extremely high stresses values (up to 1 GPa). Basically, when the martensite is stress induced from austenitic material, the material itself becomes an actuator that can be activated by heating/cooling cycles. Again, if the “SIM is localized” into an austenite matrix, you have a “localized actuator” that can generate a force to all the device. The latter condition opens new prospective in the field of meso and micro scale smart actuators.

In this work a superelastic NiTinol thin sheet was used for realizing a diamond like actuators. Diamond like shape was chosen for assuring localization of SIM in certain parts of the device. Femtosecond wave laser source was used for vaporization cutting of the samples (with truss about 100 microns wide). Stress strain properties were measured in temperature range 20-100 °C and thermal loops under constant load of the HP SME actuators were measured by DMTA analyzer. Fatigue tests of HP SME diamond confirm lifetime performances according to the traditional superelastic material ones.  Finally, modelling of diamond like response under operating HP SME is also reported.

[1] Casati, M. Vedani, A. Tuissi, Thermal cycling of stress induced martensite for High Performance Shape Memory Effect,  Scripta Materialia (80) 13-16 (2014)