Universal Scaling Law for the Size Effect on Superelasticity at the Nanoscale Promotes the Use of Shape‐Memory Alloys in Stretchable Devices

FUSTER, VALERIA; GÓMEZ-CORTÉS, JOSÉ F.; NÓ, MARÍA L.; SAN JUAN, JOSE M.

Advanced Electronic Materials

WILEY-VCH Verlag GmbH & Co. KGaA

Lugar: Weinheim; Año: 2019 vol. 6 p. 1900741 - 1900741

2199-160X

Shape‐memory alloys (SMAs) are the most stretchable metallic materials thanks to their superelastic behavior associated with the stress‐induced martensitic transformation. This property makes SMAs of potential interest for flexible and wearable electronic technologies, provided that their properties will be retained at small scale. Nanocompression experiments on Cu‐Al‐Be SMA single crystals demonstrate that micro‐ and nanopillars, between 2 µm and 260 nm in diameter, exhibit a reproducible superelastic behavior fully recoverable up to 8% strain, even at the nanoscale. Additionally, these micro‐/nanopillars exhibit a size effect on the critical stress for superelasticity, which dramatically increases for pillars smaller than ≈1 µm in diameter, scaling with a power law of exponent n = −2. The observed size effect agrees with a theoretical model of homogeneous nucleation of martensite at small scale and the universality of this scaling power law for Cu‐based SMAs is proposed. These results open new directions for using SMAs as stretchable conductors and actuating devices in flexible and wearable technologies.