Multiscale tailoring of helical lattice systems for bespoke thermoelasticity

(Meta-)Materials, e.g. functional or architectured materials that change shape in response to external stimuli, often do so by exploiting solid–solid phase transitions or concerted elastic deformations. For the resulting system to be effective the (meta-)material needs to have desirable and tunable properties at length scales sufficiently small that desirable continuum behaviour of the resulting component is obtained. Developing such (meta-)materials has proven to be an endeavour which requires considerable expertise in science, engineering and mathematics. Here, we pursue an alternative approach where the design for functionality is integrated across multiple length scales in the system. We demonstrate this approach by designing and prototyping helical lattices that act as one-dimensional thermoelastic materials with unusual properties such as negative thermal expansivity—with magnitude far exceeding the most extreme values reported in the literature—and zero-hysteresis shape memory. Our strategy is independent of characteristic length scale, allowing us to design behaviour across a range of dimensions.