Structuring Nanofibers of SMEC Sheets: A New Approach to Control Self‐Folded Shape by Uniaxial Stretching

Abstract

Shape‐memory elastomer composite (SMEC) sheets, made of a honeycomb structured electrospun poly(ε‐caprolactone) (PCL) fiber mat embedded in a silicone (PDMS) elastomer, fold on themselves upon uniaxial traction. The self‐folding of the composite sheet originates from a bi‐layered structure obtained by a simple one‐step impregnation process. Indeed, the impregnation of a structured PCL fiber mat by oily PDMS in a flat Teflon mold leads, after curing, to an asymmetric composite sheet made of one PDMS flat thin layer on the mold side and one rough PDMS/PCL composite layer on the other side due to specific affinities between the three polymers involved. The self‐folded shape of such structured single sheet obtained upon uniaxial stretching and stress release is controlled by the honeycomb pattern orientation versus stretching direction, by the pattern size and by the applied uniaxial stretching stress. High shape recovery and robust shape memory cycling are also demonstrated by dynamic mechanical analysis. This innovative process based on the mat structuration allows a straightforward one‐step fabrication of shape memory sheets, with a wide scope of tunable self‐folded curvatures exhibiting efficient temperature shape recovery.

Mechano‐Activated Shape Morphing of Aluminum–Plastic Laminate Composites

“…[23,24] Despite the qualitative similarity between Figure 1f-h and these older examples, the behavior of stretch-release-induced bending of elastic-plastic composites may be more complex. [2,5,10,12] First, the response of commercial polymer films such as in Figure 1 is often anisotropic such that long strips cut along two orthogonal directions may show distinct bending behaviors suggesting some anisotropy in the polymer due to the manufacturing process. Second, if stretched to a large extent, the sign and direction of the curvature may both flip, [5] an observation that is altogether nonintuitive.…”

“…Beyond our fundamental interest in plasticity effects in layered systems, [ 5–8 ] we are motivated by the potential for origami engineering where shape morphing can be induced in metal–plastic laminates by a simple loading–unloading protocol. Indeed such a stretch–release approach to origami has been explored previously, [ 1,3,4,9–11 ] and Nelson et al [ 3,4 ] have coined the evocative term mechano‐activated shape morphing, a term that we have adopted in the title of this article. Tang et al [ 9 ] showed especially beautiful examples of complex shapes realized by this approach.…”

“…Beyond our fundamental interest in plasticity effects in layered systems, [5][6][7][8] we are motivated by the potential for origami engineering where shape morphing can be induced in metal-plastic laminates by a simple loading-unloading protocol. Indeed such a stretch-release approach to origami has been explored previously, [1,3,4,[9][10][11] and Nelson et al [3,4] have coined the DOI: 10.1002/adem.202301111…”