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Page 12 of 31 Lee et al. Soft Sci 2024;4:38 https://dx.doi.org/10.20517/ss.2024.36

Figure 9. Schematic diagrams of homogeneous elastomer films directly patterned by (A) aligning the polymer network and (B) adjusting
the crosslink density.

method operates at low temperatures below 100 °C and can produce highly ordered sub-10 nm patterns in
under a minute, generating uniform and low-defect patterns that are effective for various BCP
morphologies. Ditte et al. developed a triblock copolymer (TBC) combining poly-diketopyrrolopyrrole-
thienothiophene (PDPP-TT) with PDMS to achieve the low elastic modulus and high charge mobility
[93]
essential for stretchable electronics [Figure 10C]. Through the arrangement of this TBC, they induced
anisotropic charge transport within the elastomer film, leading to performance variations based on the
direction of the electric field and the applied strain. Grazing-incidence wide-angle X-ray scattering
(GIWAXS) analysis revealed that the TBC has an edge-on molecular orientation, aligned perpendicular to
the substrate, which facilitates charge transport pathways parallel to the film surface and enhances electron
mobility.

LCEs consist of rigid liquid crystal (LC) mesogens crosslinked within a polymer network, and the
[94]
orientation of this network is determined by the direction of the LC director . The van der Waals
interactions between the LC directors allow for hierarchical alignment in the thickness direction. Depending
on the anchoring properties, alignment directions, and positional alignment profiles of mechanically or
optically aligned thin films, various geometries such as vertical, horizontal, and twisted configurations can
be designed, making it highly advantageous for inducing multi-directional deformation . Mechanical
[95]
alignment involves physically rubbing the surface of the alignment layer to guide the alignment of LC
directors, providing strong anchoring properties that are effective even for thick films [96,97] . However, it has
limitations in inducing complex spatial alignments. In contrast, optical alignment involves exposing the
alignment layer to specific wavelengths of light, which induces chain cleavage and recombination to provide
directional control [98,99] . By patterning the light source, spatial alignment can be easily controlled, making it
more suitable for complex alignments. Choi et al. developed a LC polymer designed to form a twisted
geometry in the thickness direction and combined it with an azobenzene monomer to create an ultraviolet
[96]
(UV)-responsive LCE strip [Figure 10D]. By exposing the aligned film to light, they induced curvature
deformation in the designed helices and applied this to a soft robot capable of programmable multi-motion.
Ahn et al. applied inhomogeneous stretching and optical alignment techniques during the film fabrication
process to induce patterned molecular orientation, creating LCE films with programmable complex