Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


Title: Movement with light: Photoresponsive shape morphing of printed liquid crystal elastomers
Soft machines will require soft materials that exhibit a rich diversity of functionality, including shape morphing and photoresponsivity. The combination of these functionalities enables useful behaviors in soft machines that can be further developed by synthesizing materials that exhibit localized responsivity. Localized responsivity of liquid crystal elastomers (LCEs), which are soft materials that exhibit shape morphing, can be enabled by formulating composite inks for direct ink writing (DIW). Gold nanorods (AuNRs) can be added to LCEs to enable photothermal shape change upon absorption of light through a localized surface plasmon resonance. We compared LCE formulations, focusing on their amenability for printing by DIW and the photoresponsivity of AuNRs. The local responsivity of different three-dimensional architectures enabled soft machines that could oscillate, crawl, roll, transport mass, and display other unique modes of actuation and motion in response to light, making these promising functional materials for advanced applications.  more » « less
Award ID(s):
2011754
PAR ID:
10500511
Author(s) / Creator(s):
; ; ; ; ; ; ; ; ; ; ; ;
Publisher / Repository:
Cell Press
Date Published:
Journal Name:
Matter
Volume:
7
Issue:
3
ISSN:
2590-2385
Page Range / eLocation ID:
1207 to 1229
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; (, Small)
    Liquid crystalline elastomers (LCEs) are soft materials that associate order and deformation. Upon deformation, mechanically induced changes order affect entropy and can produce a caloric output (elastocaloric). Elastocaloric effects in materials continue to be considered for functional use as solid state refrigerants. Prior elastocaloric investigations of LCEs and related materials have measured ≈2 °C temperature changes upon deformation (100% strain). Here, the elastocaloric response of LCEs is explored that are prepared with a subambient nematic to isotropic transition temperature. These materials are referred as “isotropic” liquid crystalline elastomers. The LCEs are prepared by a two‐step thiol‐Michael/thiol‐ene reaction. This polymer network chemistry enhances elastic recovery and reduces hysteresis compared to acrylate‐based chemistries. The LCEs exhibit appreciable elastocaloric temperature changes upon deformation and recovery (> ± 3 °C, total ΔTof 6 °C) to deformation driven by minimal force (<< 1 MPa). Notably, the strong association of deformation and order and the resulting temperature change attained at low force achieves a responsivity of 14 °C MPa−1which is seven times greater than natural rubber. 
    more » « less
  2. ; ; ; ; ; ; ; (, Nature Communications)
    Liquid crystal elastomers (LCEs) offer significant promise as soft actuator materials, but their potential has not yet been fully explored for 4D printing applications. Most existing studies rely on extrusion-based printing methods, which offer limited resolution and impose constraints on fabricating intricate, free-standing structures. Moreover, it remains a significant challenge to design and spatially control liquid crystal orientation within complex 3D structures to achieve desired shape transformations. To address these challenges, this study introduces a 4D printing strategy that combines two-stage UV-curable LCEs with vat photopolymerization-based 3D printing, such as digital light processing (DLP). The LCE can be initially printed into complex geometries with high precision, followed by a post-printing programming step in which mechanical deformation is applied to the printed structure to define the desired shape. A subsequent thermal treatment forms covalent linkages to lock the programmed configuration. The resulting structures can reversibly transition between the printed and programmed configurations upon temperature change. This 4D printing strategy is shown to overcome key limitations of current approaches and significantly broaden the design space and functional potential of programmable shape-changing structures for various applications, including mechanically active metamaterials, morphing architecture, and soft robotics. 
    more » « less
  3. ; ; ; ; (, Crystals)
    null (Ed.)
    Stimuli-responsive materials that exhibit a mechanical response to specific biological conditions are of considerable interest for responsive, implantable medical devices. Herein, we report the synthesis, processing and characterization of oxidation-responsive liquid crystal elastomers that demonstrate programmable shape changes in response to reactive oxygen species. Direct ink writing (DIW) is used to fabricate Liquid Crystal Elastomers (LCEs) with programmed molecular orientation and anisotropic mechanical properties. LCE structures were immersed in different media (oxidative, basic and saline) at body temperature to measure in vitro degradation. Oxidation-sensitive hydrophobic thioether linkages transition to hydrophilic sulfoxide and sulfone groups. The introduction of these polar moieties brings about anisotropic swelling of the polymer network in an aqueous environment, inducing complex shape changes. 3D-printed uniaxial strips exhibit 8% contraction along the nematic director and 16% orthogonal expansion in oxidative media, while printed LCEs azimuthally deform into cones 19 times their original thickness. Ultimately, these LCEs degrade completely. In contrast, LCEs subjected to basic and saline solutions showed no apparent response. These oxidation-responsive LCEs with programmable shape changes may enable a wide range of applications in target specific drug delivery systems and other diagnostic and therapeutic tools. 
    more » « less
  4. ; (, Advanced Functional Materials)
    Abstract Stimuli‐responsive soft materials (SRSMs) can change shape in response to external stimuli, such as heat or light, through non‐equilibrium kinetic processes like diffusion and viscoelastic relaxation. Steering the non‐equilibrium kinetic processes is crucial to enable programmable spatiotemporal shape morphing of SRSMs. However, achieving such behavior through simple control and facile fabrication remains a challenge. Herein, by regulating the non‐equilibrium kinetic processes in photothermally responsive shape memory polymer (SMP) strips, their programmable spatiotemporal shape‐morphing is demonstrated with a simple material system and constant external stimuli. Specifically, it is shown that how varying the angles of light incidence, light intensity, and material properties encode the programmable spatiotemporal behaviors. These experiments manifest that an SMP strip displays convexity inversion, flip‐forward motion, and rolling behavior in response to constant light illumination. Furthermore, it is shown that a twisted SMP strip exhibits different untwisted directions under different concentrated illumination areas. Finally, materials are patterned with different kinetic properties in an SMP strip, demonstrating the capability of SMPs to undergo more complex spatiotemporal shape‐morphing behaviors, such as twisted bending. This work achieves programmable spatiotemporal shape‐morphing behaviors of SMP by utilizing material intelligence, and provides essential design guidelines for morphing structures and soft robots. 
    more » « less
  5. ; ; ; ; ; ; ; ; ; (, Advanced Functional Materials)
    Abstract 4D printing is the 3D printing of objects that change chemically or physically in response to an external stimulus over time. Photothermally responsive shape memory materials are attractive for their ability to undergo remote activation. While photothermal methods using gold nanorods (AuNRs) are used for shape recovery, 3D patterning of these materials into objects with complex geometries using degradable materials is not addressed. Here, the fabrication of 3D printed shape memory bioplastics with photo‐activated shape recovery is reported. Protein‐based nanocomposites based on bovine serum albumin (BSA), poly (ethylene glycol) diacrylate (PEGDA), and AuNRs are developed for vat photopolymerization. These 3D printed bioplastics are mechanically deformed under high loads, and the proteins served as mechano‐active elements that unfolded in an energy‐dissipating mechanism that prevented fracture of the thermoset. The bioplastic object maintained its metastable shape‐programmed state under ambient conditions. Subsequently, up to 99% shape recovery is achieved within 1 min of irradiation with near‐infrared (NIR) light. Mechanical characterization and small angle X‐ray scattering (SAXS) analysis suggest that the proteins mechanically unfold during the shape programming step and may refold during shape recovery. These composites are promising materials for the fabrication of biodegradable shape‐morphing devices for robotics and medicine. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Text Encoded Conversion
  • XML
  • Save / Share this Record
  • Send to Email