Liquid crystal elastomer shell actuators with negative order parameter.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 30993207.
- Also identified by DOI 10.1126/sciadv.aaw2476 and PMC identifier 6461453.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Liquid crystals (LCs) are nonsolids with long-range orientational order, described by a scalar order parameter <math xmlns="http://www.w3.org/1998/Math/MathML"> <mrow><mrow><mo>〈</mo> <msub><mi>P</mi> <mn>2</mn></msub> <mo>〉</mo> <mo>=</mo> <mfrac><mn>1</mn> <mn>2</mn></mfrac> <mo>〈</mo> <mn>3</mn> <msup><mtext>cos</mtext> <mn>2</mn></msup> <mi>β</mi> <mo>-</mo> <mn>1</mn> <mo>〉</mo></mrow> </mrow> </math> . Despite the vast set of existing LC materials, one-third of the order parameter value range, <sup>-1</sup>/<sub>2</sub> < 〈<i>P</i> <sub>2</sub>〉 < 0, has until now been inaccessible. Here, we present the first material with negative LC order parameter in its ground state, in the form of elastomeric shells. The optical and actuation characteristics are opposite to those of conventional LC elastomers (LCEs). This novel class of anti-ordered elastomers gives access to the previously secluded range of liquid crystallinity with 〈<i>P</i> <sub>2</sub>〉 < 0, providing new challenges for soft matter physics and adding a complementary type of LCE actuator that is attractive for applications in, e.g., soft robotics.