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Electrothermally Driven Dynamic Instability in Molecularly Ordered Liquid Crystalline Polymers

Gao, Junfeng (2021) Electrothermally Driven Dynamic Instability in Molecularly Ordered Liquid Crystalline Polymers. Doctoral Dissertation, University of Pittsburgh. (Unpublished)

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Soft robots composed from compliant stimuli-responsive materials offer versatile actuation capabilities in small factors to unlock new pathways to program manipulation and motility. Integrating active and stimuli responsive materials as artificial muscles to power the drive mechanisms is particularly attractive. Here, we harness the work-dense responsiveness of molecularly ordered liquid crystalline elastomers (LCE), which can be powered using an array of stimuli, including heat and light. The work content of the LCE is directed by the patterned molecular order to interact with the geometry to drive mechanical non-linearities. Reversible actuation profiles that are impulsive in nature are demonstrated.

In this dissertation, we present a tape spring-like, transversely curved composite shell fabricated from liquid crystalline elastomer with uniaxial molecular order (monodomain), polyethylene terephthalate (PET) and an encapsulated electrode. We demonstrated ultrafast snap through instability (~ms) with ~200mW electrical power inputs at low voltages (~1V). This system is a latch mechanism. Before the occurrence of snap through motion, mechanical energy is built up in PET substrate (latched on), while remaining latent. Upon reaching the edge of the instability, the latch is spontaneously released, and an impulsive actuation is realized. The performance of these actuators against external loads is explored and approaches for modulating the latency are presented. This actuation was harnessed in sub-gram scale soft robotics, including water strider mimicking configurations and steerable robotics on a range of topographies.


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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
Gao, JunfengJUG46@pitt.eduJUG460000-0002-4564-0429
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairShankar,
Committee MemberBidanda,
Committee MemberChun,
Committee MemberTemel,
Date: 3 September 2021
Date Type: Publication
Defense Date: 6 May 2021
Approval Date: 3 September 2021
Submission Date: 1 July 2021
Access Restriction: 2 year -- Restrict access to University of Pittsburgh for a period of 2 years.
Number of Pages: 110
Institution: University of Pittsburgh
Schools and Programs: Swanson School of Engineering > Industrial Engineering
Degree: PhD - Doctor of Philosophy
Thesis Type: Doctoral Dissertation
Refereed: Yes
Uncontrolled Keywords: liquid crystalline elastomers, mechanical non-linearities, snap-through instability, latch mechanism, soft robotics
Date Deposited: 03 Sep 2021 15:32
Last Modified: 03 Sep 2023 05:15


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