About

Shengqiang Cai is a Professor in the Program in Materials Science and Engineering at the University of California, San Diego. His research focuses on the mechanics of soft materials, including hydrogels and elastomers, and their response to stimuli, which enables their functions. He has formulated theories to better understand the interplay of mechanics with chemistry, electricity, and temperature in soft materials. Cai's work also involves studying ways to use soft active materials to convert energy in various forms. Currently, he is investigating how to design and optimize structures made of soft materials to provide functions such as energy harvesting, fluid regulation, and desalination of salt water. Additionally, he explores the mechanical instability phenomena associated with large deformation in soft materials to guide electromagnetic waves and other functionalities. Cai's background includes a Ph.D. in mechanical engineering from Harvard University earned in 2011, a master's of engineering, and a bachelor's of science from the University of Science and Technology of China. He was a postdoctoral fellow at the Massachusetts Institute of Technology from 2011 to 2012. His research aims to advance the understanding and application of soft materials through innovative theories and design strategies.

Research topics

• Computer Science
• Materials science
• Engineering
• Optoelectronics
• Nanotechnology
• Composite material
• Electrical engineering
• Embedded system
• Cardiology
• Physics
• Biomedical engineering
• Mechanics
• Mechanical engineering
• Radiology
• Medicine

Selected publications

• High‐Performance Dielectric Liquid Crystal Elastomer Actuator Enabled by Its Unique Strain Softening

  Advanced Materials Technologies · 2026-01-15 · 2 citations

  articleOpen accessSenior authorCorresponding

  ABSTRACT Dielectric elastomer actuators (DEAs) combine light weight, large work output, fast response, and energy efficiency, making them attractive for emerging applications in soft robotics, wearable devices, and biomedical systems. However, their performance under mechanical loading is constrained by low blocking stress (<0.4 MPa). To overcome this limitation, we introduce dielectric liquid crystal elastomer actuators (DLCEA) that leverage the strain‐softening and anisotropic properties of monodomain liquid crystal elastomers (LCE). By tuning the crosslinking chemistry and mechanical alignment of the LCE network, we engineer DLCEAs capable of delivering large actuation strains (>20%) and significantly enhanced work output under large loads (>1.5 MPa). The optimized DLCEA achieves specific energy densities reaching 440 J/kg at low frequencies (0.5 Hz) and peak power densities of 9100 W/kg at resonance (10 Hz), outperforming state‐of‐the‐art DEAs. Demonstrations include high‐load actuation and fluid pumping with a single‐layer actuator, highlighting the potential of DLCEAs for scalable, high‐performance electromechanical systems.

  PublisherOA PDFDOI

• Liquid Crystal Elastomer Foam–Based Pressure-Sensitive Adhesives with Enhanced Adhesion

  SSRN Electronic Journal · 2026-01-01

  preprintOpen accessSenior author
  PublisherDOI

• Enhanced Poynting effect in torsion of a polydomain liquid crystal elastomer cylinder

  Journal of the Mechanics and Physics of Solids · 2026-04-02

  articleSenior author
  PublisherDOI

• Bio‐Inspired Artificial Muscle‐Tendon Complex of Liquid Crystal Elastomer for Bidirectional Afferent‐Efferent Signaling (Adv. Mater. 2/2026)

  Advanced Materials · 2026-01-01 · 1 citations

  articleOpen access

  Bio-Inspired Artificial Muscles In their Research Article (DOI: 10.1002/adma.202503094), Shengqiang Cai, Yong-Lae Park, and co-workers report a bio-inspired artificial muscle–tendon complex (MTC) based on liquid crystal elastomers (LCEs) with embedded liquid-metal channels, illustrated as an artificial actuator connected to biological muscle in the image. The MTC integrates both actuation and proprioceptive sensing within a single structure, enabling simultaneous efferent actuation and afferent feedback. Mimicking natural musculature through an antagonistic arrangement, the system achieves closed-loop bidirectional control, demonstrated in robotic finger and gripper applications.

  PublisherOA PDFDOI

• Advancing Renewable Materials via Microalgae-Derived Thermoplastic Polyester Polyurethanes

  ACS Sustainable Chemistry & Engineering · 2025-12-05 · 2 citations

  article

  To remediate the growing global impacts of plastic waste, it is imperative to design sustainable materials that can be used as replacements for current nonrenewable and nonbiodegradable commercial products. Addressing this issue requires careful selection of both material class and renewable feedstock source to maximize the sustainability of production processes and end-of-life outcomes. This work describes the use of microalgae as a renewable feedstock for preparation of thermoplastic polyester polyurethane (TPU) materials. The sustainable and robust photosynthetic capacity of microalgae paired with cleavable bonds within the polyester TPU backbone result in a material that promotes efficient resource use and reduced ecological impact at the end of its life cycle. High-purity TPU monomers derived from Nannochloropsis salina oil were used to synthesize the first 100% microalgae-sourced TPU material from azelaic acid (AzA), 1,7-heptamethylene diisocyanate (7-HDI), and 1,9-nonanediol (NDO). For comparison, a TPU containing 75% microalgae-content was also prepared utilizing industry-standard 1,3-propanediol (PDO). Thermal and mechanical characterization was used to analyze the structure–function properties of the TPUs and assess potential industrial applications. Overall, this work seeks to offer a viable alternative to conventional plastics, supporting the global transition toward sustainable plastic usage.

  PublisherDOI

• High-efficiency carbon dioxide capture using macroporous hydrogel infused with microalgal amino acid salt solution

  Fuel · 2025-09-01

  article
  PublisherDOI

• High-flux and stable thin-film evaporation from fiber membranes with interconnected pores

  Joule · 2025-06-13 · 10 citations

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  PublisherDOI

• Fracture in hexagonal honeycomb lattices undergoing large deformation

  Extreme Mechanics Letters · 2025-11-23

  articleSenior authorCorresponding
  PublisherDOI

• Numerical study on crack tip fields in liquid crystal elastomers

  International Journal of Solids and Structures · 2025-04-12 · 2 citations

  articleOpen accessSenior authorCorresponding

  This study presents a numerical investigation into the crack tip fields in liquid crystal elastomers (LCEs) using finite element simulations. LCEs exhibit unique mechanical behaviors, such as soft elasticity and directionally adjustable anisotropy, due to the coupling between the deformation of polymer networks and the rotation of liquid crystal mesogens. The numerical simulations focus on a rectangular LCE plate with a small central crack, subjected to uniform stretching. Simulation results reveal the presence of a uniaxial stress state near the crack tip and a universal stress singularity obeying a power law with an exponent of −1. Along the circumferential direction around the crack tip, the stress distribution exhibits a prominent polarization, with the polarization direction precisely aligned with the initial mesogen orientation. For the mesogen reorientation at the crack tip, two types of mesogen rotation—rigid body rotation with the polymer network and relative rotation due to network stretching—are distinguished. The rigid body rotation is found to cause significant heterogeneity in mesogen orientation at the crack tip, but the relative rotation tends to make the mesogen orientation more uniform, generally aligning with the direction of applied stretch. The final mesogen orientation, determined by the initial orientation and rotation, is closely related to the magnitude of the stress field at the crack tip. These findings provide valuable insights into the fracture behavior of LCEs and can serve as a foundation for future experimental and theoretical studies.

  PublisherDOI

• Finite Element Model of the Effect of Optic Nerve Sheath Anisotropy on Ocular Loading During Horizontal Duction

  Bioengineering · 2025-05-29 · 3 citations

  articleOpen access

  Previous models of extraocular mechanics have often assumed isotropic properties for ocular tissues, despite evidence indicating anisotropy in the optic nerve sheath (ONS). To investigate this further, we developed a finite element model (FEM) of horizontal eye rotation using MRI data from a living subject with normal tension glaucoma. Mechanical properties were derived from tensile tests on 17 post-mortem human eyes, revealing previously unrecognized anisotropic characteristics in the ONS. We simulated ±32° horizontal eye rotations and compared isotropic versus anisotropic ONS properties using the Holzapfel model. Strain distributions in the optic nerve (ON) were analyzed using ABAQUS 2024 software. During 32° adduction, stress and strain were concentrated at the ONS-sclera junction, reaching 8 MPa and 40% with isotropic properties, and 15 MPa and 30% with anisotropic properties. In contrast, during 32° abduction, stress was lower and strain was higher in the isotropic case (6 MPa and 30%) compared to the anisotropic case (12 MPa and 25%). Increased intraocular and intracranial pressures had minimal impact on the mechanical responses. These findings suggest that the anisotropic properties of the ONS increase stress concentration at the optic disc while reducing strain during eye movements, offering new insights into ocular biomechanics. A novel phenomenon emerged from the simulations: during larger ductions, the peripapillary Bruch's membrane is predicted to wrinkle, forming undulations with an approximately 20 μm amplitude and 100 μm wavelength at its interface with the retina and choroid.

  PublisherOA PDFDOI

Recent grants

• Collaborative Research: Dynamics of Surface Instability Propagation in Soft Materials

  NSF · $163k · 2015–2018

• CAREER: Experimental and Theoretical Studies of Mechanics Interacting with Electric/Optical Fields in Liquid Crystal Elastomers

  NSF · $592k · 2016–2022

• Design and Investigation of Electrospun Artificial Muscle Fibers

  NSF · $438k · 2018–2022

• Chemo-Mechanical Coupling in the Erosion of Degradable Polymers

  NSF · $331k · 2021–2024

Frequent coauthors

• Zhijian Wang

  Shenyang Aerospace University

  32 shared

• Qiguang He

  Tianjin University of Technology and Education

  31 shared

• Zhigang Suo

  Harvard University

  27 shared

• Kai Li

  26 shared

• Zhaoqiang Song

  Northwestern Polytechnical University

  22 shared

• Yang Wang

  21 shared

• Chenghai Li

  University of California, San Diego

  19 shared

• Yue Zheng

  Drexel University

  19 shared