Bio

B.S. Physics, Lanzhou University, 2006Ph.D. Materials Science, University of North Carolina at Chapel Hill, 2012Postdoctoral Fellow, Harvard University, 2013-2017

"We aim to understand and control the interactions between adaptive soft materials and living systems to solve challenges in sustainability and health."

Liheng Cai, ASSISTANT PROFESSOR

My lab’s research lies at the interface of soft (bio)materials and biology. We seek to understand and control the interactions between soft (bio)materials and living systems to solve challenges in sustainability and health. We do this using a combination of experimental and theoretical approaches. Our core expertise is polymers and soft matter, biomaterials, voxelated bioprinting, and additive manufacturing of soft/inorganic matter, complemented by cell biology, nonlinear fluid dynamics, macro-/micro-rheology, advanced characterization, microscopy and image analysis, and microfluidics. Recently, we successfully expanded our capability to in vivo animal studies. Our research is highly collaborative and interdisciplinary. The philosophy of our research is to identify and solve problems of both fundamental importance and practical value; this is often accomplished by working closely with experts from various fields. Members of our group often start with one area of research and gradually broaden their horizon spanning from physics, chemistry, biology, engineering to medicine. 

We focus on three directions:

  • 3D printing of adaptive soft materials. Existing polymers for 3D printing are largely limited to stiff plastics. We develop new design principles to create 3D printable soft materials. Integrating polymer chemistry, polymer physics, molecular theory, and multi-scale modeling, we are establishing molecule-structure-property-function relations for new classes of adaptive soft materials. By developing various kinds of 3D printing techniques, we transform these materials to multi-material, functional organic/inorganic architectures for applications including soft robots, tissue engineering, and catalysis. 

  • Programmable cell assembly. Inspired by Minecraft, a popular video game that uses individual 3D cubes as voxels to create a virtual world, we develop voxelated bioprinting technologies to assemble cell encapsulated droplets to create 3D cell assemblies with programmed architecture and function. Research along this direction includes: (1) development of voxelated bioprinting platform, (2) design and synthesis of modular biomaterials, and (3) engineering functional tissue mimics. 

  • Human lung defense. As we are alive, we must breathe. This process of breathing brings bacterial, viral, and environmental particulates into our lungs. How can the lungs fight against them? To answer this question, we develop micro-human airway device to capture the geometric and biological features of human airway and exploit this device to study human lung defense. Integrating soft matter physics, engineering, molecular biology, bioinformatics, and systems biology, we are investigating the interactions between mucus and three indispensable components of the microenvironment: cilia, cells, and bacteria.

Awards

  • UVA Research Excellence Award 2023
  • ACS PRF Doctoral New Investigator Award 2020
  • NSF CAREER Award 2019
  • Harvard University Postdoctoral Award for Professional Development 2014
  • North Carolina Impact Award 2013
  • Chun-Tsung Scholar 2004

Research Interests

  • Soft (bio)Materials
  • Polymers
  • Biophysics
  • Biofilms
  • Additive Manufacturing

In the News

  • STRETCHING POSSIBILITIES: RESEARCHER IMAGINES SUPER RUBBER, AND HAS A STRATEGY TO MAKE IT


    What’s 1,000 times softer than a rubber tire, but holds its shape and is as tough as metal?

    The answer is nothing – yet. But a soft material with that combination of properties would be extremely useful in many applications, including medical implants, stretchable electronics or lifelike “soft robots” capable of adapting to unpredictable conditions – as humans and animals do – in ways traditional robots cannot.

    University of Virginia School of Engineering assistant professor Liheng Cai believes his lab has found a way to design a new synthetic rubber with these traits. Cai holds joint appointments in UVA Engineering’s departments of Materials Science and Engineering and Chemical Engineering, with a courtesy appointment in the Department of Biomedical Engineering.

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  • CAREER Award: Running Hot and Cold


    Liheng Cai Earns Prestigious National Science Foundation Award to Develop Polymeric Material to Control the Types of Energy Streaming into Windows with the Flick of a Switch

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  • Eliminating entanglements

    A new strategy towards ultra-soft yet dry rubber


    Medical implants mimic the softness of human tissue by mixing liquids such oil with long silicone polymers to create a squishy, wet gel. While implants have improved dramatically over the years, there is still a chance of the liquid leaking, which can be painful and sometimes dangerous.

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  • Tough, self-healing rubber

    Potential applications include more durable tires, wearable electronics, medical devices


    Imagine a tire that could heal after being punctured or a rubber band that never snapped.

    Researchers from the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) have developed a new type of rubber that is as tough as natural rubber but can also self-heal.

    The research is published in Advanced Materials.

    Self-healing materials aren’t new — researchers at SEAS have developed self-healing hydrogels, which rely on water to incorporate reversible bonds that can promote healing. However, engineering self-healing properties in dry materials — such as rubber — has proven more challenging. That is because rubber is made of polymers often connected by permanent, covalent bonds. While these bonds are incredibly strong, they will never reconnect once broken.

    In order to make a rubber self-healable, the team needed to make the bonds connecting the polymers reversible, so that the bonds could break and reform.

    “Previous research used reversible hydrogen bonds to connect polymers to form a rubber but reversible bonds are intrinsically weaker than covalent bonds,” said Li-Heng Cai, a postdoctoral fellow at SEAS and corresponding author of the paper.  “This raised the question, can we make something tough but can still self-heal?”

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  • 'Brush' offers clues to fighting lung disease


    Scientists say the discovery of an internal "brush" that helps clear lungs of unwanted matter could help them understand more about lung diseases.

    A team from the University of North Carolina found that the brush-like layer pushes out sticky mucus and the foreign bodies it contains.

    Writing in Science, it says that could help identify what goes wrong in cystic fibrosis, asthma and similar diseases.

    UK lung experts said the work aided understanding of how lungs function.

    The mucus, which helps collect inhaled pollutants, emerges as a runny nose and a wet cough.

    Until now, most experts believed a watery substance acted as a lubricant and helped separate mucus from the cells lining airways.

    But this did not tally with the fact that mucus remained in its own distinct layer.

    The researchers used imaging techniques to examine what was happening within the lungs.

    They were able to see a dense meshwork of human bronchial epithelial cell cultures.

    The brush-like layer consists of protective molecules that keep sticky mucus from reaching the cilia and epithelial cells, thus ensuring the normal flow of mucus.

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  • University of Virginia Engineering Researchers Strive to Match Artistry of Biological Tissues

    Team’s Work Advances Soft Matter Science for Bioprinting Materials


    In the video game Minecraft, everything including animals and characters is made of small 3D blocks called voxels. Materials scientists at the University of Virginia School of Engineering and Applied Science have developed a Minecraft-like, voxelated approach that uses droplets as the basic building blocks to create complicated structures comparable to human tissues and organs.

    Liheng Cai, an assistant professor of materials science and engineering, chemical engineering and biomedical engineering, leads the team. Jinchang Zhu, a Ph.D. student in Cai’s SOFT BIOMATTER LABORATORY, develops their bioprinting technique, digital assembly of spherical bio-ink particles or DASP.

    “In principle, DASP allows us to precisely define the location, composition and properties of individual droplets and assemble them into 3D constructs that match the artistry of biological tissues,” Zhu said.

    Using a customized 3D printer, the team extrudes and deposits bio-ink droplets inside a supporting matrix, a slurry bath that supports and holds the droplets in 3D space. The droplets swell up, come into contact with their neighboring droplets, and then solidify to form a 3D lattice structure. With combinations of droplets made of various materials or encapsulated with various components, DASP shows a large number of possibilities for designing and creating functional tissue constructs.

    Zhu first-authored the team’s original paper published October 2021 in ADVANCED FUNCTIONAL MATERIALS, where Cai and his collaborators proved the concept of voxelated bioprinting.

    “The paper we published last year was a first step toward 3D printing tissue with the complexity and organization needed for biomedical engineering, drug screening and disease modeling,” Cai said.

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  • UVA-Led Discovery Challenges 30-Year-Old Dogma in Associative Polymers Research


    A University of Virginia-led study about a class of materials called associative polymers appears to challenge a long-held understanding of how the materials, which have unique self-healing and flow properties, function at the molecular level.

    LIHENG CAI, an assistant professor of materials science and engineering and chemical engineering at UVA, who led the study, said the new discovery has important implications for the countless ways these materials are used every day, from engineering recyclable plastics to human tissue engineering to controlling the consistency of paint so it doesn’t drip.

    The discovery, which has been published in the journal Physical Review Letters, was enabled by new associative polymers developed in Cai’s lab at the UVA School of Engineering and Applied Science by his postdoctoral researcher Shifeng Nian and Ph.D. student Myoeum Kim. The breakthrough evolved from a THEORY Cai had co-developed before arriving at UVA in 2018.

    “Shifeng and Myoeum essentially created a novel experimental platform to study the dynamics of associative polymers in ways that weren’t possible before,” Cai said.

    “This gave us a new perspective on the polymers’ behavior and provides opportunities to improve our understanding of particularly challenging areas of study in polymer science. And from a technology standpoint, the research contributes to the development of self-healing materials with tailored properties.”

    Polymers are macromolecules composed of repeating units, or monomers. By rearranging or combining these units and tinkering with their bonds, scientists can design polymeric materials with specific characteristics.

    Polymers also can change states, from hard and rigid, like glass, to rubbery or even fluid depending on factors such as temperature or force — for example, pushing a solid gel through a hypodermic needle.

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  • UVA Researchers Advance Bioprinting

    New Technique Uses Hydrogel Particles to Build 3D Structures


    Minecraft is one of the world’s best-selling video games, with 126 million active players across the globe.

    In the 3D-mosaic world of Minecraft, everything – animals, houses, even the sun and the moon – is made of small cubes or voxels, the basic building blocks for 3D structures. Players customize the voxels with various functions and colors to construct their own art works. The only limitation is the players’ imagination.

    An interdisciplinary team of researchers in the University of Virginia’s School of Engineering and Applied Science and School of Medicine adopted Minecraft’s voxelated approach to advance the field of 3D bioprinting, where the goal is to engineer 3D structures that mimic the geometry, texture, and function of human tissues and organs. LIHENG CAI, an assistant professor of materials science and engineering, chemical engineering and biomedical engineering, leads the team.

    Their paper, DIGITAL ASSEMBLY OF SPHERICAL VISCOELASTIC BIO-INK PARTICLES, termed DASP, is featured as a cover article in Advanced Functional Materials. The team has earned funding from the National Science Foundation Division of Materials Research-Polymers, the American Chemical Society Petroleum Research Fund, UVA LaunchPad for Diabetes, the Virginia Commonwealth Health Research Board and the UVA Center for Advanced Biomanufacturing to support their research. 

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