About

Zhigang Suo is the Allen E. and Marilyn M. Puckett Professor of Mechanics and Materials at Harvard John A. Paulson School of Engineering and Applied Sciences. He is also a Kavli Scholar at the Kavli Institute for Bionano Science & Technology. His primary teaching areas include Materials Science and Mechanical Engineering. His research focuses on applied mathematics, modeling physical and biological phenomena and systems, applied physics, and materials science, with particular emphasis on soft matter, solid mechanics, and materials engineering. Recognized for his scientific achievements, Suo was elected to the American Academy of Arts & Sciences. His work has contributed to developing tougher, longer-lasting, and more sustainable materials, including innovations in natural rubber reinforcement and crack-resistant rubber.

Research topics

• Composite material
• Materials science
• Nanotechnology
• Polymer chemistry
• Polymer science
• Computer Science
• Electrical engineering
• Chemistry
• Engineering
• Optoelectronics
• Physics
• Chemical physics
• Condensed matter physics
• Organic chemistry
• Chemical engineering
• Physical chemistry

Selected publications

• Amplifying toughness in silica-reinforced natural rubber by preserving long chains

  Proceedings of the National Academy of Sciences · 2026-03-23 · 1 citations

  articleOpen accessSenior authorCorresponding

  Natural rubber outperforms synthetic rubbers because of its long chains and strain-induced crystallization (SIC). However, these advantages are largely lost when the natural rubber chains are masticated during processing, and silica particles are added for reinforcement. Mastication eases mixing but shortens chains and lowers performance. Silica particles require covalent interlinks with rubber chains, but these interlinks restrict chain stretch and alignment, reducing SIC. Here, we show that the performance of silica-reinforced natural rubber can be markedly enhanced by preserving long natural rubber chains. We use a solvent to dissolve natural rubber latex into individual rubber chains and use the solution to uniformly disperse silica particles. After drying, the uncured compound can be stored and molded prior to curing. The long rubber chains are then sparsely crosslinked with one another and interlinked with the silica particles. The long strands readily align under stretch and increase SIC. Preserving long chains elevates toughness by an order of magnitude, from ~2 to 44 kJ m –2 . High toughness arises from energy dissipation across multiple length scales, over long rubber strands, silica particles, and a zone of SIC. High modulus of ~19 MPa arises from two interpenetrating networks: the network of densely entangled rubber chains and the network of percolated silica particles. The resulting material achieves high toughness while maintaining high modulus, a combination uncommon in silica-reinforced synthetic and natural rubbers.

  PublisherDOI

• Polymers Resist Fatigue Crack Growth by Deconcentrating Stress

  Annual Review of Materials Research · 2025-04-01 · 12 citations

  articleOpen accessSenior author

  When a material is cyclically loaded, an amplitude of load exists, called the threshold, below which a crack does not grow. In a polymeric material, physical interactions between polymer chains are much weaker than covalent bonds between repeat units along an individual chain. Consequently, when a crack impinges on a chain, high tension transmits along a long length of the chain. Breaking a single covalent bond dissipates the energy stored in that long length. The longer the length over which high tension transmits, the higher the threshold. Here we review how stress deconcentrates in diverse polymeric materials, including polymer networks, particle-reinforced elastomers, glassy polymers, semicrystalline polymers, phase-separated polymers, and composites. Ample opportunities exist for investigation and innovation.

  PublisherDOI

• Unusually long polymers crosslinked by domains of physical bonds

  Nature Communications · 2025-05-22 · 37 citations

  articleOpen accessSenior author

  Polymers crosslinked by covalent bonds suffer from a conflict: dense covalent crosslinks increase modulus but decrease fatigue threshold. Polymers crosslinked by physical bonds commonly have large hysteresis. Here we simultaneously achieve high modulus, high fatigue threshold, and low hysteresis in a network of unusually long polymer chains crosslinked by domains of physical bonds. When the network without precrack is pulled by a moderate stress, chains in the domains slip negligibly, so that the domains function like hard particles, leading to high modulus and low hysteresis. When the network with a precrack is stretched, the chains in the domains at the crack tip slip but do not pull out. This enables high tension to transmit over long segments of chains, leading to a high fatigue threshold. Crosslinked polymers often suffer from increased modulus with decreased fatigue threshold or large hysteresis. Here the authors achieve high modulus, high fatigue threshold, and low hysteresis in a network of unusually long polymer chains crosslinked by domains of physical bonds.

  PublisherOA PDFDOI

• Why is the strength of a polymer network so low?

  ArXiv.org · 2025-02-17 · 2 citations

  preprintOpen access

  Experiments have long shown that a polymer network of covalent bonds commonly ruptures at a stress that is orders of magnitude lower than the strength of the covalent bonds. Here we investigate this large reduction in strength by coarse-grained molecular dynamics simulations. We show that the network ruptures by sequentially breaking a small fraction of bonds, and that each broken bond lies on the minimum "shortest path". The shortest path is the path of the fewest bonds that connect two monomers at the opposite ends of the network. As the network is stretched, the minimum shortest path straightens and bears high tension set by covalent bonds, while most strands off the path deform by entropic elasticity. After a bond on the minimum shortest path breaks, the process repeats for the next minimum shortest path. As the network is stretched and bonds are broken, the scatter in lengths of the shortest paths first narrows, causing stress to rise, and then broadens, causing stress to decline. This sequential breaking of a small fraction of bonds causes the network to rupture at a stress that is orders of magnitude below the strength of the covalent bonds.

  PublisherOA PDFDOI

• Secreting salt glands constrain cuticle fracture to enhance desalination efficiency

  bioRxiv (Cold Spring Harbor Laboratory) · 2025-02-28

  preprintOpen access

  ABSTRACT Plants responding to excessive soil salinity by discharging brine onto their leaf surface risk dehydration through the osmotic continuity between the living tissue and the surface brine, which further enriches with evaporation. Cuticle cracks have long been identified as essential for salt to reach the leaf surface but provide the potentially desiccating continuity between the brine and the gland interior. Using the secreting salt gland of Nolana mollis as a model system, we integrate mathematical modeling, imaging, and physiological measurements to examine the mechanical and biochemical processes required for efficient desalination. We find that the subcuticular space between the concentrated surface brine and the more dilute secreting cell eases the energetic limits of active desalination by reducing the concentration gradient of salt across the cell membrane. We show that crack size plays a critical role in balancing the osmotic and pressure gradients required for salt removal without runaway foliar desiccation.

  PublisherOA PDFDOI

• Viscoelasticity and crack growth in tanglemers

  Extreme Mechanics Letters · 2025-11-13

  articleSenior authorCorresponding
  PublisherDOI

• Natural rubber with high resistance to crack growth

  Nature Sustainability · 2025-05-07 · 31 citations

  articleSenior author
  PublisherDOI

• Thermodynamic and Molecular Origins of Crack Resistance in Polymer Networks

  Chemical Reviews · 2025-12-15 · 8 citations

  reviewSenior authorCorresponding

  A material tears, peels, and breaks by growing a crack. In a zone around the crack front, atoms undergo an irreversible process of breaking─and possibly reforming─bonds. Trailing behind the crack front are two layers of scars. Outside the irreversible zone and scars, atoms undergo the reversible process of elasticity. The irreversible zone is considered localized if it is small relative to the body. The idealization of localized irreversibility leads to a thermodynamic framework centered on the energy release rate. This crack driving force is defined using an ideal body in which a crack is stationary and deformation is elastic, and is applied to a real body in which a crack grows by an irreversible process. The irreversible zone scales with a material length: the fractocohesive length. We review recent advances in the development of crack-resistant elastomers and hydrogels as well as polymer networks reinforced by hard particles, fibers, or fabrics, subject to monotonic, cyclic, and static loading. Emphasis is placed on how molecular features, such as strand length, entanglements, noncovalent bonds, and chemical reactions, govern crack resistance. Design principles are highlighted that reconcile high toughness with low hysteresis through stress deconcentration. This review traces crack resistance to molecular origins, providing a foundation for designing next-generation crack-resistant materials.

  PublisherDOI

• Cyclic tearing of a woven fabric embedded in a soft matrix

  International Journal of Fracture · 2025-01-08 · 2 citations

  article
  PublisherDOI

• How does chain length affect fracture of a brittle polymer glass?

  SSRN Electronic Journal · 2025-01-01

  preprintOpen accessSenior author
  PublisherDOI

Recent grants

• Large Deformation and Instability in Soft Active Materials

  NSF · $302k · 2008–2011

Frequent coauthors

• Joost J. Vlassak

  50 shared

• S. Wagner

  Princeton University

  39 shared

• Qihan Liu

  36 shared

• Xuanhe Zhao

  Massachusetts Institute of Technology

  36 shared

• Tongqing Lu

  31 shared

• Choon Chiang Foo

  Agency for Science, Technology and Research

  29 shared

• Guogao Zhang

  Peking University Shenzhen Hospital

  28 shared

• Christoph Keplinger

  University of Colorado Boulder

  28 shared

Awards & honors

• Elected to American Academy of Arts & Sciences (2024)