Professor & Department Head
Research
Bioinspired Adhesion & Friction
Nature has beautiful examples of organisms that use adhesion for locomotion. We are developing fundamental knowledge of how these systems work in Nature, as well as guiding principles for developing synthetic materials that reproduce many of their attractive properties.
We have developed a robust scaling relationship that clearly identifies the key, governing parameters for the maximum force capacity of a reversible adhesive. This scaling relationship has led to new insight into the enabling mechanisms behind natural and synthetic bio-inspired adhesives as well as to the development of a new adhesive technology we call GeckskinTM.
We work with Prof. Duncan Irschick in the Department of Biology at UMass to understand the important lessons that has allowed Nature to scale adhesion across several orders of size, from beetles to geckos---so that we can produce materials with these properties on size scales that society can use!
Growth & Assembly
Materials that possess structural hierarchy have a special range of properties that span across several length scales from the nano- to the macroscale. A variety of examples are seen in Nature, such as collagen assembling into fibrils, fibers, and extracellular matrices and tissues. Our goal focuses on developing novel processing methods for fabricating macroscopic hierarchical structures from chemically tailored nanoscale particles and understanding their associated properties.
In collaboration with Prof. Todd Emrick, we exploit functional ligand chemistries to enable the creation of nanoparticle ribbons and fabrics that have excellent structural integrity. The nanoparticle assemblies are released from their underlying substrate to reveal flexible and robust macroscale structures. The flexibility is defined by the balance of the particle core size, ligand properties, particle packing, as well as ribbon and fabric geometry. These materials offer tremendous potential for the design of flexible electronics, new optical devices, membranes, as well as protective coatings and materials for encapsulation and delivery of small objects.
Mechanics of Gels, Tissues and Thin Films
Gels are solids that are composed of a dilute network of material within a liquid domain. Examples range from familiar items like Jell-O to biomaterials, like the the lens of an eye, to hydrogels, like those found in absorbant diapers. The mechanical behavior of these materials is key to their utilization in both nature and new technology and is a function of the microstructural make-up of the material. Currently, our group characterizes this microstructure/property relationship from both design and property measurement perspectives. To this end, we have developed a novel characterization technique we call Cavitation Rheology that is capable of locally quantifing the mechanical properties of soft materials, such as hydrogels.
Cavitation Rheology
Cavitation Rheology takes advantage of the unique elastic instability associated with non-linear elastic materials. This instability is the result of favorable growth for a bubble, or cavity, at some critical pressure related to the local elastic modulus combined with the energetic cost associated with the surface energy of the growing bubble. We are utilizing this technique to probe the mechanical properties of varieties of synthetic materials as well as living tissues. An example of the latter is shown in the image on the right in which cavitation measurements are being performed in order to correlate disease in mouse skin with mechanical response. Simultaneously, we characterize the fundamental principles governing a cavitation event under changes in local geometry (e.g.., confinement of the material being tested) and loading conditions (e.g., loading rate) in synthetic hydrogels and soft polymers.
Autonomous and Controlled Movement with Soft Materials
Upon the development of a critical stress, many materials and geometries experience a mechanical instability, which produces significant changes in geometry with small changes in stress. In nature, mechanical instabilities are ubiquitous with well-defined shapes, morphologies, and functions. For instance, in the emergence of mountains and valleys and at a smaller scale such as fingerprint formation and the snapping of the Venus Flytrap. Inspired by these examples, we are interested in understanding the parameters that influence the evolution of buckled structures and take advantage of their morphologies to control the function of soft polymer surfaces.
Studying the mechanics of wrinkles and folds, as well as crumpling and snapping surfaces, provide us with fundamental insights of the nonlinear deformation of polymer films. In addition, this knowledge allows for the fabrication of unique patterned surfaces that can be controlled reversibly.
From an application point of view, controlling surface instabilities can be used to tune properties ranging from adhesion to optics. Fundamental knowledge of surface instabilities will also lead to novel technological application relevant in the development of lightweight, flexible electronics and responsive surfaces for biological applications.
Outreach
The Crosby Research Group often hosts student and community groups, of all ages (K-12, undergraduate), or participates in science education outreach events. For more information on how we may be able to work with your group's goals, please contact Prof. Crosby at @email.
News from the Crosby Research Group
More news from the Crosby GroupHierarchical Adhesion and Friction Control
Hierarchical adhesion and friction are central to how materials interact with their environment, governing functions ranging from attachment and locomotion to energy dissipation and load transfer. Our research investigates how interactions across multiple length scales, from molecular bonding to structured interfaces, influence adhesive and frictional performance.
Mechanically Transparent Adhesive Technology
StretchSeam™ is a solvent-free, UV-curable adhesive technology designed in the Crosby Research Group to bond soft, stretchable materials such as fabrics, foams, and complex materials. Unlike sewing or conventional adhesive tapes, StretchSeam™ forms soft, seamless joints that stretch and deform with the material, avoiding stress concentrations, punctures, and delamination under large deformation.
The science behind StretchSeam™ is based on a dual-network polymer architecture, inspired by the architecture in dragline spider silk, that combines strength and elasticity at the molecular level. This design allows the adhesive’s mechanical properties to be tuned to closely match those of the bonded materials, creating “mechanically transparent” seams that preserve comfort, durability, and performance. Rapid UV curing enables fast, energy-efficient processing without the use of volatile solvents, making the technology attractive for advanced manufacturing applications in footwear, apparel, medical devices, and other soft-material systems.
https://pubs.acs.org/doi/10.1021/acsami.5c03202
Impact Mitigation through Adhesive Interfaces in Metamaterials
Mechanical metamaterials provide unique opportunities to control how forces propagate through structured materials. Our work explores architected lattices that form internal adhesive interfaces during compression, creating an additional mechanism for energy storage and dissipation beyond geometry alone. By incorporating adhesive contacts within the metamaterial architecture, we demonstrate the ability to reshape stress-wave propagation, reduce transmitted impact forces, and lower overall impulse during dynamic loading. These effects scale with the number of adhesive interfaces, establishing adhesion as a new design parameter for impact-mitigating materials and protective systems.
Mechanics of Gels, Tissues, Thin Films
The mechanical behavior of soft gels and thin polymer films is an important reason for why these materials are used in both nature and advanced technologies; however, measuring their mechanical behavior in order to overcome limitations and make improvements is challenging. Our group has worked to characterize the mechanical behavior of these difficult-to-handle materials through the development of novel techniques, including Cavitation Rheology, Puncture Mechanics, and the Uniaxial Tensile Tester for Ultrathin Films (TUTTUT). Building on these foundations, our group currently investigates the mechanics of thin polymer films and how puncture mechanics can provide pathways to high-throughput mechanical characterization for engineered and natural materials.
Thin film mechanics
Our work on thin film mechanics focuses on understanding how geometric confinement alters the mechanical and fracture behavior of polymer systems. For example, we are studying how new materials that can form the backbone of a circular materials economy can be improved by reducing film thickness to influence crystallization kinetics, morphology, and load-bearing network formation. By combining thin-film processing, mechanical testing, and structural characterization, this research establishes design principles for tuning durability, toughness, and aging behavior in materials, with relevance to applications such as sustainable packaging.
Puncture Mechanics
Our work on puncture mechanics examines how puncture can serve as a characterization method integrating principles of fracture mechanics, large-deformation elasticity, and contact phenomena, making it well-suited to capture the complex failure behavior of biological tissues and bio-inspired materials. We have applied puncture mechanics theory across a broad array of biological tissues and soft solids, examining how experimental design and rate-dependent material behavior each influence the measured mechanical response. A parallel effort investigates how confining ultra-soft gels both in height and radial dimensions alters the puncture boundary conditions, and ultimately the measured elastic and fracture response. Together, these directions aim to improve cross-study comparability in biological material characterization and open new avenues for designing and characterizing next-generation soft materials.
https://academic.oup.com/icb/article/doi/10.1093/icb/icag097/8714986
Impulsive Deformations
Impulse deformation refers to the rapid, power-amplified mechanical response that arises when elastic energy stored in soft materials is suddenly released through geometric or material instabilities. Using high-speed imaging, we resolve the snapping dynamics of elastic materials and soft structures with systematically varied geometry and topology. These systems reach extreme accelerations and velocities comparable to biological exemplars such as trap jaw ants, mantis shrimp, and the Venus flytrap, while exhibiting minimal energy dissipation.
Our work is inspired by Latch-mediated Spring Actuation (LaMSA), a power-amplification strategy widely used in nature. In LaMSA systems, elastic energy is slowly loaded while motion is constrained by a latch, and then rapidly released once the latch is removed or an instability threshold is crossed. By recreating LaMSA-like behavior in synthetic materials, we study how impulse deformation emerges from the coupling between elasticity, swelling, boundary conditions, and snap-through instabilities.
A key focus of our research is autonomous, self-repeating impulse deformation in evaporation-driven polymer gels. By simultaneously measuring force accumulation during solvent evaporation and the evolving deformation profile, we establish scaling relationships that combine Flory–Rehner swelling theory with buckling mechanics. This approach enables dramatic enhancement of snapping lifetime and power output, achieving power densities comparable to biological jumpers at similar length scales.
https://www.nature.com/articles/s41563-020-00909-w
We also investigate how polymer network architecture controls solvent transport and poroelastic relaxation, directly regulating impulse behavior. Comparative studies of linear and bottlebrush elastomer networks reveal how molecular design governs permeability, swelling, and mechanical response, providing new pathways to engineer fast, efficient, and biologically inspired soft actuators.
Growth and Assembly
Growth and assembly provide powerful routes for creating complex structures from simple building blocks. Our research explores how mechanical forces, interfacial interactions, and material growth processes can be harnessed to guide shape formation across multiple length scales. By studying systems ranging from thin polymer films to fibers and mesoscale assemblies, we seek to understand how local interactions give rise to emergent structures and functional behavior.
https://doi.org/10.1002/smll.202507151
Fiber and ribbons are investigated since they are used in our daily lives, from applications in textiles to creating the electronics of the future. Usually fibers are drawn, but they also can be made by flow coating or lithographic processes, allowing control over properties like the local or gradient stiffness, which is uncommon for drawn fibers.
We aim to create materials that can that self-assemble or be gently directed into complex, mechanically-interlocked topologies, such as braids, knots, and weave, and “unlocked” upon the application of simple stimuli. Recent research efforts have led to self-spinning fiber bundle technologies, electric-field driven helical tendrils, and body-force microfiber weaving. We are also developing new methods for characterizing the mechanics of fibers assembled into complex topologies, integrating sensitive, large range force measurement with new ways to map bundle curvature using photogrammetry.
https://www.nature.com/articles/s41467-023-36355-w
https://www.science.org/doi/full/10.1126/sciadv.aed9514
Advances in the broad platform of growth and assembly requires building upon a wide foundation of expertise, and the Crosby research group is grateful for strong collaborations with Professor Todd Emrick, Professor Greg Grason, and other investigators in developing these advances.