Showing papers by "Jianyu Li published in 2021"

Multifaceted Design and Emerging Applications of Tissue Adhesives.

Abstract: Tissue adhesives can form appreciable adhesion with tissues and have found clinical use in a variety of medical settings such as wound closure, surgical sealants, regenerative medicine, and device attachment. The advantages of tissue adhesives include ease of implementation, rapid application, mitigation of tissue damage, and compatibility with minimally invasive procedures. The field of tissue adhesives is rapidly evolving, leading to tissue adhesives with superior mechanical properties and advanced functionality. Such adhesives enable new applications ranging from mobile health to cancer treatment. To provide guidelines for the rational design of tissue adhesives, here, existing strategies for tissue adhesives are synthesized into a multifaceted design, which comprises three design elements: the tissue, the adhesive surface, and the adhesive matrix. The mechanical, chemical, and biological considerations associated with each design element are reviewed. Throughout the report, the limitations of existing tissue adhesives and immediate opportunities for improvement are discussed. The recent progress of tissue adhesives in topical and implantable applications is highlighted, and then future directions toward next-generation tissue adhesives are outlined. The development of tissue adhesives will fuse disciplines and make broad impacts in engineering and medicine.

Bioinspired tough gel sheath for robust and versatile surface functionalization.

Abstract: Sutures pervade surgeries, but their performance is limited by the mechanical mismatch with tissues and the lack of advanced functionality. Existing modification strategies result in either deterioration of suture's bulk properties or a weak coating susceptible to rupture or delamination. Inspired by tendon endotenon sheath, we report a versatile strategy to functionalize fiber-based devices such as sutures. This strategy seamlessly unites surgical sutures, tough gel sheath, and various functional materials. Robust modification is demonstrated with strong interfacial adhesion (>2000 J m-2). The surface stiffness, friction, and drag of the suture when interfacing with tissues can be markedly reduced, without compromising the tensile strength. Versatile functionalization of the suture for infection prevention, wound monitoring, drug delivery, and near-infrared imaging is then presented. This platform technology is applicable to other fiber-based devices and foreseen to affect broad technological areas ranging from wound management to smart textiles.

Reconfiguring confined magnetic colloids with tunable fluid transport behavior.

Abstract: Collective dynamics of confined colloids are crucial in diverse scenarios such as self-assembly and phase behavior in materials science, microrobot swarms for drug delivery and microfluidic control. Yet, fine-tuning the dynamics of colloids in microscale confined spaces is still a formidable task due to the complexity of the dynamics of colloidal suspension and to the lack of methodology to probe colloids in confinement. Here, we show that the collective dynamics of confined magnetic colloids can be finely tuned by external magnetic fields. In particular, the mechanical properties of the confined colloidal suspension can be probed in real time and this strategy can be also used to tune microscale fluid transport. Our experimental and theoretical investigations reveal that the collective configuration characterized by the colloidal entropy is controlled by the colloidal concentration, confining ratio and external field strength and direction. Indeed, our results show that mechanical properties of the colloidal suspension as well as the transport of the solvent in microfluidic devices can be controlled upon tuning the entropy of the colloidal suspension. Our approach opens new avenues for the design and application of drug delivery, microfluidic logic, dynamic fluid control, chemical reaction and beyond.

Injectable, Pore-Forming, Perfusable Double-Network Hydrogels Resilient to Extreme Biomechanical Stimulations.

Abstract: Biological tissues hinge on blood perfusion and mechanical toughness to function. Injectable hydrogels that possess both high permeability and toughness have profound impacts on regenerative medicine but remain a long-standing challenge. To address this issue, injectable, pore-forming double-network hydrogels are fabricated by orchestrating stepwise gelation and phase separation processes. The interconnected pores of the resulting hydrogels enable direct medium perfusion through organ-sized matrices. The hydrogels are amenable to cell encapsulation and delivery while promoting cell proliferation and spreading. They are also pore insensitive, tough, and fatigue resistant. When tested in biomimetic perfusion bioreactors, the hydrogels maintain physical integrity under prolonged, high-frequency biomechanical stimulations (>6000 000 cycles at 120 Hz). The excellent biomechanical performance suggests the great potential of the new injectable hydrogel technology for repairing mechanically dynamic tissues, such as vocal folds, and other applications, such as tissue engineering, biofabrication, organs-on-chips, drug delivery, and disease modeling.

Scaling Behavior of Fracture Properties of Tough Adhesive Hydrogels

Abstract: Tough adhesive hydrogels find broad applications in engineering and medicine. Such hydrogels feature high resistance against both cohesion and adhesion failure. The superior fracture properties may...

Ionotronic Tough Adhesives with Intrinsic Multifunctionality.

Abstract: Ionotronic hydrogels find wide applications in flexible electronics, wearable/implantable devices, soft robotics, and human-machine interfaces. Their performance and practical translation have been bottlenecked by poor adhesiveness, limited mechanical properties, and the lack of biological functions. The remedies are often associated with complex formulations and sophisticated processing. Here, we report a rational design and facile synthesis of ionotronic tough adhesives (i-TAs), which have excellent mechanical, physical, electrical, and biological properties and promise high scalability and translational potential. They consist of an interpenetrating network with high-density amine groups and highly mobile chains, which enable intrinsic adhesiveness, self-healing, ionic stability, cytocompatibility, and antimicrobial functions. The i-TAs in both pristine and swollen states possess high toughness, stretchability, and strong adhesion to diverse substrates such as tissues and elastomers. The superior mechanical performance is achieved simultaneously with high ionic conductivity and stability in electrolyte solutions. We further demonstrate the use of i-TAs as wearable devices, strain sensors, and sensory sealants. This work is expected to open avenues for new ionotronics with novel functions and stimulate the development and translation of ionotronics.

Stimulation Modulates Adhesion and Mechanics of Hydrogel Adhesives.

Abstract: The ability to modulate the adhesion of soft materials on-demand is desired for broad applications ranging from tissue repair to soft robotics. Research effort has been focused on the chemistry and architecture of interfaces, leaving the mechanics of soft adhesives overlooked. Stimuli-responsive mechanisms of smart hydrogels could be leveraged for achieving stimuli-responsive hydrogel adhesives that respond mechanically to external stimuli. Such stimuli-responsive hydrogel adhesives involve complex chemomechanical coupling and interfacial fracture phenomena, calling for mechanistic understanding to enable rational design. Here, we combine experimental, computational, and analytical approaches to study a thermo-responsive hydrogel adhesive. Experimentally, we show that the adhesion and mechanical properties of a stimuli-responsive hydrogel adhesive are both enhanced by the application of a stimulus. Our analysis further reveals that the enhanced adhesion stems from the increased fracture energy of the bulk hydrogel and the insignificant residual stress on the adhesive-tissue interface. This study presents a framework for designing stimuli-responsive hydrogel adhesives based on the modulation of bulk properties and sheds light on the development of smart adhesives with tunable mechanics.

Fracture Mechanics of Human Blood Clots: Measurements of Toughness and Critical Length scales

Abstract: Blood coagulates to plug vascular damage and stop bleeding, and thus the function of blood clots in hemostasis depends on their resistance against rupture (toughness). Despite the significance, fracture mechanics of blood clots remains largely unexplored, particularly the measurements of toughness and critical length scales governing clot fracture. Here, we study the fracture behavior of human whole blood clots and platelet-poor plasma clots. The fracture energy of whole blood clots and platelet-poor plasma clots determined using modified lap-shear method is 5.90{+/-}1.18 J/m2 and 0.96{+/-}0.90 J/m2, respectively. We find that the measured toughness is independent of the specimen geometry and loading conditions. These results reveal a significant contribution of blood cells to the clot fracture, as well as the dissipative length scale and nonlinear elastic length scale governing clot fracture.