The latest progress of bonding theory at home and abroad in 2025

This article is from the wechat official account of “Bonding”

The latest advancements in bonding theories both at home and abroad are mainly reflected in the deepening of traditional theories, the exploration of bionic mechanisms, breakthroughs in dynamic reversible bonding technologies, and innovations in material modification. The following summarizes the key progress in recent years from multiple perspectives:

01 Dynamic Reversible Bonding and Intelligent Responsive Materials

Light-controlled intelligent bonding: The photocontrolled hydrogel material developed by the team from the Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, by embedding photothermal nanoparticles (such as iron (III) oxide), uses infrared light to trigger conformational changes in surface molecules, achieving rapid and reversible switching of adhesion force (from high adhesion state 9.86 kPa to low adhesion state 0.26 kPa). Its mechanism is similar to the adhesion/desorption mechanism of gecko feet. Through the dynamic response of temperature-sensitive groups (such as N-isopropyl acrylamide), combined with molecular migration mediated by water molecules, it achieves resister-free recycling.

Thermal response and strain-induced bonding: The polyurethane (PUD) adhesive developed by Sichuan University enhances cohesion through strain-induced crystallization and improves interfacial bonding strength by the high activity of catecholic acid side chains, achieving an adhesion strength of 11.37 MPa and a de-adhesion force of 10.32 kN/m. Its dynamic hydrogen bond network supports cyclic bonding and on-demand debonding, making it particularly suitable for temporary assembly requirements in complex environments.

02 Interface Optimization and Molecular Design

Bionic interface structure: Inspired by gecko bristles and tree frog mucus, researchers have increased the interface contact area by simplifying bionic structures (such as nanoscale bristles arrays or micrometer-scale grooves). For instance, the Janus viscoelastic hydrogel barrier developed by Xi ‘an Jiaotong University achieves asymmetric adhesion (with the adhesive surface firmly bonded to the tissue and the non-adhesive surface free) through a layered hydration strategy, effectively preventing postoperative adhesion. This design combines dynamic borate ester bonds and methylacrylylated polysaccharides, optimizing the interfacial mechanical compatibility. Molecular chain functionalization: Introducing active groups such as catechol and epoxy soybean oil (ESO) into the polyurethane adhesive to enhance the chemical bond with the substrate. For instance, the dual cross-linking modification of waterborne polyurethane with epoxy soybean oil and siloxane (KH550) significantly enhances water resistance and peel strength, while regulating the microphase separation structure and optimizing the overall performance.

03 Environmentally friendly and Sustainable Bonding Technology

Development of bio-based materials : Henkel has launched Loctite HB S ECO and CR 821 ECO bio-based polyurethane adhesives, with a bio-based raw material ratio of 63% to 71%, reducing carbon dioxide emissions by more than 60%. This type of adhesive demonstrates high durability in load-bearing wood structures, promoting the development of green buildings.

Waterborne polyurethane technology: By replacing solvent-based adhesives with environmentally friendly crosslinking agents (such as carboxylic acid-based anionic systems), VOC emissions are reduced. Research shows that the viscosity of waterborne polyurethane is independent of molecular weight and is suitable for bonding automotive interior parts. However, its water resistance still needs to be further improved through nano-fillers (such as montmorillonite) or cross-linking modification.

Interdisciplinary Integration of 04 Bonding Mechanism

The concept of “force medicine” proposed by the team from Xi ‘an Jiaotong University introduces mechanical regulation into the design of biomaterials. For instance, viscoelastic hydrogels achieve adaptive adhesion at dynamic interfaces by simulating organ movement patterns such as cardiac contraction and intestinal peristalsis, thereby reducing the risk of postoperative adhesion.

Digitalization and intelligent control: Digital indirect bonding technology (such as the Suresmile system) combined with CAD/CAM technology optimizes the positioning accuracy of brackets and reduces adhesive residue. In the field of dentistry, the fluidity of adhesives is controlled through the design of overflow holes and the optimization of abutment geometry (such as hollow through abutments) to reduce the risk of residue.

05 Deepening and Challenges of Traditional Theories

New Insights into the Weak boundary Layer Theory: Research has confirmed that interface failure often stems from the presence of a weak boundary layer (such as low-molecular impurities in polyethylene), and surface treatment (such as plasma cleaning) can significantly enhance the bonding strength. For instance, when polyurethane adhesives are used in automotive windshields, they need to be combined with a primer to treat non-porous surfaces to eliminate weak boundary effects.

The synergy of adsorption and diffusion theories: For polymer substrates, the combination of adsorption theory (intermolecular forces) and diffusion theory (molecular chain entanglement) is used to explain the bonding behavior of high-performance adhesives. For instance, strain-induced crystallization of polyurethane achieves a balance between strength and toughness by enhancing the bulk strength while maintaining dynamic interfacial bonding.

Summary and Outlook of 06

The current research trends in bonding theory focus on dynamic response, bionic design, environmentally friendly materials, and interdisciplinary integration. Future directions may include:

Multi-stimulus-responsive materials: Developing smart adhesives with coordinated regulation of multiple factors such as light, heat, and pH;


The combination of nanotechnology and biotechnology: Utilizing nano-fillers (such as carbon nanotubes) to enhance interfaces, or biomimetic mucus secretion mechanisms to improve environmental adaptability;

Sustainability evaluation system: Establish full life cycle assessment standards for bio-based adhesives and promote industrial application.