Advances of carbon nanotube adhesive materials

Adhesion pertains to a widely observed phenomenon in the surrounding environment, wherein two interfaces establish a connection through surface interaction forces upon contact. Adhesion offers distinct advantages over mechanical fastening and welding, such as uniform stress distribution, cost-effectiveness, easy bonding, and flexibility in the shape of the connection interface. As scientific and technological advancements continue to unfold, adhesion is anticipated to supplant traditional connection methods like mechanical fastening and welding, emerging as a mainstream approach with potential applications in various fields, including biomedicine and electronic devices. For instance, the utilization of adhesive materials instead of straps to secure wearable electronic devices on the human body can enhance comfort. Adhesive patches possessing properties suitable for direct attachment to the skin or heart can greatly improve convenience and usability. Similarly, substituting welding with adhesive materials for device fixation on circuits can significantly enhance assembly efficiency. Consequently, the development of adhesive materials represents a crucial area of research for the future. Adhesive materials can be classified into several types based on their components, including polymer adhesives, hydrogel adhesives, and adhesive materials containing carbon nanotubes (CNTs). Among these, CNTs stand out due to their exceptional mechanical properties, making them an ideal constituent for the preparation of adhesive materials. On one hand, the heightened stiffness of CNTs prevents them from collapsing under pressure. On the other hand, their ultra-high aspect ratio (ranging from 10(3) to 10(5)) reduces the effective elastic modulus, enabling full contact with the substrate and displaying excellent adhesion properties. Compared to polymers and hydrogels, the utilization of CNTs as fundamental components of adhesive materials offers numerous advantages, including, but not limited to: (1) Exceptional mechanical properties, ensuring structural integrity and durability during use; (2) superior and stable physical and chemical properties, enabling their deployment in extreme environments (e.g., high temperature, low temperature); and (3) excellent electrical and thermal conductivity, along with the potential for multifunctional material development (e.g., conductive adhesives, thermal adhesives). Since the initial investigation of the adhesion between CNT arrays and silicon probes in 2005, CNT adhesion has garnered considerable attention in the scientific community and has become an important research direction in the field of adhesives. However, there exists a scarcity of literature summarizing the recent advancements made in the past five years. This review aims to provide a formal and scientific account of the subject matter. Firstly, the review presents an introduction to the adhesion mechanism of CNTs based on microscopic and simulation studies. Secondly, it examines macroscopic performance studies, encompassing aspects such as regulation of structural parameters and special structural designs. Thirdly, the review demonstrates the potential applications of CNT adhesion in the fields of electronic devices, biomedicine, and energy storage. Lastly, a detailed discussion on the advantages and disadvantages of CNT adhesion materials compared to polymer adhesives and hydrogel adhesives is provided, along with a prospective outlook on the future development direction of CNT adhesion. This comprehensive review offers an in-depth understanding of the current state of CNT adhesion research and provides valuable insights for future investigations in the field.