Design Of BioInspired Nanocellulose-Based Smart Actuator

Energy shortages,resource shortages,environmental pollution and other issues constrain the world's sustainable development,and it is urgent to seek new,green,environmentally friendly and renewable raw materials to promote the development of smart materials.Inspired by the structural characteristics and biological functions of natural materials,bionic materials are developed as new driven materials that can automatically perceive changes in the external environment and make sensitive responses,which possess the characteristics of intelligent energy-saving.It is the fourth generation of materials after natural materials,synthetic polymer materials and artificial design materials.Nanocellulose is one of the most promising and developmental nanomaterials because of its wide source,abundant reserves,biodegradability,biocompatibility,high strength,high specific surface area and rich functional groups.it will be designed as a smart material to play an important strategic role in promoting the sustainable development of the national economy.In this study,inspired by the automatic opening and closing phenomenon caused by the asymmetrical expansion/contraction structure of pine cone scales under natural conditions,nanocellulose with the nanoscale fine structure,high aspect ratio and high mechanical properties was obtained from Amorpha fruticosa.And by subtly designing functional groups and layered film-forming structures,bionic intelligent materials with singlelayer structure and sensitive humidity response were built.On this basis,the nano-cellulose layered film is used as the base layer,and the layered graphene layer and the cellulose acetate layer are respectively built on it,and then the humidity-driven multifunctional bionic intelligent material and the solvent-driven bionic intelligent material are designed and constructed.Through the proof of concept of these driven materials in the fields of smart fabrics and gas sensors,it provides a conceptual solution for designing intelligent materials with abundant biomass resources,and has an important strategy significance for building a green and sustainable intelligent society in the future.The results show that:(1)Inspired by the phenomenon of automatic opening/closing of pineal scales in nature,nanocellulose with high aspect ratio(> 1000)was prepared by TEMPO oxidation method.Based on this building material,intelligent materials with sensitive humidity response(5s),large active deformation(> 180 degrees)and high reversible cycle times(10000 times)were successfully designed.Applying this kind of humidity-responsive driven material to smart clothes for concept verification can not only realize the function of intelligent cooling anddehumidification,but also have good permeability,transparency(91.7%)and mechanical strength.It is one of the ideal materials for building smart clothes.(2)In order to further endow nanocellulose-based intelligent materials with multifunctional properties,nano-titanium dioxide was doped in nanocellulose to effectively endow the intelligent materials with bactericidal and purification functions,and the bacteriostatic circles of 4 mm and 3 mm were formed in the Petri dishes of Escherichia coli and Staphylococcus aureus,respectively.On this basis,composite layered graphene can endow intelligent materials with the functions of electrothermal effect and photothermal behavior.And under 4.5V voltage,the intelligent material can be rapidly heated to nearly 10°C in 120 s,and the temperature can be raised by 15°C in 30 min under illumination;At the same time,the intelligent material also has a sensitive humidity response(8s).Similarly,the multifunctional smart material is conceptually applied in the field of smart clothes,which can not only make clothes automatically dissipate heat and moisture,but also provide energy for the human body and provide the function of sterilizing and cleaning the skin in a timely manner,which provides a conceptual solution for the future personal thermal management system in the field of fabrics.(3)In order to design intelligent materials with multiple stimulus responses,the nanocellulose layered membrane and cellulose acetate membrane were compounded to build an intelligent material for solvent response,which can effectively sensitize different gases(acetone,ammonia,humidity,etc.)with large response range(> 180 degrees),high sensitivity(3.5s),and good stability(120s bending constant).The more sensitive response and the greater the bending degree of the intelligent materials,the higher the concentration of solvent.It can be used as a gas sensor to monitor the safety of ambient gas in real time,which provides a concept verification for the design of new gas sensors.