Fabrication And Wettability Tuning Of Smart Responsive Biomimetic Functional Surfaces

Nature is a school for engineers to develop advanced materials and functional systems.For instance,inspired by the self-cleaning effect of lotus leaves,biomimetic superhydrophobic surfaces are of great value for a variety of applications such as pollution resistant,anti-corrosive,ice-proof,and oil-water separation.The special interface property is determined by two facets,surface micro-/nanostructures and material surface energy.In recent years,well-designed responsive materials enable functional surface to alter their surface properties in response to external stimuli.With the capability of reversible and dynamic control,responsive biomimetic functional surfaces have revealed great potential for intelligent applications,and have emerged as an active research field.However,there are still many problems in the regulation of responsive functional surfaces,such as the controllability of micro-/nanostructures,response and recovery time,the achievable wetting states,and biocompatibility,which limit their practical implementation.To address these issues,this thesis mainly concentrates on the efficient tuning of biomimetic ultrahydrophobic wetting states.Pneumatically responsive superhydrophobic surfaces have been developed to realize the exquisite control over surface structure and dewetting properties,the mechanism of wettability transition have been carefully studied as well,this work would provide a new strategy for tuning surface properties.Wearable smart superhydrophobic surface have been utilized to skin,wettability control have been achieved by simple body motions,as an effort to extend the application of smart surfaces.The researches in this thesis are listed as follows:1.Fabricating pneumatically responsive superhydrophobic surfacesThe reported strategies for wettability modulation mainly originate from a gradual change in surface chemistry and surface energy.These processes generally require a long response time and have special restriction on materials.During the actuations,the surface structure is usually static or slight changed.In fact,surface structural reconfiguration enables rapid and dynamic modulation of surface properties in a direct manner.However,the realization of large-area control of micro-/nanostructures is difficult,still facing technical challenges.In this thesis,we have designed and constructed pneumatically responsive smart functional surfaces to achieve this goal.(1)A protuberant micro-air-sac network has been developed based on a common elastomer via a stretching-assisted mismatch-bonding process.The micro-air-sacs were uniform and airtight without local clogging.(2)The prepared surface could undergo rapid,reversible,and large-amplitude deformation.And the pneumatic performance was demonstrated to be stable.Dynamic modulation of surface structure and wetting states was achieved by selective surface modification.The pneumatic surface could be thus switched between lotus-leaf-like and rose-petal-like dewetting states on demand.(3)By observing and analyzing the solid-liquid interface,we proposed wetting models for the inflated and deflated states.According to the classical wettability theories and experimental parameters,theoretical values of surface contact angles(CAs)in the two states were calculated,consistent with the experimental results.(4)Based on the pneumatic transition between the two contrasting states,the smart surface was implemented to capture and release droplets.2.Fabricating smart superhydrophobic elastomer skinsConsiderable efforts have been devoted to extending the application fields of functional surfaces.Recently,superhydrophobic surfaces are promising for wearable applications.However,regulating processes pose a potential risk to human health,such as the use of UV irradiation,toxic chemicals,and high temperature,which make them unfit for wearable applications.In this thesis,we have fabricated soft stretchable elastomer skins,and realized the wettability control by body motions.(1)According to skin textures,direct laser writing(DLW)technology was employed to generate microstructures on the elastomer surface.The skin-like surface could make a conformal contact with skin.By tuning the laser power,the secondary micro-/nanostructures could be finely modulated to achieve superhydrophobicity.(2)Mechanical stretching enabled a rapid,reversible and continuous control over surface topography and wettability.The controllable actuation is mild and user-friendly.The ability to switch wetting states allowed the functional surface to handle multiple droplets in parallel.(3)The active surface could be further applied to the joints of fingers and operate as a droplet manipulator under finger motions without requiring energy supply or external appliance.The dynamic tuning of wetting properties is integrated into the design of skin-like wearable surfaces,making responsive functional biomimetic surfaces promising for developing smart skin.In summary,we have fabricated pneumatically responsive superhydrophobic surfaces.The surface micro-/nanostructures and wettability could be controlled rapidly and reversibly.In this regard,we demonstrated a novel pneumatic smart surface.Moreover,the functional surface could mimic both “lotus effect” and “petal effect”,the on-demand wettability transition allowed it to handle droplets.Meanwhile,we have fabricated smart elastomer skins by one-step laser processing.The prepared surface was skin-conformable,superhydrophobic,and capable of switching surface wettability under body motions.In this way,the application of responsive functional surface is extended to wearable uses.