Synthesis And Property Study Of Bio-inspired Carbon Nanotube Array Adhesive

Geckos,the world's most famous climbers,are capable of attaching and detaching their adhesive toes in milliseconds while running with apparently reckless abandon on various surface,regardless of the surface roughness,cleanliness and inclination angle.The secret of their super adhesive ability lies in the hierarchical branched hairs uniformly distributed on the soft toe pad.A micro-sized single seta is split into hundreds of nanometer spatula,which could make intimate contact with nearly any surface,translating weak Van der Waals(vdW)forces into humorous adhesive strength.Therefore,it is necessary to develop a gecko-inspired adhesive with supreme adhesive performance through mimicking the hierarchical structure of geckos,which could help optimizing the performance of three dimensional-terrain obstacle free(TDOF)gecko-inspired climbing robots and adhesive facilities working in space environment.Vertical aligned carbon nanotube array(VACNT)can be synthesized through chemical vapor deposition through a self-assembly mode,which exibit great mechanical property and the similar micro-nano size scale with gecko hairs.VACNT can make intimate contact with most surfaces,generate enough vdW forces and strong adhesion.Therefore,it is a competitive choice for making gecko-inspired adhesive.In addition to its electrical,optical,thermal conductivity and chemical stability,VACNT also show stable properties even under extreme conditions,such as high/low temperature and vacuum environment.The excellent performance of VACNT make it potential candidate of making gecko-inspired adhesive used for climbing robots and facilities used in space environment.This dissertation manly focuses on the preparation technology and transfer method of VACNT,the test methods for macro-scale adhesive property of VACNT,the height-controlled growth methods of VACNT and its mechanism,the pattern-designed VACNT with super-hydrophobicity and self-cleaning ability,the adhesive property of VACNT and its composite under vacuum and thermal vacuum environment.The chemical vapor deposition growth method of VACNT was developed and the height of VACNT reached 400-800?m.The influence of major processing parameters and growth mechanism of CVD process were also discussed.Using a thermal oxidation process,a versatile transfer method for transferring VACNT onto flexible polymer substrates was developed,which help improving the interfacial bonding strength nearly 13-15 times.In addition,the transferred flexible VACNT also exhibit danymic self-cleaning ability.A macro-scale adhesive strength test system was established and the results show that the adhesive strength of transferred VACNT was achieved 49N/cm2 and the ?* was nearly 1.225,which was improved obviously compared with VACNT grown on Si substrate.The multifunctional material adhesion test platform(IBSS-2,NBIT,Nanjing,China)was used to accurately analyze the attach-detach behavior of VACNT and the shear/normal adhesive strength was 6.02N/cm2,25.55 N/cm2 respectively.The ultrafast growth of super-long VACNT(7mm)was achieved by ethanol-assisted two-zone CVD process,and the maximum growth rate was nearly 280?m/min.Using the carbon by-product deposited on the inner wall of furnace tube as the new carbon source,super-short VACNT(<200?m)was also synthesized and exhibited enhanced adhesive strength(61.25N/cm2,?* was nearly 1.53).Through mimicking the lamella and seta array structure of the gecko toe pad,patterned VACNT with different geometrical parameters were designed and fabricated combined photo-lithography and CVD process.Both patterned VACNT showed super-hydrophobicity(contact angle >150°,rolling angle<5°)as well as self-cleaning property.Vacuum and thermal vacuum of space environment was simulated for testing the frictional attachment-detachment property and adhesive strength of VACNT and PDMS/CNT composite.Results show that in vacuum environment,VACNT and PDMS/CNT exibited a similar frictional attachment-detachment behavior compared with those at atmospheric environment.Under vacuum environment,the frictional adhesive strength of PDMS/CNT was improved whereas VACNT has no obvious change.Both of them have good adhesive stability.In thermal vacuum environment,the normal and shear adhesive strength can be maintained over 30 minutes for both VACNT and PDMS/CNT(0.5N/cm2).