Rapid Thermal Nanoimprint And Study On Amphiphobic Surfaces

Nanoimprint lithography(NIL)has been widely studied due to its low cost,high through output and high resolution since it was developed in 1990s.Nowadays,NIL has been widely used in fabricating many kinds of micro/nano applications.There are two fundamental types of NIL:thermal NIL(T-NIL)and ultraviolet NIL(UV-NIL).Various heating methods including hot gas heating,infrared radiation(IR)heating,ultrasonic heating,and electric resistive heating have been studied.Hot gas heating requires complex facilities and is not very effective in heating the imprint materials.Ultrasonic heating is limited due to the extremely small heating area.IR heating cannot work after the imprint apparatus closes.It is therefore limited to preheating applications.Electric resistive heating can overcome these limitations,but it usually heats the whole imprint tool along with the imprint materials.A large amount of energy is wasted,which also results in a slow rate of heating and cooling.However,because it takes too much time to heat up and cool down the whole system,thermal nanoimprint lithography has relatively low work efficiency.To solve the problem,we introduce a novel induction heating method into the imprint process,instead of the traditional heating approaches.By applying a high-frequency alternating current(AC)through a customer-made induction coil,a rapidly alternating magnetic field penetrates the nickel mold,generating electric currents inside the mold called eddy currents.The eddy currents flow through the resistance of metal and are heated by Joule heating.Moreover,for nickel as the ferromagnetic metal,heat can also be generated by magnetic hysteresis losses.Hence,the nickel mold can be heated up at a very high speed.And once the external alternating current is cut off,heating process is terminated and the temperature of the nickel mold will fall fast due to its small thermal capacity,thus providing a high heating and cooling efficiency rate for the thermal nanoimprint process.In this thesis,the heating efficiency and cooling efficiency were tested by replicating nanoholes with a pitch of 600nm,diameter of 300nm and depth of 250nm onto poly(methyl methacrylate)(PMMA)sheets.As a result,time consumed in nanoimprint can be reduced from tens of minutes to 5 minutes or less.The uniformity test was also carried out.It was shown that the edge region and the central region of nickel mold can be synchronously heated which the temperature difference is less than 5%during the imprinting process,which is beneficial to the preparation of a large-area uniform structure.The effects of the imprint parameters like pressure and temperature on the depth of imprinted nanoholes were measured during the thermal nanoimprint process.Furthermore,the manufacture of nickel mold was introduced.The nickel mold which is transformed by the composite template has the advantages of high mechanical strength,good toughness and long service life.All the results show that the electromagnetic induction heating nanoimprinting device has realized the rapid replication of nanostructures and is expected to be an effective means for mass production of micro/nanostructure devices.On the other hand,in the fields of industrial production,medical and health,and national defense,more attention has been paid to the manufacture of robust superoleophobic-superhydrophobic surfaces with the growing demand for antibacterial,self-cleaning and excellent wettability solid surfaces.The wettability of solid substrates is usually governed by their surface free energy and surface geometrical structures.In this thesis,nanoimprint lithography,atomic layer deposition and 4pattern transfer techniques were used to fabricate the overhang structure onto Corning GG3 glass and the anti-sticking layer with low surface free energy was grown on the surface of the sample with 1H,1H,2H,2H-perfluorodecyltrichlorosilane.The effects of the etch parameters like time,RF power and bias power on the aspect ratios of nanoholes were measured.It was introduced that with the increase of the aspect ratio of the structure,the hydrophobic properties and oleophobic properties of the glass surface were improved.Meanwhile,it was proved that the hydrophobicity and oleophobic performance can be improved after preparing overhang structure at the top of nanoholes with different aspect ratios.The water contact angle is increased by 30.40°on average and the oil contact angle is increased by 21.6°on average.Furthermore,we fabricated overhang structure on the silica layer by growing silicon dioxide on GG3 glass with ultraviolet nanoimprint lithography and dry etch.We tested that the prepared sample has shown superhydrophobic-high oleophobic performance and it is expected to further enhance the oleophobic performance if the subsequent use of material with higher mechanical strength instead of PMMA is achieved.