Research On Patterning Method Of Nanocracks On Polyimide Substrate

Nanocrack-based sensors have high sensitivity and have broad application prospects in physiological signal collection,human-computer interaction and other fields.The performance of nanocrack-based sensors is affected by the pattern of nanocracks,and realizing the precise and controllable distribution of nanocracks has important scientific significance and practical application value.Therefore,researchers have proposed various nanocrack patterning methods,such as defect-induced method,thin-film-assisted method,curvature-controlled method,and photolithography-assisted method.However,in these nanocrack patterning methods,most of the substrate materials used are polydimethylsiloxane(PDMS),polyurethane acrylate(PUA)and other materials with low Young's modulus,so that the response speed of nanocrack-based sensors fabricated on such substrates is greatly limited.Polyimide(PI)is a commonly used flexible substrate,and it has a higher Young's modulus.Nanocrack-based sensors on PI substrates can achieve rapid response to external input.However,the method for patterning nanocracks on PI substrates remains to be developed.In order to realize the patterning of gold nanocracks on PI substrate,a stretchability differences nanocrack patterning(SDn CP)method is firstly proposed.By using the patterned chromium film as the crack guiding layer,a PI substrate-chromium intermediate layer-gold film structure was fabricated.Due to the obvious difference in stretchability between the chromium film and the gold film,nanocracks were generated at specific positions in the gold film after stretching the PI substrate,thereby realizing the patterning of nanocracks.In order to simplify the generation process of gold nanocracks,an adhesion differences nanocrack patterning(ADn CP)method is further proposed,and explored.It provides technical reserves for the research on the next generation nanocrack patterning of metal thin films on PI substrates with no crack guide layer.The factors affecting the patterning of nanocracks on PI substrates were studied.Based on the reported mechanism of nanocrack generation,the process of nanocrack generation based on SDn CP method was analyzed.By analyzing the rule of nanocrack generation,it is suggested that the thickness of the chromium intermediate layer,the pre-strain of the PI substrate,the thickness of the gold film,and the pattern of the chromium intermediate layer affect the patterning quality of nanocracks on PI substrate.The experimental results showed that the generation of nanocracks on the gold film was guided by the chromium intermediate layer.The smaller the pre-strain of the PI substrate,the narrower the width of the chromium intermediate layer,and the density of gold nanocracks on PI substrates is smaller.Moreover,the SDn CP method is universal.Based on the proposed nanocrack patterning method on PI substrate,a nanocrack-based strain sensor on PI substrate was further fabricated and tested.The results showed that the prepared nanocrack-based strain sensor had merits of fast response,achieving a response time less than 16 ms.