Plowing Microgrooves For The Fabrication Of Flexible Transparent Conductive Films

Flexible transparent conductive films(FTCFs)are critically important for the emerging flexible electronic devices.The FTCFs are widely used in flexible solar cell,lightemitting diodes,supercapacitor,touch panels,smart windows and so on.At present,the widely used transparent conductive films(TCFs)are mainly fabricated from indium tin oxide(ITO).However,due to the scarce resources of indium,the cost of TCFs fabricated by ITO is expensive.Moreover,the TCFs fabricated by ITO are mechanically brittle and difficult to meet the requirements of flexible electronic devices.Therefore,many alternative materials to ITO have been developed in recent years.Among them,metal gratings is an excellent ITO alternative material due to its excellent performance and low cost.However,there are great challenges to fabricating FTCFs with metal gratings in a simple and economical method.In this paper,a roll-to-roll(R2R)plowing equipment based on the plowing processing method has been designed.Subsequently,the microgrooves were continuously plowed on the surface of polycarbonate(PC)substrate.Then,nanoconductive silver paste were filled into microgrooves by blade coating,and the FTCFs with parallel conductive silver paths was continuously fabricated.The main research contents and conclusions are as follows:(1)Numerical simulation of microgrooves fabricated by plowing processThe plow was assembled by a series of razor blades with well aligned sharp tips.Then,it was used to plow microgrooves on the surface of polymer films.The plow and PC film were separately modeled using Solidworks software.Finally,the plowing processes of microgrooves were simulated in DEFORM-3D software.The influence of plowing speed and plowing depth on the microgroove morphology were investigated.The results show that the morphology of microgrooves is mainly influenced by the plowing depth.The depth and width of the microgrooves increase linearly with the increasing plowing depth.Meanwhile,lips appear on both margins of the microgrooves.The height of the lips increases with the increase of the plowing depth.This result provides an experimental basis for the preparation of microgrooves by continuous plowing process on the surface of polymer films.(2)Fabrication of flexible transparent conductive films with parallel conductive micro pathsThe microgrooves were continuously fabricated on the surface of PC substrates by R2R plowing equipment.Then,the nanoconductive silver paste were filled into the microgrooves by blade coating.Finally,the FTCFs with parallel conductive silver paths were successfully fabricated.The influence of applied loading on the microgroove morphology was systematically investigated.The experimental results show that the depth and width of the microgrooves increase linearly with the increasing applied loading.Meanwhile,lips appear on both margins of the microgrooves.The height of lips increases linearly.The influence of the silver paste sintering time on the conductivity of the FTCFs was investigated after scraping the silver paste into the microgrooves.The results show that the square resistance decreases rapidly with increasing sintering time and then remains constant.The lowest square resistance of 3.1 Ω/sq is obtained at 22 min,and the transmittance of the FTCFs is 78.2%.Then,the fabricated FTCFs was sandwiched between two pieces of polyvinyl butyral film(PVB)by vacuum-assisted hot pressing to fabricate trilayered film.The transmittance of the trilayered film reaches84.2%.Next,the mechanical flexibility of the trilayered film is systematically investigated through inner and outer bending and cyclic fatigue tests with the resistance monitoring.The results show that the trilayered film has good flexibility.Subsequently,the trilayered film was fabricated as a flexible transparent heater.The electrical heating performance was characterized.The results show that it has good electrical heating performance.Finally,a flexible capacitive keyboard was prepared by the FTCFs with parallel conductive silver paths.It was successfully used for wireless control of personal electronic devices in combination with a human-machine interface system.This study provides a promising strategy to fabricate high performance FTCFs via a continuous,cost-effective,and environmental friendly way.