Room-temperature Plasma-jet For The Mask-free Fabrication Of Flexible Devices

Flexible and wearable devices,such as flexible sensor,flexible touch panel and flexible electronic skin,are changing and enriching our daily life.Recent advances in wireless technologies,low-power electronics,and in the domain of digital health are driving innovations in wearable devices at a tremendous pace.The flexible and wearable device market will reach US$20.6 billion in 2018.Flexible transparent,conductive films and flexible micro-supercapacitors are both important components in flexible devices.However,developing novel and facile methods for the fabrication and processing of both flexible transparent conductive films and flexible micro-supercapacitors remains a great challenge.In this dissertation,we use a home-made atmospheric pressure pulsed plasma-jet for the nanowelding of silver nanowire junctions,the patterning of silver nanowire thin films,the fabrication of carbon-based all-solid-state micro-supercapacitors,and the fabrication of high-performance micro-supercapacitors based on silver nanowire/carbon material composite.More details are as follows.?1?Nanowelding of silver nanowire junctions via mask-free ambient cold plasma-jet treatment.Silver nanowire thin film is a promising candidate to replace traditional indium tin oxide as flexible and transparent electrodes for optoelectronics applications.To date however,the widespread application of AgNW thin film is limited by the high junction resistance between individual AgNWs,and improving the point contacts between AgNWs remains a great challenge.In this work,a novel and facile method for rapid nanowelding of silver nanowire junctions via mask-free cold plasma jet treatment in ambient conditions is demonstrated.The local electric field in and around the plasma jet brings about joule heating in AgNWs,which plays a critical role in the nanowelding technique.After plasma-jet treatment,the junctions of AgNWs are welded together.The nanowelded AgNW thin film shows enhanced electrical property,enhanced mechanical property,and almost unchanged optical transmittance.The nanowelding technique are easy operated,time-saving and cost-effective.?2?Patterning of silver nanowire thin films via mask-free ambient cold plasma-jet scanning.The widespread application of AgNW thin film as flexible and transparent electrodes is limited by the lack of facile patterning techniques.Developing novel patterning techniques remains a major challenges.In this work,a novel and facile method for patterning of silver nanowire thin films via mask-free plasma-jet scanning is demonstrated.After the plasma-jet patterning treatment,the AgNWs in the treated section are etched and transformed into separated large particles.The etched sections in the AgNW film are non-conductive and present high optical transmittance.Various kinds of patterns can be produced via this patterning technique.The patterning technique are easy operated,cost-effective and readily scalable.Moreover,a simple LED circuit certifies the suitability of the patterned AgNW electrodes for flexible electronic devices,indicating that the cold plasma-jet patterning technique is a promising candidate for the processing of AgNW thin film in optoelectronics applications.?3?Carbon-based flexible micro-supercapacitor fabrication via mask-free ambient micro-plasma-jet etching.Micro-supercapacitors?MSCs?are attracting significant interest owing to the advantages of small volume and easy integration into circuits of micro devices.Carbon-based materials are extensively explored as electrodes materials for micro-supercapacitors.Photolithography with subsequent etching is the most widely used patterning technique for carbon-based micro-supercapacitors fabrication.However,this technique suffers from complicated operation,high cost,and photoresist contamination due to the involvement of conventional lithographic techniques and the employment of masks.As a result,this technique is awkward for simply building cost-effective and high-performance devices for commercial applications.In this work,I demonstrate a general and facile method to fabricate all-solid-state flexible micro-supercapacitors with micropatterned multi-walled carbon nanotube?MWNT?electrodes via mask-free micro-plasma-jet etching in ambient conditions.Localized pulsed plasma jet etches the MWNTs rapidly and produces the interdigitated electrode patterns by scanning.This facile patterning technique is not only cost-effective and readily scalable,but also free from photoresist contamination.The fabricated MSCs exhibit the expected electrical double layer behavior and have a stack capacitance of 2.02F cm^-3 at a scan rate of 10 mV s^-1.Moreover,the MSCs show stable performance under repeated bending,with retention of 98.2%of capacitance after 600 bending cycles.Furthermore,other carbon-based materials,such as single layer graphene and thin film of reduced graphene oxide,can also be etched into different kinds of micro patterns by this patterning technique which suggests that this patterning technique is a promising candidate for the fabrication of carbon-based flexible electronic devices in the future.?4?Silver nanowires as the flexible current collector for in-plane high-performance micro-supercapacitor fabrication.Current collectors are important components of all-solid-state flexible micro-supercapacitor?MSC?devices.Up to now,titanium-gold is most widely used as the current collector for in-plane MSC fabrication.However,the fabrication processes of titanium-gold based in-plane MSCs,which require the patterning of the current collector first and the subsequent patterning of the active material with the assistance of photoresist and mask,are high-cost and especially complicated.Moreover,the photoresist used in the fabrication processes affects the properties such as active surface and porous structure of the active materials.Therefore,more efforts must be devoted to developing novel current collectors for flexible in-plane MSCs as well as simplifying the present two-step patterning method for in-plane MSCs fabrication.In this work,I use silver nanowire?AgNW?as the current collector to fabricate all-solid-state flexible in-plane MSC with micropatterned carbon nanotube?CNT?/AgNW electrodes via one-step patterning of both the active material and the current collector.An atmospheric pressure pulsed micro-plasma-jet is used to realize the one-step mask-free patterning and produce the interdigitated CNT/AgNW electrodes.Remarkably,the fabricated MSC with AgNW current collector presents good flexibility as well as excellent rate capability.Moreover,the performances including cyclic stability,equivalent series resistance,relaxation time and energy/power densities of the CNT/AgNW based MSC are significantly improved with the presence of AgNW current collector.This work provides a facile route for the fabrication of current collector contained high-performance flexible in-plane MSCs.