Fabrication And Properties Of Cellulose Paper-Based Energy And Sensing Devices

As the resource shortage and environmental pollution become more serious,efficient conversion of clean energy and the development of green sensing devices need to be urgently solved.Lignocellulosic resources,with many advantages such as rich reserves,renewable,biodegradable,etc.,have potential applications in the preparation of environmentally friendly advanced material and functional device.In this study,a series of novel paper-based flexible energy and sensing devices were designed and constructed through facile and green methods;the devices'properties and working mechanism were studied,and their applications in energy conversion and strain/pressure sensing were achieved.This promoted the sustainable development of green energy and wearable electronics.The main research work of the thesis is as following:?1?Cellulose nanopaper for application in light management.A superhydrophobic?static contact angle=159.6°,sliding angle=5.8°?,highly transparent?90.2%?and hazy?46.5%?nanopaper made of TEMPO-oxidized cellulose nanofibrils?TOCNF?and polysiloxanes was fabricated by vacuum-assist filtration and silanization.The constructed pearl-necklace-like polysiloxanes fibers on the nanopaper surface significantly improved water repellency?70.7%for static contact angle?and toughness?118.7%?of the TOCNF nanopaper.The proposed novel nanopaper that simultaneously achieved light-management and self-cleaning capabilities,not only led to an enhancement?10.43%?in the overall energy conversion efficiency of the solar cell,but also addressed the solar cell's problem of work efficiency decline due to dust accumulation.?2?Crepe cellulose paper-based flexible anisotropic strain sensor.The commercially available crepe paper made of the abundant and renewable cellulose is converted into a conductive network by carbonization.The as-fabricated strain sensor based on this carbonized crepe paper?CCP?and PDMS exhibits high flexibility,fast response time?<115ms?,high durability?>10 000 cycles?,and negligible hysteresis.Especially,the CCP strain sensor shows dramatically different gauge factors?10.10 and 0.14,respectively?between tensile bending perpendicular and parallel to the fibers'direction.This anisotropic sensing performance is inherited from the crepe paper's unique anisotropic structure,i.e.,aligned cellulose fibers and a corrugated surface,which is well maintained in the CCP.In addition,the CCP strain sensor's practical use in detecting complex human motions and controlling a2?degree?of?freedom machine is demonstrated,indicating their potential applications in multidimensional wearable electronics and smart robots.?3?Cellulose paper-based highly sensitivity and flexible pressure sensor.The screen-printed interdigital electrodes on the flat printing paper and the carbonized crepe paper?CCP?with good conductivity are integrated to fabricate a flexible pressure sensor as the substrate and active material,respectively.The porous and corrugated structure of the CCP endows the pressure sensor with high sensitivity(2.56-5.67 k Pa^-1 in the range of 0-2.53 k Pa),wide workable pressure range?0-20 k Pa?,fast response time?<30 ms?,low detection limit??0.9Pa?,and good durability?>3000 cycles?.Additionally,the practical applications?detection of wrist pulse,respiration,phonation,and acoustic vibration,as well as real-time monitoring of spatial-pressure distribution changes?of the CCP pressure sensor were demonstrated.This indicated the sensor's practical application value in the fields of health care,motion detection,and electronic skin,etc.?4?Paper pressure sensor based on composite cellulose aerogel.A conductive composite carbon aerogel,made of nanocellulose?TOCNF?and carbonized bacterial cellulose?CBC?,with hierarchical microstructure was prepared by a directional freezing template method.This aerogel was used as the active material to prepare a novel paper-based pressure sensor.TOCNF significantly promoted the crushing effect of ultrasonic treatment on CBC and improved the dispersibility of CBC fragments in water.A variety of composite carbon aerogels with different micro-morphologies were prepared.The sensitivity of the sensor under different pressure load ranges was adjustable.The paper-based pressure sensor also has a wide working range?0-100 KPa?,fast response time?<110 ms?,slight hysteresis,and signal reliability.The sensors as wearable devices could be applied in motion detection,touch monitoring,and footstep sensing.Furthermore,the mobile interconnection between the sensor and smartphone was achieved via Bluetooth.?5?Paper-based triboelectric nanogenerator?P-TENG?for application in energy harvesting and self-powered pressure sensing.Folded print paper is used as the substrate,while crepe cellulose paper?CP?paired with a nitrocellulose membrane?NCM?are used as the friction layers of the P-TENG.CP and NCM have significantly different tribo-polarities and microstructures?i.e.,corrugated and porous structures for CP and NCM,respectively?,thereby yielding P-TENGs with outstanding triboelectric performance.The P-TENG has an output voltage of 196.8 V,an output current of 31.5?A,a high power density of 16.1 W/m²,and a robust durability of more than 10000 cycles.The as-fabricated P-TENG successfully drove a variety of electronic devices through mechanical energy harvesting,and simultaneously achieved the applications in the field of self-powered pressure sensing and self-powered human-machine interaction.