Electrospun Nanofibrous Membrane Constructed Triboelectric Nanogenerator For Human Mechanical Energy Harvesting

In recent years,with the advent of a series of products such as Mi band,Google glasses and Nike smart sneakers,people have shown a strong interest in wearable electronic devices.Furthermore,with the rapid advancement of modern technology,an increasing number of functional devices based on micro/nano techniques are widely applied in the wearable field.Although the energy consumption of micro electronic devices is relatively few,the miniaturization and wearable requirements of electronic devices largely limit the volume of energy-supply units.For traditional batteries,the small size indicates that their storage capacities are limited,which seriously shortens the working time of wearable electronic devices.Therefore,it is an urgent problem for microelectronics industry and wearable technology to provide continuous and stable energy for these micro devices.Reliance on the coupling effects of contact electrification and electrostatic induction,triboelectric nanogenerator(TENG)has been proven to be a fundamentally new green energy technology for ambient mechanical energy harvesting,which is one of the effective ways to address the sustainable green energy supply for wearable electronic products.In order to improve the electric output performance,the triboelectric materials used always need to be functionalized by photoetching,plasma etching or electrochemical corrosion to generate special nanostructure surface.However,such commonly used techniques are largely shadowed by limitations such as expensive equipment and complex process.Alternatively,electrospinning is an effective method for the preparation of micro-nano fibers.It exhibits the compelling advantages of simple equipment,low cost and continuous production.Electrospun nanofibers have the merits of small diameter,high specific surface area and various fiber morphologies.The TENG constructed by such electrospun nanofibrous membranes performs a higher performance when compared with the smooth films.In this paper,we presented TENGs with nanofibrous membrane as the core working part of the devices.Besides,the electrospun nanofibrous membranes were effectively tailored to enhance the triboelectric polarity,mechanical strength and humidity-resisting property by advanced material design approaches,which greatly boosted the device’s output performance and resistance to high humidity condition around human body after perspiration.The electrospun triboelectric nanogenerator was designed to form self-powered electronic devices through a reasonable circuit design.Moreover,it was integrated with dailylife clothing to form electric generating devices for human mechanical energy harvesting.The specific research results were divided into the following two aspects:(1)The blended nanofibrous membranes with good mechanical strength were prepared by tailoring the blending ratios of cellulose acetate(CA)and polyurethane(PU).Subsequently,the CA/PU blended nanofibrous membrane was modified by polyacrylamide(PAM)and it was designed to form a surface amino modified TENG(AM-TENG).The obtained output charge,opencircuit voltage and short-circuit current of AM-TENG increased by 60%,83% and 91% respectively and such measured values maintained high electric performance under even high humidity conditions.Self-powered thermometers,self-powered watches and self-powered calculators could be built through using the AM-TENG as the core part and a reasonable circuit design.These selfpowered electronics could work normally by harvesting human body mechanical energy,which showing great application potential in the field of wearable electronics.(2)The polyvinylidene fluoride(PVDF)and polyacrylonitrile(PAN)nanofibrous membranes with small fiber diameter and continuous uniformity were obtained by controlling the polymer concentration.Subsequently,PVDF nanofibrous membrane was coated by PDMS and etched by alkali to produce composite nanofibrous membrane with strong electronegativity.Similarly,PAN nanofibrous membrane was coated by Polyamide 6(PA6),etched by acid and grated by long-chain alkane to obtain composite nanofibrous membrane with strong electropositivity.Two composite nanofibrous membranes were designed to form nanofibrous membrane TENG(NM-TENG),which could retain excellent electric performance under high humidity conditions,work 6000 times continuously and its instantaneous energy density could reach as high as 14.8W/m2.Electric generating devices were successfully constructed by combining NM-TENG with fabrics and insoles,which could power 10 LEDs and 400 LEDs respectively.