Preparation And Triboelectric Property Of PDMS Based Flexible And Transparent Composite Materials

As a new energy collection technology,triboelectric nanogenerator(TENG)can convert mechanical energy generated in the environment or human body into electrical energy.It is an ideal energy supply device for wearable devices.The research on TENG has received extensive attention,but its output performance is still far from the practical application.In addition,it should also pay attention to its flexible and transparent characteristics of TENG due to the applications such as wearable devices and electronic skin.This study has designed a variety of methods to modify PDMS to improve triboelectric performance and keep the flexible,transparent characters of TENG:The physical incorporation of polytetrafluoroethylene(PTFE)into PDMS shows that PTFE exists in PDMS with the form of particles.The output voltage and transfer charge of PDMS/0.1PTFE based TENG with the best match were 90 V and 90 n C,respectively,which are more than three times of the output performance of pure PDMS/based TENG devices.The work function of the PDMS material is changed,and the surface potential is increased after the incorporation of PTFE material,which changed the distribution of electric charge in the friction process.The output performance of the TENG improved with more electric charge distributed in PDMS/PTFE material.The PDMS/PTFE based TENG can light up to 104 blue commercial LEDs and charge commercial capacitors to drive small electronic devices.Meanwhile,the prepared device maintains good transparency(72.7%)and flexibility.PDMS materials were modified by perfluorododecyl trichlorosilane(FDTS)and PDMS/FDTS films with different doping amounts were obtained.Copper nanowires(Cu NWs)and reduced graphene oxide(r GO)composite was prepared by one-pot method and fabricated into transparent flexible electrodes to further improve the transparency of the TENG device.The highest output performance was achieved at the doping amount of 2 wt%,with the output voltage and transfer charge of 125 V and 90 n C,respectively,which are five times and three times of the output performance of pure PDMS based TENG.The improvement of performance of TENG is attributed to the change of surface potential distribution and capacitor of modified materials which affectes the distribution of charge during friction,and finally makes more charge distributed in the PDMS/FDTS material.The PDMS/0.02 FDTS based TENG can light up 160 small blue commercial LEDs directly,and charge commercial capacitors to drive electronic devices.The prepared device demonstrates flexibility and better transparency compared to the commercially assembled electrode device.Finally,fluorination modification and surface structure construction were used to prepare the modified PDMS films.TENG based on the modified PDMS film shows a output voltage of 350 V.Copper nanowires(Cu NWs)with more than 2000 of length-diameter ratio were prepared by hydrothermal method and were used to fabricate semi-embedded structure electrode with stable and durable performance while keeping transparent and flexible.PDMS/Cu NWs friction layer materials were prepared by mixing different amounts of Cu NWs into PDMS materials.The corresponding analysis and measurement were carried out for the synthesized materials and PDMS/Cu NWS based TENG respectively.Using PDMS/Cu NWs thin film as negative friction layer material and fabricating semi-embedded copper nanowires electrode,contactseparate mode TENG devices and single-electrode mode TENG devices were assembled respectively.When the doping amount was 0.9 mg,the output performance and transparency performance reached optimum matching.The output voltage and transfer charge are 105 V and 70 n C,which are 4 and 2.5 times of the output performance of pure PDMS based TENG devices,respectively.The doping of Cu NWs will affect the microcapacitance structure of the friction layer material and increase its ability to store charges so that the performance is improved.At the same time,the copper nanowires distributed on the surface will store more charge in the friction layer,which will also increase the output performance of TENG.The PDMS/0.9Cu NWs based contact-separation TENG can be used for signal display,and it can charge commercial capacitors and supply energy for different devices to make them work normally after being assembled with the designed circuit.The PDMS/0.9Cu NWs based single-electrode TENG shows good transparency(82.3%)and flexibility,and can be attached to a mouse to detect mouse operation or attached to human body as a force sensor to respond to the contact between the skin and the outside world.The solar energy/friction energy hybrid energy collecting device can collect the friction energy of solar energy and water droplets.In order to improve the air permeability of the film-based TENG,this study designed a chemically modified PDMS/FDTS to dip nanofibers to prepare composite materials to achieve both transparency and air permeability of the material and the device.The polyvinyl alcohol(PVA)nanofibers were prepared by electrostatic spinning method,and the influence of preparation parameters on the nanofibers was investigated to obtain the nanofibers suitable for dipping.By dipping the nanofibers with different concentrations of PDMS solutions,the friction layer materials with transparent and air permeable were prepared.To further improve the output performance,diluted PDMS/FDTS solution was used to dip the nanofibers.Meanwhile the transparency,air permeability and excellent hydrophobic properties(126.6°)of the dipped samples were demonstrated and the PDMS/FDTS dipped nanofibers based TENG was attached to human body to detect human motion.