Preparation Of Polydimethylsiloxane Fibers And Their Applications As Flexible Optics And Electronics

With the significant advancement of materials science and technology,flexible optics and electronics,wearable devices,bionic engineering,biomedicine and other fields,flexible functional materials with electrical conductivity or photoconductivity have become a significant trend in the development of flexible and wearable materials in the future.Functional polymeric fibers have attracted considerable attention in wearable applications due to their excellent deformability,including bendability,stretchability,and twistability.They are expected to be one of the alternative materials in flexible optics and electronics.However,existing systems still face challenges in preparing fibers from some polymers exhibiting a slow crosslinking rate,such as difficulty in mass and controllable production of continuous fibers,limiting their applications in flexible electronics and optic.This thesis focuses on the core problem in preparing polydimethylsiloxane（PDMS）fibers,to explore a fabrication method to process PDMS and some other polymers exhibiting slow cross-linking rate into fibers,and further investigate their functionalities and application areas.Using Sylgard184 PDMS and SE1700 PDMS as the primary research objects,flexible fibers with ultra-long length,controllable morphological dimensions and excellent mechanical properties were prepared by a microfluidic spinning technology based on coaxial needles.The influences of injection rate and conductive additives on fiber properties and their optical properties,are revealed,and the applications of these fibers for serving as resistive optical strain sensors targeting mechanical signals are also systematically investigated.The main contents of the paper are as follows.A coaxial needle-based microfluidic method was developed for spinning the fibers with these slow-curing polymers as the inner core,and sodium alginate hydrogel as the protective shell.This method enables the fabrication of fibers with controlled morphology and ultra-long length.The method was applied to Sylgard184 PDMS and SE1700 PDMS.The feasibility of the microfluidic coaxial spinning method was verified by controlling the flow rate of both the inner and outer solutions to produce uniform,ultra-long,and flexible fibers with controlled morphology.In addition,the broad applicability of this method was verified by the preparation of fibers from other polymers（Ecoflex,one-component glass glue,two-component polyurethane,and one-component polyurethane）.Carbon nanotube（CNT）/PDMS conductive fibers with ultra-long length,high stretchability（135%）,and conductivity were obtained by this coaxial needle-based microfluidic spinning method by mixing Sylgard184 PDMS with CNT.The factors affecting the performance of CNT/PDMS conductive fibers were investigated to tune the size and performance of CNT/PDMS fibers.The flexible mechanical sensor constructed with CNT/PDMS conductive fibers has a sensitivity of GF=2.009,a response time of 0.27 s,and a high durability（over 10,000 stretching cycles）,which can be applied to monitor joint movements and swallowing behavior.Based on the microfluidic coaxial spinning method,different sizes of Sylgard184 PDMS fibers were prepared and obtained,which have high light transmission,photoconductivity,and high tensile properties（195%）.The factors affecting the performance of PDMS optical fibers were investigated to tune the size and performance of PDMS optical fibers.The optical strain sensor constructed with PDMS fibers has high sensitivity,a fast response time（160ms）,high stability and durability（>10,000 stretching cycles）.It can monitor mechanical signals such as tactile pressures,and even pulse beats.