| In the case of the form of fibers, electrospinning is one of the ideal technologies for preparingtissue engineering scaffolds as electrospun scaffolds mats closely mimic extracellular matrix. Thistraditional spinning technique, while overly simplistic, is not possible to reproduce the dynamiccharacter and the complexity of the in vivio process by which natural fibers are formed. Thespinning ducts of spiders or silkworms can be considered as typical microfluidic devices.Microfluidic technology can be used to control, operate and test complex fluids, even spin fiberson micrometer scale. In this paper, we combined microfluidic technology and electrospinningtechnology, microfluidic chip and PEEK have been applied as spinning devices to electrospinfibrous mats from regenerated silk fibroin (SF) aqueous solution. The electrospinning spinnabilityand optimum spinning parameters were investigated. The microfluidic chips with differentdimensions of spinning apparatus were also designed and adopted to study the effect of elongationand shearing condition on the structure transition of SF mats. Finally, the new composite materials,SF/silk sericin (SS), SS/SF/SS mats were fabricated successfully. Scanning electron microscopy(SEM), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray diffraction,differential scanning calorimetry (DSC), material testing machine and capillary flow porometerwere employed to investigate the morphology, structure, properties of the SF mats.The effects of electrospinning parameters on the diameter, structure and property of the fiberswere studied. Results showed that optimal parameters were as follows: the mass fraction of SFaqueous solution was33%, the voltage applied was25kV and the flow rate was1.2mL/h. Wechanged the dimensions of the spinning apparatus (various widths of outlet channel, elongationlengths and shearing lengths). We found the increasing shear time and elongation rate couldpromote conformation transition of SF fibers.The morphology and property of the fibers electrospun by PEEK were also influenced byprocessing parameters including inner diameter of PEEK, mass fraction of SF solution, voltageand flow rate. Fibers with uniform cylindrical structure and smooth surface were obtained at amass fraction of33%, a voltage of25kV and a flow rate of1.2mL/h. Compared with thetraditional stainless steel nozzles and PEEK for electrospinning, the microfluidic chip as aspinneret can produce the mats with finer fibers and smaller pores. Microfluidic chip could alsopromote conformation transition of SF fiber and increase the content of β-sheet, crystallinity andmechanical property in some extent.In this thesis, spinnability of regenerated SF and SS aqueous solutions was also investigated.The SF/SS mat has been successfully electrospun by using microfluidic chip with two inlet channels. Due to the laminar flow characteristic of microfluidics, the SF solution and SS solutiontended to keep their laminar streams without mixing. Besides, the two fluids were spunrespectively without mixing and the mats had a smooth surface. From the SEM images, two formsof fibers with different degrees of thickness could be observed clearly. In the case of PEEK, the SFsolution and SS solution also were spun respectively, but the SS fibers tended to break up easilyand the mats had a poor surface.The SS/SF/SS mats had been fabricated by using microfluidic chip with three inlet channels.The SS solution and SF solution flowed from outer and inner passage respectively. It wasobserved that SF fiber and SS fiber twist together to form a unique sandwich structure. Thelaminar flow characteristic and controlled diffusion made it possible to realize complicatedmanipulation of the fluid by using the simple microfluidics design. We expect to use the novel andflexible microfluidic electrospinning technology to fabricate multifunctional, complicated,predictable and controllable silk fibrous nanofibers. It has great potential in biological release,gene modification, medical test area. |
PDF Full Text Request