Fabrication Of Multi-layer Microfluidic Chip And Primary Multifunction Integration In The Biomimic Chip

Animal silks have been a focus of research for their excellent mechanical properties and high efficiency,environmentally friendly spinning process.The main methods to fabricate the regenerated animal silks are wet spinning,dry spinning or electrospinning,which are difficult to adjust the polymer composition and structure during the spinning.With the development of microfluidic technology,researchers have found that spinning apparatus of animal at micron scale can be regarded as a microfluidic device.This provides a new route to improve the biomimic degree.In this paper,we designed a 3-dimensional complex micro fluidic chip which integrated the functions of dynamic adjustment,concentration,shearing and elongation,based on the functions and structure of the spinning apparatus of spider and silkworm.The chip was prepared using the technologies of photolithography and rapid prototyping.In this process,we used glass slide as substrate,regenerated cellulose membrane as semipermeable membrane,SU-8 as material of mold,and polydimethylsiloxane(PDMS)as material of chip construction,respectively.In order to bond regenerated cellulose membrane and PDMS,we studied the effect of bonding by different adhesives,including epoxy adhesive,silicone adhesive and pressure-sensitive adhesive.Results showed that the multifunctional microfluidic chip was bonded effectively under the condition of plasma pretreatment with epoxy adhesive.The PDMS-PDMS surfaces and PDMS-cellulose membrane surfaces could be bonded firmly by using silicon adhesive(E41)and pressure-sensitive adhesive,respectively.Adjustment media,mixture of polyethylene glycol(PEG)and calcium chloride(CaCl2)aqueous solution,was injected into the bottom channel of chip to study the composition adjustment effect of regenerated silk fibroin(RSF).Results showed that the concentrations of RSF and Ca2+ in the RSF solution flowed from outlet were enriched obviously.The adjustment of concentration and Ca2+ were increased with the decrease of flow rate of RSF,and concentration of RSF solution.In the case of the high flow rate of adjustment media,the adjustment effect increased first and then decreased.It's necessary to find a optimized flow rate and initial concentration of RSF solution to obtain a spinning dope.The time-consuming and high-cost limited the fabrication of microfluidic chip.Therefore,computer simulation techniques were applied in this study to build mathematical model of the adjustment of RSF composition in microchannel of chip.Compared the simulated results with our experiment data,we found that simulated results matched well with experiment data.This demonstrated that our model was reasonable to simulate the adjusting process of RSF solution in chip.Based on the above adjustment results,we investigated the integrated spinning function of the multifunctional microfluidic chip.In this process,the solution with 40 wt%RSF and 0.2 mol/L Ca2+ was used as spinning dope.The as-spun silk fibers were drawn and immersed in ethanol(80 vol%)to improve their mechanical properties.The posttreated fiber exhibit a initial modulus of 6.8 GPa,a breaking strength of 142 MPa,and a breaking strain of 18%.Although the fiber was still weaker than natural silkworm silk,we first integrated multiple functions of the natural spinning apparatus.These functions include protein composition adjustment,shearing and elongation of spinning dope and spinning.The integration may have significant influence on the application of microfluidic technology in bio-inspired spinning.