Research On 3D Printing Technique Of Sacrificial Structure Of Microfluidic Chips With Adjustable Cross-section

Microfluidics has a wide range of applications in the fields of chemistry,biology,and medicine,and it has developed into a multidisciplinary research area of fluids,machinery,electronics,biology,chemistry,medicine,and materials.Microfluidic chips as the carrier of microfluidics,its requirements on manufacturing materials and internal channel structure pose the manufacturing process a lot of difficulties.Although the traditional processing technology represented by soft lithography can realize the mass production of microfluidic chips,from the aspects of channel structure,chip material,cost,etc.,the traditional process has great limitations.The rise of 3D printing is expected to solve these problems.3D printing features strong designability and high automation,which just fits the needs of microfluidic chips with small batch,low cost,and fast fabrication.It is expected to become a new manufacturing method of microfluidic chips.Considering that traditional microfluidic chips are mainly manufactured by classic micromachining methods,the cross section of the channel is almost rectangular,trapezoidal and circular.The single shape of the cross section of the channel makes the flowable and controllable design of the chip lack many dimensions.And it also makes the channel and chip limited in two-dimensional form.Can we use 3D printing technology to realize the profiled flow channel cross section and even control the flow channel cross section to achieve the flow controllability of the chip? Our research group proposed a manufacturing method of microfluidic chips utilizing embedded sacrificial elements in 2015.The microfluidic chips were achieved by using soluble sugar as the sacrificial material printed by the printer,and then immersed the microfluidic chips in water to solute the sacrificial material after printing.Based on this research,in order to give the structural design of the flow channel in the microfluidic chips higher designability and freedom,the concept of microfluidic chips with an adjustable cross section is proposed.And the printing process is improved to achieve 3D printing of microfluidic chips with an adjustable cross section using PDMS and Gel MA hydrogel materials.The specific work of this thesis is as follows:1.We have studied the microfluidic chips' manufacturing process based on the embedded sacrificial elements.Firstly,we modified the 3D printers based on the microfluidic chip manufacturing method with the embedded sacrificial elements.Then,the system explored the effects of nozzle temperature,extrusion pressure,and printing speed on the diameter of the sugar filament,and achieved a stable and accurate manufacturing of the specified diameter of the sugar filament.Then,the optimized printing process of the bifurcated structure commonly existing in the micro-channel structure is proposed,and its manufacturing stability is verified.These have laid a solid foundation for subsequent process research.2.The concept of microfluidic chips with adjustable cross section and their printing process are proposed.Firstly,the element of 3D printing is analyzed,and a microfluidic chip scheme with adjustable cross-section is proposed.Then,after improving the printing process,an example of PDMS microfluidic chips with an adjustable cross-section and a complex structure was fabricated.Finally,a simple cell culture was performed using PDMS microfluidic chips with a bifurcated structure and an adjustable cross-section internal channel to simulate the thrombus structure in blood vessels,which verifies biocompatibility,and demonstrates potential applications.3.The manufacturing process of microfluidic chips with adjustable cross-section based on hydrogel material was further proposed.Firstly,a process of adding a polymer coating on the surface of sugar was proposed,which solved the main problem of sugar filaments dissolving too quickly in the hydrogel and causing large deformation.In addition,in order to solve the problem of low strength of the hydrogel twice-cured joint surface,a manufacturing process of integral molding is also studied.And then we analyzed the manufacturing stability according to the newly proposed process method and the unique swelling characteristics of the hydrogel.4.An osteogenic organ chip was produced.Human endothelial cells and bone mesenchymal stem cells were used for three-dimensional culture.The analysis of the state of live / dead,skeleton,migration,etc.,fully demonstrated the biocompatibility of gel-based microfluidic chips and their broader biomedical application prospects than PDMS chips.