The Reseach Of Mems-based Metal Microneedles For Micro Injection/Sampling

Microneedles have been drawing great attention since it was born in 1970 s due to the ability of transdermal injection by minimal-invasive and pain-free manner.However,most of the research on microneedles is still in academic stage without obvious breakthroughs in the practical application in recent years.Therefore,exploration of new type of microneedles and its fabrication technologies to promote the application of microneedles is the untiring pursuit of academia and industry.Microneedles refer to the needle of length from hundreds microns to several millimeters and owning a shaft with diameter from several microns to hundred microns as well.There are two kinds of microneedles: solid and hollow.Hollow microneedles have a flow channel in the core comparing with solid microneedles.On the other hand,microneedles are usually made by silicon,polymer,metal,glass and so on.In additional,from the fabrication precesses of microneedles,it can be divided into two principal groups called in-plane and out-of-plane based on their general design.In-plane microneedles have shafts that are parallel to the substrate plane which limits the length of microneedles.However,out-of-plane microneedles have shafts perpendicular to substrate making it much easier to adjust the microneedle structure and size.The ability of realizing minimally invasive,painless micro injection/sampler is one of the most important reasons for microneedles research.Therefore,reducing the size of microneedle which owns a length long enough to overcome the skin viscoelasticity as well as good intensity and a base which contributes to assemble microneedles with other components is the ultimate pursuit.Given the various requests above,the traditional process technology can’t overcome the challenge of reducing microneedle size and highly integrated non silicon micro-nano manufacturing technology provides the advantage of technology to achieve that goal.Highly integrated non silicon micro-nano manufacturing technology based on the principle of superposition of microstructure thin film to build complex microstructure system is match with the requirements of size,microstructure and materials.So,highly integrated non silicon micro-nano manufacturing technology is feasible and reasonable for the process of micro sampling/injection microneedls.Based on the background above,this paper has focused on the research of MEMS-based metal microneedles for micro injection/sampling and its application in biomedical field.In this paper,the main research content and the progress is as follows:(1)The design of in-plane hollow metal microneedles has been finished on the basis of combining theoretical analysis and numerical simulation as well as preparation and application of comprehensive analysis.At the same time,microneedle array for large doses requirement have also been designed based on the research results of similar microneedles before.(2)This research introduced reshaped photoresist technology to form arc structure for microneedle channel by baking sacrificial photoresist in the fabrication process for rapid scale-up,inexpensive and mass production of ultrahigh-aspect-ratio hollow metal microneedles.Through a series of actual microneedle fabrication experiment,the process has been optimized gradually to tend to be more stable and mature by realizing the process of other hollow metal microneedles with different characteristics.The whole fabrication process owning the stability,compatibility for more microneedles may provide technical reference for overcoming the problem of microneedles process by traditional needles technology.(3)Based on the microneedles researched in this study,a micro sampler and an injection connector have been designed and fabricated.The actuator chamber of micro sampler has been optimized to decrease dead volume by simulation software ANSYS which simulated the deformation rule of different chambers under stress load.With a more precise volume for smpling,the possibility of sampler to be used in actual has increased a lot.Besides,the exploration on microneedle application system by casting polymer has been a foundation for other research in futures.(4)The performance of microneedles and its application systems have been tested by different experimental instruments and test methods.The ability to bear the axial force and bending force of different single microneedles has been tested by binding force tester.And data of inserting force of different skins of microneedles has been collected by adjusting the test method as well.All of the mechanical test results before have played a great role to evaluating the security of microneedles researched in this study.The flow rate value of microneedles has been successfully collected by referring the test method of traditional needles.The micro sampler and injection connector has been tested by different test schemes based on other research results of microneedles application systems.And the whole test has verified the design idea of mironeedles micro systems,laying a foundation for the subsequent research for us.