Modeling And Analysis On The Process Of Inserting Microneedle Into Skin

The microneedle-based drug delivery technology is a new transdermal drug delivery technology that provides continuous,painless,minimally invasive,timed,and quantitative drug delivery.The interaction between microneedles and living skin tissue is one of the focuses of research on microneedle drug delivery technology.Only by fully understanding the interaction between skin and microneedles can we design a durable microneedle structure that does not break down during use,and achieve stable transdermal administration.However,skin tissue is a relatively complex structure of the tissue,and the mechanism of influence on skin tissue cannot be ignored.In this paper,the mechanical mechanism of the skin is first studied,and the mathematical model is established by simplifying the skin structure,which provides the theoretical basis for the stress analysis on the process of micro-acupuncture into the skin.Secondly,based on the modeling on microneedle structure,it is concluded that the microneedle is subjected to friction resistance,bending force,axial pressure,shear force and so on during the process of stabbing into the skin.Furthermore,the contact model between microneedle and skin is put forward and analyzed.Based on the analysis of the interaction mechanism between the microneedle and the skin,the microneedle structure and its biomechanical interaction with the skin tissue are analyzed and discussed.As an example,our structure of microneedle tip is modeled and simulated,including the effect of microneedle structure on the length,the thickness,the needle wall angle and other factors on the skin.Combined with the finite element analysis method,the contact simulation analysis is carried out during the process of micro-acupuncture into the skin,the interaction mechanism and mechanical response of microacupuncture into the skin are studied.The results show that the puncture force of the microneedle decreases linearly with the decrease of the end area of the tip of the microneedle.With the increase of the diameter of the microneedle,the fracture force of the microneedle increases gradually.The puncture force of micro acupuncture into the skin tends to flatten when the angle of the needle is greater than 70 degrees.Taking into account the above factors,our hollow microneedle with ultra-sharp star and side openings has good puncture characteristics and small puncture force required.The structure can potentially eliminate the skin tissue blocking,and can effectively improve the delivery rate of the drug.In addition,the characteristics of the microneedle are simulated and compared with the previous microneedles.The characteristics of three kinds of microneedles,such as solid tip,needle tip with top tip-hole and tip with solid tip and side openings,are compared and analyzed,which show that our microneedle structure has the advantages of good puncture characteristics,preventing unnecessary loss of liquid and blocking and high liquid conveying efficiency.Finally,the process flow of our microneedle array is designed,and the key processes are analyzed and discussed in detail.