Numerical Simulation, Analysis, and Fabrication of MEMS-Based Solid Ag and Cu Microneedles for Biomedical Applications

Abstract

Microelectromechanical system (MEMS)-based devices have gained attention recently due to their beneficial biomedical applications. MEMS-based devices like microneedles have set new trends in drug delivery, vaccination, skin, and eye treatment. Different materials like metals, sugars, polymers, and silicon have been used for fabrication. Various techniques have been used for their fabrication, including laser ablation, lithography, injection molding, and additive manufacturing. The tip diameter of different micron ranges has been achieved. The strength and stiffness of the microneedle’s tip have always been important in fabricating microneedles so that it does not break on insertion. This research paper presents a comparison between silver (Ag) and copper (Cu) solid microneedles by performing numerical analysis using the fuzzy approach, structural simulation, and fabrication. Firstly, structural simulation has been performed in ANSYS software to test the strength of silver (Ag) and copper (Cu) microneedles separately. The purpose is to compare the stress effect and fracture limit of both microneedles. The results collected from the simulation provide valuable target and prediction facts to fabricate improved designs of the solid Ag and Cu microneedles. Then, fuzzy-based numerical analysis has been performed in MATLAB software for both microneedles separately. In this numerical analysis, the effect on the range of microneedle tip diameter and cone length has been observed by varying input voltage and time. Finally, fabrication has been performed using a novel economical technique such as electrochemical etching. Electrochemical etching is a very low-cost and clean room-free technique as compared to other techniques used for the fabrication of microneedles. The fabrication technique adopted in this work is the same for both silver and copper microneedles. The scanning electron microscopy (SEM) characterization has been performed for both fabricated microneedle tips. The tip of the fabricated solid Ag and Cu microneedle has been then coated with drugs using the dip-coating method. The coated solid Ag and Cu microneedle’s tip has been then characterized again using SEM. The numerical results calculated from the fuzzy analysis have been then compared with fabrication results. The fuzzy analysis gives the simulated size of the microneedle’s tip for 5.05 μm silver and 5.12 μm copper which have very close approximation with the experimental values from the SEM micrographs which also give the values of the cone length from 400 to 500 μm and the tip size from 5 to 6 μm for the time of 10–15 minutes, whose values were optimized by the fuzzy analysis. The results of this research provide valuable benchmark and prediction data to fabricate improved designs of the silver solid microneedles for drug delivery and other biomedical applications.