Mechanical and fluidic analysis of hollow side-open and outer-grooved design of microneedles

This paper presents a novel concept design for microneedles that can perform dual release patterns by utilizing outer grooves as a pathway for instant delivery, dissolving body microneedles which are loaded with stimuli-responsive nanocarriers for sustained delivery and a bore for extraction diagnosis purposes. ANSYS software is used to analyze the performance of the proposed design involving mechanical structural and mechanical-fluid dynamics analysis. The effect of various grooved designs on skin puncture performance on the tri-layer skin model has been investigated, and the presence of grooves can minimize contact interaction, leading to low insertion force. Then, instant delivery via the outer grooves, which involves open-channel and closed-channel, is studied (0.033 mu l/min). For dissolution performance for limited and sustained source loading is investigated using analytical analysis. With a set extraction flow rate of about 0.0015 mu l/min and a vacuum pressure of 10kPa, the bore design is optimized to minimize vortex formation. Lastly, the structural strength of the proposed microneedle is investigated by applying axial and transverse loads which show the generated stress is less than the material strength. Overall, simulation results confirm that the proposed microneedles can provide both sustained-instant release of insulin simultaneously and perform extraction with minimal vortex formation to provide precise sampling amount and avoid delay of fluid movement. This design has high potential to be used in developing a closed-loop system for transdermal insulin delivery and diagnosis, known as "artificial pancreas".