Optimizing Transdermal Insulin Delivery: A Simulation Study on the Efficacy of Sonophoretic Transducer Arrays at Low Voltages

Insulin therapy is integral to the treatment of diabetes mellitus. Epidemiologic studies have shown its benefits both in terms of improving glycemic control and reducing the risk for long-term diabetic complications for both type 1 and type 2 diabetes. Despite these benefits, barriers to insulin therapy are well documented and include perceived inconvenience, needle anxiety, and portability of device in case of insulin pumps. Therefore, this study aims to design and simulate a low frequency sonophoretic array for transdermal insulin delivery. This study utilizes COMSOL Multiphysics software to simulate the transducer used to increase the skin permeability for delivering drugs. It consists of $8\times 5$ array of a piezoelectric elements operated at 100 kHz and 1 volt. To evaluate the effectiveness of the transducer, an intricate skin model has been developed that includes all anatomical layers extending to the bone. The skin layers, particularly muscle and bone, exhibit reflective properties, leading to the formation of a standing wave. This phenomenon arises from the impedance mismatch between muscle and bone. Standing wave served to promote the transportation of the drug into the dermal layer, rich with capillary networks. We found that applying standing wave with 100 kHz the achieved pressure of 0.3 MPa induced acoustic streaming for the drug flow of $1605~\frac {\mathrm {\mu g}}{{\mathrm {cm}}^{2}}$ per 24 hours. Also, the precise modulation of ultrasound frequency and voltage is key to controlling peak acoustic pressure, thereby regulating the rate of insulin delivery through the skin.