Microparticle Formation via Tri-needle Coaxial Electrospray at Stable Jetting Modes

Multilayered structured organic particles have had an extensive impact on a wide array of biomedical applications not limited to drug delivery, imaging, and biosensing. A tri-needle coaxial electrospraying system was utilized to engineer multilayered polymeric particles in a one-step, facile process at ambient temperatures. The effect of the dominant processing parameters on the development of a conical cusp that eventually ejects an ultrathin liquid ligament was first explored here. Subsequently, the validation of the intermediate solutions that possessed different conductivities on stabilizing jetting modes and the resulting particle morphology was also investigated. Polycaprolactone (PCL) solutions with different molecular weights were selected as the outer layer using fluids with various conductivities. Five different formulations were studied as the intermediate layers: PCL in acetic acid, ethyl cellulose in acetic acid, ethyl cellulose in dichloromethane, ethyl cellulose in ethanol, and silicone oil and polyvinyl pyrrolidone in water. The results systematically demonstrated that the processing parameters (type of polymer, polymer molecular weight, solution concentration, flow rate, applied voltage, and collector distance) play a significant role in the formation of the stable Taylor cone. This study further identified that the coaxial arrangement of three needles successfully produced multilayered microspheres with uniform size distribution.