Beyond needles: redefining drug delivery via confining high-velocity jets with viscoplastic fluids

Humboldt Research Fellowship Programme for Experienced Researchers
While needles and syringes are among the common methods to administer vaccines and dermatological medications, they suffer from numerous disadvantages, including unsafe practices, exposure to infections, needle phobia, lack of reusability, and disposal and environmental problems. A safe alternative to deliver vaccines and other immunological products is the needle-free injection method (NFIM), using a high-velocity liquid jet created via a laser pulse exciting the injection drug fluid. Major limitations of this method are severe pain, penetration depth variability, skin hole size variability, skin irritation, etc. Many of these limitations have roots in the jet flow dynamics and they are caused by undesirable jet dispersion, jet widening, jet flow instabilities (e.g. droplet formation), atomization or spray, jet tip deformation, splash, inhomogeneous penetration into skin, etc. In this context, my interdisciplinary research project proposes to remove the aforementioned limitations of the NFIMs, via immersing the high-velocity liquid jet into a viscoplastic fluid, filling the space between the liquid drug and the skin (known as the stand-off). This high-risk approach may allow us to use a viscoplastic fluid to properly surround the jet, confining it to a stable cylindrical form that precisely/controllably penetrates into the skin target area, while reducing the jet widening and jet instabilities (break-ups); subsequently, the jet can reach the desired penetration depth, with a precise penetration width/shape. My specific research objectives include: (i) examining the effects of filling the stand-off distance with viscoplastic fluids on the jet flow development, possibly stabilizing and controlling the jet; (ii) examining the subsequent penetration of the submerged jet into a multilayer skin model; (iii) analyzing the skin model response to the jet penetration. These objectives will be achieved via novel experiments and mathematical modeling approaches.