Numerical simulation of heat transfer from a transonic jet impinging on skin for needle-free powdered drug and vaccine delivery

Abstract

In this paper, gas dynamics and temperature distribution of a transient impinging jet, typically used to deliver powdered drug or vaccines ballistically to the skin, have been numerically simulated. Calculations were performed with the unsteady compressible Navier-Stokes equations, solved using a modified implicit flux vector splitting (MIFVS) difference scheme with a modified k-e model. After validation against an experimental underexpanded jet-flow test cast, the code was applied to two biolistic configurations. Firstly, calculated pressure histories were compared with corresponding measurements in an unsilenced biolistic device, with good agreement. Secondly, this calculation was extended to a silenced geometry, with an emphasis on the gas properties immediately above a skin target. A peak stagnation gas temperature of 420°C is revealed within 175 μs of diaphragm rupture. The temperature of the following driver helium gas suddenly drops to below - 100°C before approaching ambient temperature within 1 ms. The effect of this impinging jet on the human skin is subsequently explored by a one-dimensional convection heat transfer model. On the skin surface, a peak fluctuation of [+5.5°C, - 4.5°C] is.recorded during the operation process. Beyond the outer skin layer, called the stratum corneum (i.e. > 10.6μ), temperature deviations from the normal condition are trivial. Therefore, the heat transfer between the biolistic jet and skin is negligible. This result is consistent with pain-free clinical trial observations.

Potential of microneedle-assisted micro-particle delivery by gene guns: a review

“…The velocity of polymeric micro-particles of 15.5 mm diameter only reaches 330 m/s at 60 bar for the LGG system (Mitchell et al, 2003). Kis et al (2012) have concluded that the particle velocity reached about 700 m/s for CST and range from 200 to 800 m/s for converging-diverging nozzles (Quinlan et al, 2001;Kendall, 2002;Liu & Kendall, 2004b). Recently, Menezes et al (2012) have operated an advanced laser plasma jet to drive gold micro-particles of 1 mm diameter to achieve an average velocity of 1100 m/s within a distance of only 10 mm.…”

Needle-Free Vaccine Injection

“…5), was conceived and developed (Kendall 2002;Liu and Kendall 2004a;Hardy and Kendall 2005;Marrion et al 2005;Truong et al 2006;Liu et al 2007). The devices operate with the principle of delivering a payload of microparticles to the skin with a narrow range of velocities, by entraining the drug payload in a quasi-one-dimensional, steady supersonic flowfield.…”

An efficient numerical method for highly loaded transonic cascade flow

“…It has been demonstrated that the current implicit formulation is adequately efficient when applied to FVS methods, while maintaining a high level of robustness and accuracy [7][8][9]12]. Compared with conventional implicit methods, the MIFVS is a Jacobian spectral-radius scheme and a nonapproximate-factorization scheme.…”

“…The semi-discrete delta expression for Eq. 1 also applicable to (2) of the low-Reynolds-number k-ε model, is derived as in [7,8] …”

“…In this paper, a well-established numerical code, the modified implicit flux-vector-splitting solver (MIFVS) [7][8][9], is employed to investigate such transonic flow in a highly loaded VKI turbine guide-vane cascade [10,11]. This code has been developed and applied to various other flows, with many advantages in terms of accuracy, convergence and computing cost [7,9,12,13].…”