Measurements of the gas and particle flow within a converging-diverging
nozzle for high speed powdered vaccine and drug delivery
M. A. F. Kendall, N. J. Quinlan, S. J. Thorpe, R. W. Ainsworth, B. J. Bellhouse
Abstract A unique system has been developed based upon
the concept of accelerating pharmaceutical agents in particle
form with a gas ﬂow to attain sufﬁcient momentum to enter
the epidermis of human skin and achieve a pharmacological
endpoint. This paper presents an experimental investigation
of the transient gas and particle dynamics within a transonic
converging-diverging nozzle prototype. The primary gas
ﬂow regimes are identiﬁed through Pitot-static pressure
surveys and schlieren images with a high frame rate. The
action of the gas ﬂow-ﬁeld in imparting momentum to the
drug particles is investigated through schlieren imaging
and time-resolved Doppler global velocimetry (DGV).
DGV Doppler global velocimetry
CCD Charge coupled device
CST Contoured shock tube
Intradermal powder injection is a novel technology for
needle-free administration of a range of vaccines and drugs.
Although liquid injection through needle and syringe is
simple, versatile, inexpensive and widely used, it is disliked
by many patients and entails risks of contamination and
injury. Alternatives including liquid jet injectors, creams,
diffusion patches and pulmonary systems have been
developed with varied advantages and limitations. Intra-
dermal powder injection is a relatively new needle-free
technology, in which particles containing vaccines (and
drugs) are accelerated to sufﬁcient momentum to penetrate
the skin and achieve a pharmacological effect. Sanford et al.
(1990) pioneered this innovation with systems designed to
deliver DNA coated metal particles (with diameter of the
order of 1 lm) into plant cells for genetic modiﬁcation
using pistons accelerated along the barrels of adapted guns.
The concept was extended by Bellhouse et al. (1994) to the
treatment of humans with particles accelerated by
entrainment in a supersonic gas ﬂow. Prototype devices
embodying this concept have been shown to be effective,
painless, and applicable to pharmaceutical therapies rang-
ing from protein delivery (Burkoth et al. 1999) to conven-
tional (Chen et al. 2000) and DNA vaccines (Lesinski et al.
2001). Derivatives of these prototypes are in commercial
development for clinical use in humans under the name
Dermal PowderJect; an example is illustrated in Fig. 1.
To achieve the concept’s full potential in a range of
pharmaceutical applications, a thorough understanding of
the gas-particle dynamics is required. Studies have been
performed on simpliﬁed prototype systems to meet this end.
The ﬁrst steps toward developing this understanding
consisted of a measurement programme in which static
pressures and time-integrated Doppler global velocimetry
(DGV) measurements of drug particle velocity were
acquired in a simpliﬁed device (Quinlan 1999; Quinlan
et al. 2001). These measurements were useful, but gave an
incomplete description of the predominantly unsteady
ﬂow in the device.
In this paper, the results of an extended experimental
investigation of the transient gas and particle dynamics
within a prototype intradermal particle delivery system are
presented. The primary gas ﬂow regimes are identiﬁed
from Pitot-static pressure surveys and schlieren images.
The action of the gas ﬂow-ﬁeld in imparting momentum to
vaccine or drug particles is quantiﬁed with time-resolved
DGV measurements. The experimental data are analysed
collectively and lead to a discussion of the relative effects of
different gas ﬂow regimes on the particle momentum dis-
tribution throughout the nozzle. Finally, the implications of
these ﬁndings for biological performance of the system and
for the direction of future developments are discussed.
Device geometry and operating conditions
The focus of this study is on a prototype vaccine delivery
system simpler in construction than the device used in
clinical applications illustrated in Fig. 1. Key components
Experiments in Fluids 37 (2004) 128–136
Received: 21 June 2002 / Accepted: 15 December 2003
Published online: 21 April 2004
Ó Springer-Verlag 2004
M. A. F. Kendall (&), S. J. Thorpe, R. W. Ainsworth, B. J. Bellhouse
Department of Engineering Science, University of Oxford, UK
N. J. Quinlan
Department of Mechanical and Biomedical Engineering,
National University of Ireland, Galway, Republic of Ireland
M.A.F Kendall and N.J. Quinlan contributed equally to this paper.
Some of this work was originally presented at the 22nd Interna-
tional Symposium on Shock Waves, Imperial College, London, UK.
The authors thank PowderJect Pharmaceuticals Plc for its support
of this work, the EPSRC instrument loan pool for the Kodak
HS4540 Camera, EPSRC grant GR/JS4307 for the DGV work and
Terry Jones for making available schlieren equipment at the
Southwell Laboratory within the University of Oxford.