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Pressure and Stress Transients in Autoinjector Devices


Veilleux, Jean-Christophe (2019) Pressure and Stress Transients in Autoinjector Devices. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/VJSH-TF65.


The viscosity of drug solutions delivered parenterally has been increasing over the years. Injecting viscous drug solutions using spring-actuated autoinjector devices is challenging due to a number of technical and human factor constraints. Some of the related challenges are investigated in this thesis.

Actuation of autoinjector devices powered using stiff springs can create deleterious pressure and stress transients which are not needed to achieve the normal functions of the device. Experimental measurements have shown that peak pressures and stresses substantially larger than what is needed to achieve the normal device function can occur during the actuation phase, creating unnecessary potential for device failure.

The acceleration of the syringe during actuation can be very large, often creating transient cavitation in the cone region. The occurrence or absence of cavitation is determined by the relative timing of syringe pressurization and syringe acceleration, which is affected by several factors such as the presence, location, and size of an air gap inside the syringe, and the friction between the plunger-stopper and the syringe.

Experiments and numerical simulations have shown that sharp pressure waves traveling inside the syringe can be amplified within the cone terminating the syringe. Despite the potential for shock focusing, the impulsive pressurization and the rapid deceleration of pre-filled syringes create a potential for failure which is localized in the syringe shoulder and at the junction between the flange and the barrel, not inside the cone. The cavitation events, on the other hand, create a potential for failure which is limited to a region in close proximity of the bubble upon collapse. The collapse of cavitation bubbles located within the syringe cone can be enhanced due to geometrical effects, and the resulting stresses can be large enough to cause syringe failure.

This thesis demonstrates that static and quasi-static analyses do not provide accurate estimates of the peak pressures and stresses occurring within the device. The pressure and stresses created by the highly dynamic events occurring during actuation need to be accounted for during device design in order to improve device reliability, the user's experience, and patient's adherence to prescribed treatments. The findings discussed in this work provide insights and guidance as to how the transient events can be mitigated.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Autoinjector; viscous drug solution; pressure and stress transient; shock focusing; cavitation; bubble dynamics; syringe; syringe failure; damping;
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Aeronautics
Awards:William F. Ballhaus Prize, 2019. Hans G. Hornung Prize, 2019.
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Shepherd, Joseph E.
Group:Explosion Dynamics Laboratory, GALCIT
Thesis Committee:
  • Colonius, Tim (chair)
  • Ravichandran, Guruswami
  • Gharib, Morteza
  • Shepherd, Joseph E.
Defense Date:6 February 2019
Non-Caltech Author Email:jc (AT)
Funding AgencyGrant Number
Record Number:CaltechTHESIS:02172019-174051312
Persistent URL:
Related URLs:
URLURL TypeDescription adapted for Section 1 of Ch. 4. adapted for Ch. 6. adapted for Ch. 1, 2, and 3. application adapted for Ch. 2 and 7. adapted for Section 1 of Ch. 4.
Veilleux, Jean-Christophe0000-0002-5420-9411
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:11395
Deposited By: Jean Christophe Veilleux
Deposited On:22 Feb 2019 16:55
Last Modified:25 Oct 2023 20:58

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