Vol. 6, No. 1-4, 2011

Download this article
Download this article For screen
For printing
Recent Issues

Volume 12
Issue 3, 249–351
Issue 2, 147–247
Issue 1, 1–146

Volume 11, 5 issues

Volume 10, 5 issues

Volume 9, 5 issues

Volume 8, 8 issues

Volume 7, 10 issues

Volume 6, 9 issues

Volume 5, 6 issues

Volume 4, 10 issues

Volume 3, 10 issues

Volume 2, 10 issues

Volume 1, 8 issues

The Journal
Editorial Board
Research Statement
Scientific Advantage
Submission Guidelines
Submission Form
Author Index
To Appear
ISSN: 1559-3959
Deep penetration and liquid injection into adipose tissue

Kerstyn Comley and Norman Fleck

Vol. 6 (2011), No. 1-4, 127–140

The subcutaneous injection of porcine adipose tissue by a hypodermic needle involves two stages: tissue penetration followed by the delivery of liquid into the tissue. The force required to penetrate adipose tissue by a series of conically tipped and flat-bottomed circular punches has been measured. Scanning electron microscopy and light microscopy are used to observe the mechanism of crack formation during penetration. The experiments reveal that penetration by either a flat bottomed or 45 conically tipped punch involves the formation of a mode II ring crack. The predicted penetration pressure according to the Shergold–Fleck model (Proc. R. Soc. Lond. A 460 (2004), 3037–3058) is in good agreement with the measured pressure on the punch. The subsequent delivery of liquid into adipose tissue by the hypodermic needle has also been examined: the injection pressure for phosphate buffered saline has been measured for a range of flow rates. X-ray images of the injected liquid suggest that micro-cracks are formed by the fluid pressure within the tissue and this leads to an increase in permeability. A seepage model is developed, based on the Darcy flow law, to relate the volumetric flow rate to the injection delivery pressure. Finally, a model of hydraulic fracture is used to assess the toughness associated with the formation of the micro-cracks during injection.

adipose tissue, soft solids, deep penetration, injection, fracture mechanics, toughness
Received: 18 August 2010
Revised: 20 October 2010
Accepted: 23 October 2010
Published: 28 June 2011
Kerstyn Comley
Cambridge University
Department of Engineering
Trumpington Road
Cambridge  CB2 1PZ
United Kingdom
Norman Fleck
Cambridge University
Department of Engineering
Trumpington Road
Cambridge  CB2 1PZ
United Kingdom