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Pushing Mechanics to the Up Front of Design

Xiao-Yan Gong's picture

When a mechanical engineer and a material scientist were asked for the root cause of an in-vivo fracture. Mechanical engineer pointed to the loading and the material scientist pointed to the processing. While they both are correct, they both also missed the real ROOT cause, the design.

It is very common that medical device design engineers are so focused on the device functionality that often the very basic mechanics is overlooked. Lack of knowledge on the in-vivo environment (Design Requirements) is another subject to blame. However, it is common that even technology driven companies have gaps between design department and duarability deparment. Up front design engineers do not necessarily keep up with the fast paces of material advances. On the other hand, downstram subject matter experts, device tesing teams or often the R&D departments are not informed of design changes before the design is fixed. The problem is worse often in industrial leaders than in start-ups, but the sympton is the same, problem found in animal studies and/or clinical trials before they reached industrial subject matter experts.

Time to change. Mechanics, including device durability need to be taken into consideration in the early design phase. To many companies, it is cheaper to analyze before actually build the parts. Medical Implant Mechanics LLC is formed to fullfil this demand because we truely believe this is the most cost-effective route to more reliable product. Mechanics is science, it helps.

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Zhigang Suo's picture

Xiao-Yan:

This post, as well as your earlier post, Mechanics in Medical Implant Industry, is very helpful to us at universities. They point to a rich field that few of us know much about. One of my new PhD students came in yesterday to say that he would love to work on your problems. He was showing me a printout of your post!

As you know, we at universities have limited resources and time, just like everyone else. Each one of us cannot afford to do many things at the same time. Before we commit to anything, we do what academics do: we read background materials, and try to link new problems to our old strengths.

You will find more willing and effective collaborators if you give us some references to the problem. For example, do you have a reference to the industrial poll on Nitinol fatigue, which you alluded to in your comment?

We would love to read more and in depth of your writings on this exiting topic. To save your time, perhaps you can upload some preprints.  Of course, you can always make hyperlinks or cite journal paper.

Xiao-Yan Gong's picture

Zhigang,

This is the link to NDC's paper on Nitinol fatigue.  http://www.nitinol.info/pdf_files/001.pdf

I will upload my collection of Nitinol fatigue and papers to my web site and let you know as soon as I have it done.  The poll result came from "Stent Summit 06" conference at Cleveland Clinic in August 2006.

This link takes you to the ASTM fatigue to fracture and beyond task group's file archieve and tell you the stent industry's activity on this subject.  If you have trouble to access it, please let me know.

http://finance.groups.yahoo.com/group/allmembersASTMF043006/files/Fatigue%20to%20Fracture%20and%20Beyond%20task%20group/

Xiao-Yan Gong, PhD

Dear all,

I've read your interesting comments concerning Fatigue tests and Nitinol stent topics. As you know there are several concenrs from the medical field about which fatigue test should be performed (radial cpmpression and/or bending and/or axial compression and/or torsion) with nitinol stents for peripheral application. As, mechanical engineer working with physicians I try to get from them "real data and values". I mean, which is the bending value of the arteries, axial compression and so on.

You all, as expert in such interesting field, could you please, which Fatigue test you think should ne necessary to perform and which loading conditions

 my best regards and I looking forward hearing soon from you

 iker

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