Interdisciplinary research: Easy, or hard?

Interdisciplinary research: Easy, or hard?

J O U R N A L O F T H E M E C H A N I C A L B E H AV I O R O F B I O M E D I C A L M AT E R I A L S 2 (2009) 1–2 available at www.sciencedirect.com ...

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J O U R N A L O F T H E M E C H A N I C A L B E H AV I O R O F B I O M E D I C A L M AT E R I A L S

2 (2009) 1–2

available at www.sciencedirect.com

journal homepage: www.elsevier.com/locate/jmbbm

Editorial

Interdisciplinary research: Easy, or hard?

In interdisciplinary research, one can sometimes make progress relatively easily. Claus Mattheck said that “the fruit hangs closer to the ground” in these areas (Mattheck, 1998). That’s true, but at the same time there are difficulties and challenges to interdisciplinary research which do not exist in more conventional fields. Research work is a creative activity; creativity is difficult to define, but one definition is the act of putting together two concepts which had never been put together before. In biomechanics that means combining an idea in biology with an idea in mechanics. We can see examples of this kind of original thinking in papers published in the Journal of the Mechanical Behavior of Biomedical Materials. For example, Niinomi (2008) coined the term “mechanical biocompatibility” to express the idea that the mechanical properties of implant materials must be chosen in such a way as to be compatible with those of the natural materials around them: stiffness matching is the most obvious example but the concept has other, more subtle, implications. Other papers have revealed synergies between mechanical and biological factors in experimental studies: for example Nychka et al. (2008) found that residual stress affected the bioactivity of a bioactive glass, whilst Adachi et al. (2008) linked calcium signalling to mechanical deformation at the cellular level. Another definition of creativity is to be able to think the unthinkable: in our world that means leaving aside concepts that seem so obvious that we do not question them. Physics in the twentieth century was able to advance only through the realisation that there is no hard distinction between matter and energy. An example in our own field is the distinction between a material and a structure. Materials scientists are used to developing materials, with measurable properties, which can be supplied in appropriately-sized pieces, from which engineers can make structures. But in Nature there is no such distinction: the material we call cartilage varies drastically in its properties and microstructure within a single joint. Subit et al. (2008) c 2008 Elsevier Ltd. All rights reserved. 1751-6161/$ - see front matter doi:10.1016/j.jmbbm.2008.10.001

described the gradual changes in material structure that occur at the ligament/bone attachment — changes that make sense when one thinks about local stress concentration effects. Less obvious perhaps are the variations in cortical bone anisotropy recently discovered by Espinoza Orias et al. (in press): understanding and explaining these effects will require further research. Another cherished assumption has been challenged by the work of Barak et al. (2009) who asked “Are tensile and compressive Young’s moduli of compact bone different?”. Not all papers in the Journal of the Mechanical Behavior of Biomedical Materials make these creative leaps, and we would not expect them to. But we do insist that they contain two essential aspects: a mechanical property element and a biomedical element. Papers describing material properties must show that the material concerned has a biomedical application, at least potentially, and papers concerned with natural tissues or biomaterials must discuss their mechanical properties. Maybe the fruit does sometimes grow close to the ground, but only if you are standing in the right place. REFERENCES

Adachi, T., Sato, K., Hiqashi, N., Tomita, Y., Hojo, M., 2008. Simultaneous observation of calcium signaling response and membrane deformation due to localized mechanical stimulus in single osteoblast-like cells. Journal of the Mechanical Behavior of Biomedical Materials 1, 43–50. Barak, M.M., Currey, J.D., Weiner, S., Shahar, R., 2009. Are tensile and compressive Young’s moduli of compact bone different? Journal of the Mechanical Behavior of Biomedical Materials 2 (1), 51–60. Espinoza Orias, A.A., Deuerling, J.M., Landrigan, M.D., Renaud, J.E., Roeder, R.K., 2009, Anatomic variation in the elastic anisotropy of cortical bone tissue in the human femur Journal of the Mechanical Behavior of Biomedical Materials, in press (doi:10.1016/jmbbm.2008.08.005). Mattheck, C., 1998. Design in Nature: Learning from Trees. Springer-Verlag, Berlin.

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J O U R N A L O F T H E M E C H A N I C A L B E H AV I O R O F B I O M E D I C A L M AT E R I A L S

Niinomi, M., 2008. Mechanical biocompatibilities of titanium alloys for biomedical applications. Journal of the Mechanical Behavior of Biomedical Materials 1, 30–42. Nychka, J.A., Li, D., Alexander, B., 2008. In vitro bioactivity of 45S5 bioactive glass as a function of indentation load. Journal of the Mechanical Behavior of Biomedical Materials 1, 243–251. Subit, D., Masson, C., Brunet, C., Chabrand, P., 2008. Microstructure of the ligament-to-bone attachment complex in the human

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knee joint. Journal of the Mechanical Behavior of Biomedical Materials 1, 360–367.

David Taylor Trinity Centre for Bioengineering, School of Engineering, Trinity College, Dublin, Ireland E-mail address: [email protected] Published online 15 October 2008