Biomimetics and Biomimicry in Engineering

Posts Tagged ‘journals’

Mathematical modelling of sonicated bubbles

In Publications on 2017/05/31 at 5:10 pm

One possible manufacturing method for bone scaffolds used in regenerative medicine involves the acoustic irradiation of a reacting polymer foam to generate a graded porosity. Sonication of foams have been our focus of research for many years now as this technology allows the porosity tailoring of cellular materials.

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Sonicated foam (energy received from the left) with a marked gradation in porosity

We have joined forces with Prof Mulholland’s team (Dr Barlow and Dr Bradley) at Strathclyde University and worked on a mathematical model of a non-reacting process in order to develop theoretical confirmation of the influence of the acoustic signal on the polymer foam.

The model describes single bubble growth in a free rising, nonreacting polymer foam irradiated by an acoustic standing wave and incorporates the effects of inertia. Investigations are carried out to explore the influence of inertia on the bubble volume, fluid pressure and the stress tensors of the foam, and to explore the effect of fluid viscosity and acoustic pressure amplitude on the final bubble volume, and the curing time. A key result is that increasing the applied acoustic pressure is shown to result in a reduced steady state bubble volume, indicating that ultrasonic irradiation has the potential to produce tailored porosity profiles in cellular materials such as bioengineering scaffolds and light-weight structures.

Our work has been compiled as a paper recently published in the Journal of Non-Newtonian Fluid Mechanics and can be found here (Open Access).

Empowering resilient communities

In Publications on 2017/02/06 at 10:58 pm

We have created low-cost housing solutions for the local community in Pabal (India). Those people have a lot of ingenuity but not a lot of money to buy expensive building materials. Only the transport to their villages would cost them a significant amount.

But they have a wealth of natural resources. And amongst them, they have bamboo, a fascinating multifunctional material, ideal for structure-erecting, wind-loading and vibration-proofing due to its heterogeneous porous structure and high shear modulus.

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Bamboo: macro and microstructure

We have helped them to build those modular huts by providing them with a set of instructions that are universal and accessible to all, no matter the mother tongue, ability or building skills. In this way they are prepared to adapt and be resilient to the threats posed by natural forces and climate change hazards (e.g. floods, pluvial, wind, earth tremors) and reinforce their coping strategy as a resilient community.

In the process of developing those instructions we have learnt a lot from the Information Design community. There is so much lo learn about user-centric design, cognitive load and the language of actions, perspectives and colours to convey instructions and allow self-guidance. I deeply thank them for having mentored us.

Our work can be read here and directly on the Information Design Journal site

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Information Design Journal 2016 volume 22 no. 1

 

Making sense of standardisation

In Publications on 2013/11/18 at 12:27 am

Standardisation is that useful process that allows us engineers to share a common ‘plane of reference’ on which to base our conversations. It is useful to know that a material (say, a slab of titanium) has the same mechanical properties when it is measured in Loughborough, Sydney, Lima or Granada.

But sometimes standardisation goes too far on the other extreme. The over-translation from observation to technical definitions might turn an ISO norm into a document that is no longer useful for practical purposes. This is particularly risky when ISO norms attempt to tabulate and measure in ‘softer’ areas such as healthcare and rehabilitation.

In a piece of work recently published here, my colleagues from the NHS Scotland SMART Centre and we have restated some practical insight to an ISO norm that guides the characterisation of wheelchair cushions for a better guidance to prescription by clinicians.

Our work has been well received by the practising community and we look forward to continue working with them.

Ref: Hollington J., Hillman S.J., Torres-Sanchez C., Boeckx J., Crossan N., “ISO 16840-2:2007 load deflection and hysteresis measurements for a sample of wheelchair seating cushions”, Medical Engineering & Physics, in press. DOI:10.1016/j.medengphy.2013.10.010 

Emulating nature for better engineering – Inderscience news release

In Publications on 2011/07/29 at 8:50 am

Inderscience has published here a news release where my newest article on Design by Nature has been covered. The article appears in AlphaGalileo, the world’s independent source of research news.

Emulating nature for better engineering

28 July 2011 by Inderscience

UK researchers describe a novel approach to making porous materials, solid foams, more like their counterparts in the natural world, including bone and wood in the new issue of the International Journal of Design Engineering.

According to Carmen Torres-Sanchez of the Department of Mechanical Engineering, at Heriot-Watt University, Edinburgh and Jonathan Corney of the Department of Design, Manufacture and Engineering Management, at the University of Strathclyde, Glasgow in the natural world, the graduated distribution of porosity has evolved so that nature might transfer forces and minimise stresses to avoid whole structure failure. For instance, a crack in the branch of a tree will not lead to the felling of the tree in the same way that a broken ankle will not lead to collapse of the whole leg. “Porosity gradation is an important functionality of the original structure that evolution has developed in a trial and error fashion,” the team explains.

It is not just tree trunks and bones that have evolved graduated porosity, beehives, marine sponges, seashells, teeth, feathers and countless other examples display this characteristic. Researchers would like to be able to emulate the way in which nature has evolved solutions to the perennial issues facing engineers. In so doing, they will be able to develop structures that use the least amount of material to gain the lowest density structure and so the maximum strength-to-weight ratio.

“Many engineering applications, such as thermal, acoustics, mechanical, structural and tissue engineering, require porosity tailored structures,” the team says. If materials scientists could develop porous materials that closely mimic nature’s structural marvels, then countless engineering problems including bridge building and construction in earthquake zones, improved vehicle and aircraft efficiency and even longer-lasting more biocompatible medical prosthetics might be possible.

Unfortunately, current manufacturing methods for making porous materials cannot mass-produce graduated foams. The collaborators in Scotland, however, have turned to low power-low frequency ultrasonic irradiation that can “excite” molten polymers as they begin to foam and once solidify effectively trap within their porous structure different porosity distributions throughout the solid matrix. This approach allowed the team to generate polymeric foams with porosity gradients closely resembling natural cellular structures, such as bones and wood. The technology opens up new opportunities in the design and manufacture of bio-mimetic materials that can solve challenging technological problems, the team adds.

The researchers anticipate that using more sophisticated ultrasound energy sources as well as chemical coupling agents in the molten starting material will allow them to fine tune the formation of pores in the material. This is an area of current interest because it would facilitate the design of novel texture distributions or replicate more closely nature porous materials, the team concludes.

  • Full bibliographic information“A novel manufacturing strategy for bio-inspired cellular structures” in Int. J. Design Eng., 2011, 4, 1, 5-22

Wobbly rulers and elastic strings: how to measure change

In Publications on 2011/02/21 at 10:52 am

My work on the characterisation of density engineered foams fabricated with ultrasound has been published recently in the Journal of Material Science (vol 46, no. 2)

This is ongoing work on one of my favourite research topics: how can macroscopic properties be extrapolated from microscopic characteristics.

In particular, this piece of work deals with the lack of measurement techniques available for functionally tailored materials. Traditionally, we have measured material’s bulk values: Young’s moduli, Poisson’s ratios, densities, etc. We assumed the material was homogeneous and isotropic, equally distributed.

But how homogeneous can a material be if you look close enough?

Especially when dealing with natural materials such as bones or plant stems. How homogeneous is homogeneous?  It is not, is it? And if it is heterogeneous, how do you measure, quantify that property? Bulk values are no longer valid, and a new strategy for the measurement of engineered or tailored materials has to be thought of.

I present a new systematic way in an attempt to start cracking this challenge that Biomimetics holds. And the work continues.

Highlighted article in prestigious IOP collection

In Publications on 2010/05/25 at 5:09 pm

My article “Porosity tailoring mechanisms in sonicated polymeric foams”, published in September 2009 (2009 Smart Mater. Struct. 18 104001; doi: 10.1088/0964-1726/18/10/104001) has been included in the collection of highlight articles published in 2009 in Smart Materials and Structures, an IOP Journal.

The importance of engineering functionally graded cellular microstructures and the motivation behind the creation of a flexible manufacturing process are the main topics of this article.  In particular, this paper reports how the manufacture of polymeric foams with a variable porosity distribution can be achieved by ultrasound irradiation during the ‘sensitive’ stages of the polymerization reaction. The energy and mass balances were studied for each of the five distinctive stages of polymerization (i.e. cream, rising, packing, gelation and solidification) in order to determine the underlying mechanisms that ultrasound employs to affect the reaction. It was concluded that controlled ultrasonic irradiation affects convective mass transfer during foaming, especially during ‘rising’ and ‘packing’ stages, and enhances the diffusion of the blowing agent (i.e. CO2(g)) from bubble to bubble in the ‘packing’ and ‘gelation’ stages. The mechanical work put into the system by ultrasound assists both the convection and diffusion by increasing the rate of mass flux. The paper concludes with experimental results that support the above hypotheses.

These findings are of great importance for the optimisation of manufacturing processes of functionally tailored materials for ‘ad-hoc’ applications, such as biomaterials, orthopaedics, medical devices or high-tech structures (e.g. aerospace, automobile).

The full collection can be found here:  http://iopscience.iop.org/0964-1726/page/Highlights of 2009

My featured article here (SmartMatStruct_09_Mechanism_porosity_tailoring_Torres-Sanchez) and here: http://iopscience.iop.org/0964-1726/18/10/104001

Crowdsourcing publications

In Publications on 2010/04/02 at 4:49 pm

The team has been busy in the last few weeks and our efforts have crystallized into Journal and Conference papers.

“Putting the crowd to work in the knowledge-based factory” has been accepted for publication in to the Advanced Engineering Informatics Journal, special issue on the Cognitive Factory; and  “Outsourcing labour to the Cloud” is accepted for publication in the general issue of the International Journal of Innovation and Sustainable Development.

Paola DiMaio will present in Dubai our paper on Library Searches, a joint project with the National Library of Scotland: “Towards Crowdsourcing translation tasks in library cataloguing”, IEEE International Conference on Digital Ecosystems and Technology (DEST), Special Track on  “Web Based Harnessing of Human Collective Intelligence”, 12-15 April 2010, Dubai, United Arab Emirates.

Check the ‘Publications’ section for full details on these and other publications