Biomimetics and Biomimicry in Engineering

Archive for the ‘Publications’ Category

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.


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).

Applying International Standards to manage comfort

In Publications on 2017/03/01 at 6:46 pm

Have you ever seen the seat testing device at IKEA? We have used a very similar one in our study.


IKEA durability test

Open cell polymeric foams can be tailored so that the support provided and the level of stability is customised to people’s needs. For those who are bed bound or wheelchair users the selection of a cushion can improve their health and general well being. Avoiding pressure points, managing sores and permitting air permeability are the three main design specifications that patients and clinicians aim to when choosing a cushion. In addition to that, a functional cushion, such as those who support lateral movements (e.g. leaning sideways to grab a glass of water and be helped to return to your initial position without compromising one’s stability) and protect from vibration and impacts (e.g. dropping off a curb), are the focus of our last research project.

My team and I have had the privilege to work with the biomechanics and physiotherapists at the SMART Centre at Astley Ainslie Hospital in Edinburgh to study how we can help their clinician colleagues understand cushion performance and therefore aid them with the prescription of these to patients and users.

The results from our study have been presented at the PMG 2012 Conference and recently published by the Assistive Technology journal (free e-prints can be collected here). This has allowed us to interact with the community that is preparing the new version of the ISO16840-2:2007 which will regulate developments in this area.


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.


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


Information Design Journal 2016 volume 22 no. 1


Doing more with less: Bio-inspired innovations

In Comment, Publications on 2016/10/19 at 1:08 pm

The very prestigious Queen Elizabeth Prize for Engineering has invited me to contribute to their blog this month. October is dedicated to exploring the future of Manufacturing and they wanted to hear my story about the work we do in porosity tailored structures inspired by nature. It is a great honour to be showcased by them.

You can read the post here:

Or here:

The Queen Elizabeth Prize for Engineering is a £1million prize fund awarded to an engineer, or group of engineers, whose innovation has been of global benefit to humanity. Alongside awarding the prize, the QEPrize foundation also exists to celebrate and promote engineering, encouraging the next generation to take up the challenges of tomorrow.

Engineered metal implants to target cancer cells and eradicate side effects of chemotheraphy

In Publications on 2014/03/06 at 12:12 am

The work done by my colleague Dr Asier Unciti-Broceta and our ‘dream team’ has been published in Nature Communications.

Asier proudly presents to the world the work done using his clever “bioorthogonal” method for activating a prodrug by palladium catalyzed dealkylation. What motivates us is to move towards the eradication of the side effects of chemotheraphy (e.g. depleted immune system, hair loss, tiredness, etc) in the very near future. This is done by focusing the cancer treatment only to the affected area. Like a ‘trojan horse’, in our vision we implant the engineered catalyst carrier first. Then, by a selective activation via oral drugs, we produce the chemo-destructive effect with maximum effect on the targeted area, and minimal negative effects (i.e. death) on healthy tissue.

The technology in a 'nutshell'

The technology in a ‘nutshell’

The full paper can be found here.

The press release by University of Edinburgh can be viewed here.

Asier is an academic fellow at the Edinburgh Cancer Research UK Centre at the MRC Institute of Genetics and Molecular Medicine, the University of Edinburgh.

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 

Best Free Paper for our work on Prosthetic Devices

In Knowledge Transfer, Publications, Seminars and Keynotes on 2012/04/23 at 11:47 am

Our collaborators Susan Hillman and James Hollington, from the SMART Centre, NHS Scotland, have been awarded Best Free Paper for our  ‘Clinical Interpretation of ISO 16840-2, Measurements for Wheelchair Seating Cushions’ presentation at the Posture and Mobility Group (PMG) National Training Event.

Their stand also attracted a lot of interest from clinicians, manufacturers and the ISO and BSI committees.

James at the stand with clinicians

This collaborative project is focused on checking the clinical relevance of the BS ISO standard 1640-2:2007 on Wheelchair seating for the determination of physical and mechanical characteristics of devices intended to manage tissue integrity, in this case, wheelchair seat cushions. Our paper can be read here: PMG 2012.

Susan and James discussing our work with colleagues

Congratulations Susan and James!

(More info about the centre)

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

International Journal of Design Engineering – Special issue on ‘Design in Nature’

In Publications on 2011/07/25 at 10:25 am

The International Journal of Design Engineering (IJDE) has just published its Special Issue on Design in Nature.

I am very honoured to have my work included there. For this special occasion, i wanted to show-case the developments on a novel manufacturing method for cellular materials with a graded porosity distribution.

The motivation for creating a gradient of porosity in materials has been inspired by nature and aspires to mimic natural structures so their intrinsic advantages (e.g., optimised mechanical properties) can be exploited. Many engineering applications (e.g., thermal, acoustics, mechanical, structural and tissue engineering) require porosity tailored structures. However, current manufacturing processes are currently unable to mass-produce these foams. In this work, low power-low frequency ultrasonic irradiation has been used to excite polymeric foaming melts that, once solidified, contained different porosity distributions throughout in their solid matrix. This was possible by controlling the amount of energy imposed on the samples. The generation of porosity gradients that resembles those of natural cellular structures (e.g., bones, stems) opens up new opportunities in the design and manufacture of bio-inspired materials that can solve challenging technological problems.

Torres-Sanchez, C. et al. (2011) ‘A novel manufacturing strategy for bio-inspired cellular structures’, Int. J. Design Engineering, Vol. 4, No. 1, pp.5–22. DOI:  10.1504/IJDE.2011.041406. A copy can be found here and here.

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.