Biomimetics and Biomimicry in Engineering

Archive for 2017|Yearly archive page

Snowflakes

In Comment on 2017/12/21 at 12:56 pm

Wilson A. Bentley (1865-1931). This gentleman studied the formation of snowflakes under varied conditions of temperature, pressure and relative humidity.

With rather low-tech scientific apparatus (i.e. a simple microscope and rudimentary equipment to control temperature, pressure and % humidity), he created hundreds, if not thousands, of snow crystals. He coined the sentence “no two snowflakes are the same”.

If it is snowing where you are now, look out of the window and pay attention to the snowflakes. It is not that all the different snowflakes that you see falling from the sky are all absolutely unique and different. His claim means that, under specific atmospheric and physical conditions (i.e. T, P, %hum, altitude, etc), one and only one type of snow crystal will form, and then fall onto the ground.

These images are original photographs taken by Bentley himself using his microscope. The crispness of the images is breathtaking and the beauty of the fractals extraordinary. Enjoy! For example, when snowflakes crystallises with the shape of a tube or a needle, fall to the ground and form a layer of snow on a mountain, that layer may be the precursor in the formation of avalanches.

Bentley’s pioneering work has helped geophysicists and engineers understand ice formations and how to prevent catastrophes. However, there are many questions still unsolved! Snowflakes grow as thin plates, but if the temperature varies only a few degrees, they evolve into long thin crystals. No one knows why.

This last image belongs to a collection from SnowCrystals.com and a beautiful classification of the different types of snowflakes can be seen here.

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Lab diaries: Multifunctional microstructures

In Comment on 2017/12/12 at 1:18 pm

We have created new structures that provide comfortable accommodation for bone-forming cells. We seeded them, puffed up their pillows, fed them with their favourite food and drink and waited. The other day we went to check on them. This one looks particularly pleased!

Mock up

When we fixed the cells we found this shape, decorated with eyes (prob debris from the desiccating chemicals) which we have decorated with a tie

We are functionalising surfaces to tune them to chemical bio markers and embedding intelligence to create active structures and welcoming new homes for cell cultures. Attention to detail: we even decorate their sitting spaces with flowers

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Mechanical behaviour that mimics that of cortical and trabecular bones

In Publications on 2017/11/30 at 11:22 am

We have published our most recent results on how porosity and pore size affect both mechanical properties and biological response of osteoblastic cells on titanium porous structures.

Working with volumetric porosities that match those of cortical and trabecular bone, we finely controlled the pore size in the substrate with the aim to assess how a variation in pore size can tailor mechanical properties (i.e. stiffness and strength). Furthermore, we report how we could establish regressions that would allow us to create a design tool based on porosity, so it would return the desired mechanical properties values.

From a bioengineering viewpoint, the results from this study showed that scaffolds with the lowest pore range (45-106um) presented the largest number of cells attached in the early days  (day 1 and  3) indicating this microarchitecture was the best indicated for cell attachment. Pore range >300 mm exhibited the most favourable conditions for cell proliferation, surpassing those on the control samples. The viability of scaffolds with pore size 212-300um was the poorest, indicating these scaffolds do not promote cell proliferation for osteosarcoma osteoblasts due to the distance the cells had to span.

Proliferation_supplementary

Proliferation data from the osteoblasts on titanium porous (A,B 1-4) and non-porous (Ti) normalised to the previous timepoint of culture (in/in-1, n=3, 7, 12); as it appears in https://www.ncbi.nlm.nih.gov/pubmed/28532024

The study can be found here in the Materials Science and Engineering C: Materials for Biological Applications.

Removing mass with maths

In Comment on 2017/11/14 at 3:02 pm

We are creating lightweight materials by removing mass from where it is not needed and adding it to places subjected to high loads and strains. It is Drawing with Maths

“[The Universe] is written in the language of mathematics, and its characters are triangles, circles and other geometrical figures, without which it is humanly impossible to understand a single word of it” —Galileo Galilei, The Controversy on the Comets, 1618

Engineered foams for wheelchair seating

In Publications on 2017/11/08 at 10:39 am

We have published the results arising from our studies on open cell polymeric foams that can be tailored so that they support those who are bed bound or wheelchair users providing them with general well being and alleviating pressure points.

Avoiding pressure points, managing sores and permitting air permeability are the three main design specifications that 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 research project.

The Multifunctional Materials Lab and clinicians from the NHS have studied 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 published in the Medical Engineering and Physics Journal and in the Assistive Technology Journal .

The International Standard that regulates developments in this topic is the ISO16840-2:2007, which is currently under revision. We are hoping our work to inform their work and assist in their revisions for the replacement ISO 16840-2.

iso_replacement

 

Porosity and pore size effect on the properties of sintered Ti35Nb4Sn alloy scaffolds and their suitability for tissue engineering applications

In Publications on 2017/11/03 at 11:04 am

Our most recent results on the importance of tailoring porosity engineered materials for cell regeneration are to be published in the Journal of Alloys and Compounds.

Porous scaffolds manufactured via powder metallurgy and sintering were designed for their structure (i.e. pore size and porosity) and mechanical properties (stiffness, strength) to be controlled and tailored to mimic those of human bone. The scaffolds were realised to fulfill three main objectives:

(i) to obtain values of stiffness and strength similar to those of trabecular (or spongy) bone, with a view of exploiting these as bone grafts that permit cell regeneration,

(ii) to establish a relationship between stiffness, strength and density that allows tailoring for mass customisation to suit patient’s needs; and

(iii) to assess alloy cytotoxicity and biocompatibility via in vitro studies.

The results obtained using a very low stiffness alloy (Ti35Nb4Sn) further lowered with the introduction of nominal porosity (30–70%) with pores in the ranges 180–300 μm and 300–500 μm showed compatibility for anatomical locations typically subjected to implantation and bone grafting (femoral head and proximal tibia). The regression fitting parameters for the linear and power law regressions were similar to those found for bone specimens, confirming a structure favourable to capillary network formation. Biological tests confirmed non-cytotoxicity of the alloy.

Scaffolds of porosity nominal 50%vol and pore range 300–500 μm performed best in the adhesion and propagation assays due to a good balance between surface area and pore cavity volume.

Graphical abstract for https://doi.org/10.1016/j.jallcom.2017.10.026

Study on bio-mechanical properties of porosity scaffolds tailored for cell regeneration, https://doi.org/10.1016/j.jallcom.2017.10.026

A pre-view of the article appears on Journal of Alloys and Compounds, Volume 731, 15 January 2018, Pages 189-199, https://doi.org/10.1016/j.jallcom.2017.10.026.

 

The effect of pore size and porosity on mechanical properties and biological response of porous titanium scaffolds

In Publications on 2017/10/27 at 8:49 am

The Multifunctional Materials Lab has recently published our results on porosity tailored titanium scaffolds. The results were very interesting and demonstrated there is more to what the eye can see in a first pass: cells are extremely sensitive to cavities and ‘think’ about whether they should bridge a gap or simply fill the hole.

Our article can be found here

The effect of pore size and porosity on elastic modulus, strength, cell attachment and cell proliferation was studied for Ti porous scaffolds manufactured via powder metallurgy and sintering. Porous scaffolds were prepared in two ranges of porosities so that their mechanical properties could mimic those of cortical and trabecular bone respectively. Space-holder engineered pore size distributions were carefully determined to study the impact that small changes in pore size may have on mechanical and biological behaviour. The Young’s moduli and compressive strengths were correlated with the relative porosity. Linear, power and exponential regressions were studied to confirm the predictability in the characterisation of the manufactured scaffolds and therefore establish them as a design tool for customisation of devices to suit patients’ needs. The correlations were stronger for the linear and the power law regressions and poor for the exponential regressions. The optimal pore microarchitecture (i.e. pore size and porosity) for scaffolds to be used in bone grafting for cortical bone was set to < 212 μm with volumetric porosity values of 27–37%, and for trabecular tissues to 300–500 μm with volumetric porosity values of 54–58%. The pore size range 212–300 μm with volumetric porosity values of 38–56% was reported as the least favourable to cell proliferation in the longitudinal study of 12 days of incubation.

https://doi.org/10.1016/j.msec.2017.03.249

Cells are sensitive to small changes in pore size and some are even detrimental to their proliferation. https://doi.org/10.1016/j.msec.2017.03.249

Published in Materials Science and Engineering: C, Volume 77, 1 August 2017, Pages 219-228, https://doi.org/10.1016/j.msec.2017.03.249

3D Acoustic-Structure Interaction of Ultrasound in Fluids for the Manufacture of Graded Materials

In Publications, Seminars and Keynotes on 2017/10/20 at 2:55 pm

Functionally graded materials engineered to meet specific requirements are being increasingly sought after for advanced engineering projects, yet the possibilities for their manufacture lag behind their design. The ability to control the porosity of a cellular material is one such method for adding functional gradients within materials. A novel
technique using ultrasound to control the porosity in reacting polymers shows potential to effectively mass-manufacture porosity tailored polymeric foams. In this work the pressure field in a metastable polymer produced by multiple ultrasonic sources is
modeled at distinct stages of the polymerisation reaction.

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Joe Holt presenting our work on multiphysics modelling

This work has been presented at the COMSOL Conference 2017, 18th – 20th October 2017, Rotterdam (Netherlands) by Joe Holt, a researcher in the Multifunctional Materials Manufacturing Lab, PhD student of the EPSRC Centre for Doctoral Training in Embedded Intelligence and co-sponsored by FAR Composites UK Ltd.

Transition Zone Training: 2017 Summer School #SSEI17

In Info, Seminars and Keynotes on 2017/06/25 at 6:34 pm

The Transition Zone Training Programme is holding a Summer School in Loughborough University London from the 3rd to the 6th July in the Queen Elizabeth Olympic Park, London.

Innovation insights for the digital workforce of tomorrow is the 4-day event organised by the EPSRC CDT in Embedded Intelligence in partnership with the Digital Economy Network and attended by the UK community of practice in Digital Manufacturing, Robotics, Big Data, Cybersecurity and the Internet of Things.

location

A much-provoking Panel discussion to address the digital skills gap and the role PhD students play in the knowledge economy will kick-start the #SSEI17: ‘Aligning skills to jobs for the digital future of the knowledge society’. Chaired by Dr S Barr, head of The Manufacturer, brings together industrialists and entrepreneurs (the MTC, HSSMI, Block Solutions), postgraduate educators (Loughborough University) and funding bodies (EPRSC). Seminars, workshops and practicals will be facilitated by world-class innovators and practitioners who are bringing to us the latest in Cybersecurity, Robotics, Computational Thinking, Data visualisation, Film making, and fostering of Creative thinking through Serious Games. Attending to the ethos of a Transition Zone activity, there will be time for the honing of effective communication skills focusing on personal brand.

The programme for the event can be viewed here: CDT-EI Summerschool programme 2017 prf3.2

You can follow the event online: on Facebook: CDT-EI, DEN Digital Economy CDT Network; on Twitter: @cdt-ei, @decdtnetwork, @carmentorres

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).