Tag Archives: MyResearch

Salt increases nanoparticle diffusion

About two and half years ago, I wrote about an article we had published on the motion of nanoparticles [see ‘Slow moving nanoparticles‘ on December 13th, 2017] in which we had shown that, for very small particles at low concentrations, the motion of a particle is independent of its size and does not flow the well-known Stokes-Einstein law.  Our article presented convincing evidence from experiments to support our conclusions but was light on explanation in terms of the mechanics.  At the end of last year, we published a short article in Scientific Reports, in which we demonstrated that the motion of nanoparticles at low concentrations is dependent on the interaction of van der Waals forces and electrostatic forces.  Van der Waals forces are short-range attractive forces between uncharged molecules due to interacting dipole moments, whereas the electrostatic forces are the repulsion of electric charges.  We changed both of these forces by using salt solutions of different concentration and observing the changes in nanoparticle behaviour.  Increasing the molarity increases the diffusion of the particles until the solution is saturated, as shown in the picture for 50 nanometre diameter gold particles (that’s about half the diameter of a coronavirus particle or one thousandth of the diameter of a human hair).  Our findings have implications for understanding the behaviour of nanoparticles dispersed in biological media, which typically contain salt in solution, because the concentration of salt ions in the medium affects nanoparticle diffusion that has been shown to influence cellular uptake and toxicity.

Sources:

Coglitore D, Edwardson SP, Macko P, Patterson EA, Whelan MP, Transition from fractional to classical Stokes-Einstein behaviour in simple fluids, Royal Society Open Science, 4:170507, 2017.

Giorgi F, Coglitore D, Curran JM, Gilliland D, Macko P, Whelan M, Worth A & Patterson EA, The influence of inter-particle forces on diffusion at the nanoscale, Scientific Reports, 9:12689, 2019.

Try the impossible to achieve the unusual

Everyone who attends a certain type of English school is given a nickname.  Mine was Floyd Patterson. In 1956, Floyd Patterson was the youngest boxer to become the world heavyweight champion.  I was certainly not a heavyweight but perhaps I was pugnacious in defending myself against larger and older boys.  Floyd Patterson had a maxim that drove his career: ‘you try the impossible to achieve the unusual’.  I have used this approach in various leadership roles and in guiding my research students for many years by encouraging them to throw away caution in planning their PhD programmes.   I only made the connection with Floyd Patterson recently when reading Edward O. Wilson‘s book, ‘Letters to a Young Scientist‘.  Previously, I had associated it with Edmund Hillary’s biography that is titled ‘Nothing Venture, Nothing Win’, which is peculiar corruption of a quote, often attributed to Benjamin Franklin but that probably originated much earlier, ‘Nothing ventured, nothing gained’.  I read Hillary’s book as a young student and was influenced by his statement that ‘even the mediocre can have adventures and even the fearful can achieve’.

Sources:

Edmund Hillary, ‘Nothing Venture, Nothing Win’, The Travel Book Club, London, 1976.

Edward O. Wilson, Letters to a Young Scientist, Liveright Pub. Co., NY, 2013.

The Stone Raft adrift in the Atlantic Ocean

I spent most of last week at the European Union’s Joint Research Centre in Ispra, Italy.  I have been collaborating with the scientists in  the European Union Reference Laboratory for alternatives to animal testing [EURL ECVAM].  We have been working together on tracking nanoparticles and, more recently, on the validity and credibility of models.  Last week I was there to participate in a workshop on Validation and Acceptance of Artificial Intelligence Models in Health.  I presented our work on the credibility matrix and on a set of factors that we have developed for establishing trust in a model and its predictions. I left the JRC on Friday evening and slipped back in the UK just before she left the Europe Union.  The departure of the UK from Europe reminds me of a novel by José Saramago called ‘The Stone Raft‘ in which the Iberian penisula breaks off from the Europe mainland and drifts around the Atlantic ocean.  The bureaucrats in Europe have to run around dealing with the ensuing disruption while five people in Spain and Portugal are drawn together by surreal events on the stone raft adrift in the ocean.

When seeing nothing is a success

In November I went to Zurich twice: once for the workshop that I wrote about last week [see ‘Fake facts and untrustworthy predictions’ on December 4th, 2019]; and, a second time for a progress meeting of the DIMES project [see ‘Finding DIMES’ on February 6th, 2019].  The progress meeting went well.  The project is on schedule and within budget. So, everyone is happy and you are wondering why I am writing about it.  It was what our team was doing around the progress meeting that was exciting.  A few months ago, Airbus delivered a section of an A320 wing to the labs of EMPA who are our project partner in Switzerland, and the team at EMPA has been rigging the wing section for a simple bending test so that we can use it to test the integrated measurement system which we are developing in the DIMES project [see ‘Joining the dots’ on July 10th, 2019].  Before and after the meeting, partners from EMPA, Dantec Dynamics GmbH, Strain Solutions Ltd and my group at the University of Liverpool were installing our prototype systems to monitor the condition of the wing when we apply bending loads to it.  There is some pre-existing damage in the wing that we hope will propagate during the test allowing us to track it with our prototype systems using visible and infra-red spectrum cameras as well as electrical and optical sensors.  The data that we collect during the test will allow us to develop our data processing algorithms and, if necessary, refine the system design.  The final stage of the DIMES project will involve installing a series of our systems in a complete wing undergoing a structural test in the new Airbus Wing Integration Centre (AWIC) in Filton, near Bristol in the UK.  The schedule is ambitious because we will need to install the sensors for our systems in the wing in the first quarter of next year, probably before we have finished all of the tests in EMPA.  However, the test in Bristol probably will not start until the middle of 2020, by which time we will have refined our algorithm for data processing and be ready for the deluge of data that we are likely to receive from the test at Airbus.  The difference between the two wing tests besides the level of maturity of our measurement system, is that no damage should be detected in the wing at Airbus whereas there will be detectable damage in the wing section in EMPA.  So, a positive result will be a success at EMPA but a negative result, i.e. no damage detected, will be a success at Airbus.

The DIMES project has received funding from the Clean Sky 2 Joint Undertaking under the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 820951.

 

The opinions expressed in this blog post reflect only the author’s view and the Clean Sky 2 Joint Undertaking is not responsible for any use that may be made of the information it contains.