Tag Archives: mechanics

Mapping the road between digital twins and NDE

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RoadmapMichael Grieves, who probably first formulated the concept of digital twins in 2002, stated that all information about a physical entity should be present in its cyber or digital twin with data flow from the physical entity to the digital twin, and information flow from the digital twin to the physical entity throughout its lifecycle [1] [see ‘Digital twins that thrive in the real-world’ on June 9th, 2021].  The realisation of data flows between cyber-physical twins has been slow and there are relatively few cases where this definition has been fully implemented.  Non-destructive evaluation (NDE) is a well-established set of techniques used to assess the properties, integrity and condition of engineering components and structures that could play a significant role in supplying data to digital twins.  At the moment NDE is commonly used in quality control to check for manufacturing defects, in integrity assessments to investigate damage in safety critical components during maintenance inspections, and for determining the remaining life expectancy of engineering parts.  The integration of NDE in digital engineering has been slow; so, in a recent study, involving representatives from a wide range of industries, we have defined in a roadmap [2] the potential opportunity and the route to its realisation.  This work represents a different approach to research for my group in that we have explored the need or the ‘pull’ from industry rather than delivering innovative technology which can result in a ‘push’ to industry [see for example, ‘Our last DIMES’ on September 22nd, 2021].  My regular readers might also detect the influence of social science, which also surfaced in our recent work on knowledge management [see ‘Opportunities lost in knowledge management using digital technology’ on October 25th, 2023 and ‘Evolutionary model of knowledge management’ on March 6th 2024].  We have used the same methods, based on semi-structured interviews and thematic analysis, across all of these studies.

Image: roadmap [© University of Liverpool] which should be read in conjunction with [2].

References:

  1. Grieves, M., Vickers, J. (2017). Digital Twin: Mitigating Unpredictable, Undesirable Emergent Behavior in Complex Systems. In: Kahlen, J., Flumerfelt, S., Alves, A. (eds) Transdisciplinary Perspectives on Complex Systems. Springer, Cham.
  2. Middleton CA, Nguyen T & Patterson EA, NDE4.0 and digital twins in industry: current user experiences and future development, J. Nondestructive Evaluation, 45:107, 2026.

Real-time label-free tracking of bacteriophages interacting with bacteria

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(a) Two-dimensional random dynamics (blue line) of a pelp20 bacteriophage monitored for a period of 5 s. Scale bar, 2 µm. (b) A plot of the same dynamics and (c) the mean square displacement (MSD) of the random walk. The MSD of the random walk is represented by square data points, and a linear fit (black line) has been applied to the data.

(a) Two-dimensional random dynamics (blue line) of a pelp20 bacteriophage monitored for a period of 5 s. Scale bar, 2 µm. (b) A plot of the same dynamics and (c) the mean square displacement (MSD) of the random walk. The MSD of the random walk is represented by square data points, and a linear fit (black line) has been applied to the data (Figure 4 from https://royalsocietypublishing.org/view-large/figure/20098614/rsif.2026.0250.f004.tif)

I was excited last month when our latest research on tracking nano-entities was published by the Journal of the Royal Society Interface.  The paper describes the real-time and label-free tracking of bacteriophages, or phages, in an optical microscope using caustics (see right thumbnail).  Phages are of interest due to the potential applications in biotechnology and medicine.  They selectively infect and replicate within bacteria and play an important role in regulating bacterial populations across many ecosystems.  I have written previously about the threat of antimicrobial resistant (AMR) infections and our research on the real-time tracking of individual bacterium that could be responsible for such infections [see ‘Label-free real-time tracking of individual bacterium‘ on January 25th, 2023].  In this newly published paper, we describe tracking phages as they interact with and compromise bacteria (see bottom thumbnail) using the same technique, optical caustics [see ‘Caustics‘ on October 15th, 2024 and application to ‘Nanoparticle motion through heterogeneous hydrogels‘ on November 6th, 2024 and to ‘Corona-induced transition from molecular to particle motion in biological media‘ on December 4th, 2024]. Traditionally, phages have been monitored using fluorescent labelling because their size is nanometric which renders them invisible in a conventional optical microscope.  However, chemically attaching labels to nano entities has been shown to influence their dynamics.  Hence, this new study represents a significant advance that will accelerate the real-time observation of phage-bacteria interactions which will enable the development of phage-based diagnostics and antimicrobial therapies.

Sources:

Francesco Giorgi, Samuel Chenery, Liberty Duignan, Joanne L. Fothergill, Eann Patterson, Judith M. Curran; Elucidating bacteriophage dynamics and interactions with real-time label-free optical imaging. J R Soc Interface 1 May 2026; 23 (238): 20260250. https://doi.org/10.1098/rsif.2026.0250

Details of E. coli bacteria: (a) not exposed (reprinted from [17]) and (b,c) exposed to a population of EcoLiv25 phages in solution. In (b), the arrow points at the supposed presence of a phage attached to the bacterium’s external membrane, while in (c), the arrows point at the compromised sections of the bacterium’s external membrane as a result of phage infection. Scale bars, 2 µm.

Details of E. coli bacteria: (a) not exposed and (b,c) exposed to a population of EcoLiv25 phages in solution. In (b), the arrow points at the supposed presence of a phage attached to the bacterium’s external membrane, while in (c), the arrows point at the compromised sections of the bacterium’s external membrane as a result of phage infection. Scale bars, 2 µm (Figure 6 from https://royalsocietypublishing.org/view-large/figure/20098622/rsif.2026.0250.f006.tif).

Star sequence minimises distortion

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It is some months since I have written about engineering so this post is focussed on some mechanical engineering.  The advent of pneumatic and electric torque wrenches has made it impossible for the ordinary motorist to change a wheel because it is very difficult to loosen wheel nuts by hand when they have been tightened by a powered wrench which most of us do not have available.  This has probably made motoring safer but also means we are more likely to need assistance when we have a flat tire.  It also means that the correct tightening pattern for nuts and bolts is less widely known.  A star-shaped sequence is optimum, i.e., if you have six bolts numbered sequentially around a circle then you start with #1, move across the diameter to #4, then to #2 followed by #5 across the diameter, then to #3 and across the diameter to #6.  This sequence is optimum for flanges, bolted joints in the frames of buildings and joining machine parts as well as wheel nuts.  We have recently discovered that it works in reverse, in the sense that it is the optimum sequence for releasing parts made by additive manufacturing (AM) from the baseplate of the AM machine (see ‘If you don’t succeed try and try again’ on September 29th, 2021).  Additive manufacturing induces large residual stresses as a consequence of the cycles of heat input to the part during manufacturing and some of these stresses are released when it is removed from the baseplate of the AM machine, which causes distortion of the part.  Together with a number of collaborators, I have been researching the most effective method of building thin flat plates using additive manufacturing (see ‘On flatness and roughness’ on January 19th, 2022).  We have found that building the plate vertically layer-by-layer works well when the plate is supported by buttresses on its edges.  We have used two in-plane buttresses and four out-of-plane buttresses, as shown in the photograph, to achieve parts that have comparable flatness to those made using traditional methods.  It turns out that optimum order for the removal of the buttresses is the same star sequence used for tightening bolts and it substantially reduces distortion of the plate compared to some other sequences.  Perhaps in retrospect, we should not be surprised by this result; however, hindsight is a wonderful thing.

The current research is funded jointly by the National Science Foundation (NSF) in the USA and the Engineering and Physical Sciences Research Council (EPSRC) in the UK and the project was described in ‘Slow start to an exciting new project on thermoacoustic response of AM metals’ on September 9th 2020.

Image: Photograph of a geometrically-reinforced thin plate (230 x 130 x 1.2 mm) built vertically layer-by-layer using the laser powder bed fusion process on a baseplate (shown removed from the AM machine) with the supporting buttresses in place.

Sources:

Patterson EA, Lambros J, Magana-Carranza R, Sutcliffe CJ. Residual stress effects during additive manufacturing of reinforced thin nickel–chromium plates. IJ Advanced Manufacturing Technology;123(5):1845-57, 2022.

Khanbolouki P, Magana-Carranza R, Sutcliffe C, Patterson E, Lambros J. In situ measurements and simulation of residual stresses and deformations in additively manufactured thin plates. IJ Advanced Manufacturing Technology; 132(7):4055-68, 2024.

Corona-induced transition from molecular to particle motion in biological media

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Light signatures generated by particles in a nanoscopeIn last month’s post [see ‘Nanoparticle motion through heterogeneous hydrogels’ on November 6th, 2024], I described our recent work on tracking nanoparticles through a model of the vitreous humour and mentioned it was the first of two articles published in the Nature journal, Scientific Reports.  In the second article, we explored the use of caustics in an optical microscope [see ‘Seeing the invisible’ on October 29th, 2014] to track nanoparticles in biofluids.  Nanoparticles are below the resolution of an optical microscope because they are substantially smaller than the wavelength of visible light; hence, they are usually tracked using fluorescent markers or tags attached chemically to the nanoparticles.  These tags can influence both the motion of the particles and biological activity so caustics provide a label-free technique that allows particles to be tracked in real-time using a standard optical microscope.  In most of our previous research, we have tracked nanoparticles in transparent fluids such as water, glycerol-water mixtures, or the hydrogels described in last month’s post.  In our latest work, we have tracked small nanoparticles with diameters from 10 to 100 nm in common cell culture media with different concentrations of serum proteins.  These fluids are a ‘soup’ of complex protein molecules that interact with one another and the gold nanoparticles being tracked.  We found that the presence of proteins caused a reduction in the rate of diffusion for both positively- and negatively-charged particles and we concluded that the proteins form a corona around each nanoparticle effectively enlarging its diameter.  For larger nanoparticles, and those positively-charged, the enlargement appears to cause a transition from molecular motion, in which particle diameter is unimportant, to particle motion where larger particles diffuse more slowly.  We first explored this transition from fractional to classical Stokes-Einstein behaviour in simple fluids in 2017 [‘Slow moving nanoparticles‘ on December 13th 2017] and it seems likely to be complicated in these complex fluids.  Hence, understanding protein dynamics as well nanoparticle dynamics will be essential to the development of nanotechnologies applicable in biological environments.  So, we have lots more work to do!

Sources:

Schleyer G, Patterson EA, Curran JM. Label free tracking to quantify nanoparticle diffusion through biological media. Scientific Reports. 2024 Aug 13;14(1):18822.

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.