Iron Nanochains

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Caustics formed from iron nanoparticles coalescing into chains aligned with the lines of the magnetic field from an adjacent magnet

Many people will be familiar with an iron filings and magnet experiment often performed in high school physics classes.  Iron filings on a sheet of paper with a magnet underneath, when the paper is gently tapped, align with the lines of the magnetic field sometimes forming ‘chains’.  In our research group, we have performed a version of this experiment at the nanoscale using iron nanoparticles smaller than 200nm in diameter floating in deionised water on a microscope slide.  We brought a magnet into close proximity with the slide and the nanoparticles formed chains aligned along the lines of magnetic field which we visualised using caustics [see ‘Holes in fluids’ on October 22, 2014].  When we removed the magnet, the nanoparticles resumed their Brownian motion.  Not a ground-breaking experiment but it’s exciting to be able to demonstrate that the phenomenon occurs at the nanoscale and that we can observe it.

Worldly goods and routes to happiness

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Decorative image of a flowerIn her novel, ‘The Gap of Time’, Jeanette Winterson writes that Buddha and Jesus knew that when you had so much money that you could buy anything, everything, then worldly goods were worthless.  Modern capitalism has generated a small number of owners of capital who have this much money.  For the rest of us worldly goods are not valueless or worthless.  Omnipresent advertising tends to create a desire in many of us for a lifestyle that is unattainable with our income, which can lead us to be dissatisfied and unhappy.  Some surveys have suggested that engineers are amongst the happiest people [see ‘Choosing a career is like going shopping’ on June 17th, 2015].  Perhaps this is because we managed to do as Rutger Berger suggested in his 2025 BBC Reith Lecture, which is to measure our success in terms of our contribution to tackling humanity’s toughest problems.  For many engineers, this is a key component of their role.

Sources

Jeanette Winterson, The Gap of Time, Penguin, London 2015

Simon van Teutem, How our brightest minds get trapped in the city, FT 18/19 October 2025.

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).

Beyond language with stochastic parrots

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Decorative image of a summer flowerSome months ago, I wrote in unflattering terms about artificial intelligence applications (AI apps) and large language models (LLMs), (see ‘Ancient models and stochastic parrots‘ on October 1st, 2025).  My view is changing, probably as AI apps develop and my user skills improve.  I have started using a couple of different free AI apps as research assistants in three ways.  First, when I am writing administrative documents, such as a job description for a Coordinator of AI in Education, for which a job title was sufficient for the app to generate a first draft that only required light editing and tailoring to the specific context.  Second, using a different AI app, to answer questions about phenomena which have allowed me to construct explanations for observations made of new and, or, complex systems – I could have delved into textbooks and monographs or searched research articles but AI does this much more quickly.  The third way I have used AI apps is to identify gaps in knowledge that could be fruitful topics for research.  This is a more difficult task because AI apps only know about stuff they can find on the internet in the form of language or text.  Hence, I have to ask questions with answers that reveal something unknown or not understood.  This is not straightforward because LLMs are fundamentally constrained by language.  In ‘The Years’, Annie Ernaux wrote that ‘language will continue to put the world into words’.  Yann LeCun, Meta’s former chief scientist, has suggested that to understand how the world works, a model would need to learn from videos and spatial data, not just language, and that without this type of learning human-level intelligence is impossible.  He has set up a new company, Advanced Machine Intelligence Labs, to do just that.  Language is used by people to describe the world from their perspective which might be inaccurate, incomplete or distorted and that can mislead LLMs.  However, using AI apps we can also ‘distort’ videos of the world, so that machine intelligence will have to be based on direct observation of the real-world, which after all is the approach that science attempts to use.

Source:

Yann LeCun, Intelligence is really about learning. FT Weekend, 3-4 January 2026

Annie Ernaux, The Years, Fitzcarraldo Editions, London, 2018.