Focused rays scattered by an ellipsoidal particle (left). Optical torque along y calculated in the x-y plane using ray scattering with a grid of 400 rays (up, right) and using a trained neural network with the same number of rays (down, right). (Image by the Authors of the manuscript.)Faster and more accurate geometrical-optics optical force calculation using neural networks
David Bronte Ciriza, Alessandro Magazzù, Agnese Callegari, Gunther Barbosa, Antonio A. R. Neves, Maria A. Iatì, Giovanni Volpe, Onofrio M. Maragò
arXiv: 2209.04032
Optical forces are often calculated by discretizing the trapping light beam into a set of rays and using geometrical optics to compute the exchange of momentum. However, the number of rays sets a trade-off between calculation speed and accuracy. Here, we show that using neural networks permits one to overcome this limitation, obtaining not only faster but also more accurate simulations. We demonstrate this using an optically trapped spherical particle for which we obtain an analytical solution to use as ground truth. Then, we take advantage of the acceleration provided by neural networks to study the dynamics of an ellipsoidal particle in a double trap, which would be computationally impossible otherwise.
David presenting at Complex Nanophotonics Science Camp. (Photo by Jacopo Bertolotti) Between the 2nd and the 5th of August David participated in the Complex Nanophotonics Science Camp in Windsor, UK. The Science Camp brought together 60 early-career scientists in the field of photonics but also science writers and editors in an unconventional format – mixing contributed and invited talks, seminars and debates – to present and discuss the latest research and future directions of the field in an open atmosphere and help developing the Complex Nanophotonics community. During this conference David presented a talk on “Elongated active particles in speckle fields“, the questions were many and the community was very interested in the topic. In the journey to Windsor, David visited Phil and Giorgio’s lab, which was a great opportunity to discuss with the other students in the groups.
David and Onofrio during the poster session at MoLE conference in Donostia-San Sebastián. (Photos provided by D. Bronte Ciriza) Between the 25th and the 29th of July 2022 David participated in the MoLE conference in Donostia-San Sebastián. The unexpected demise of Professor Juan José Sáenz, on March 22, 2020, has left his beloved family and friends in shock all over the globe. Following his spirit, MoLE conference 2022 was devoted to honouring his memory the way he would have liked: Appreciated colleagues and friends presenting and discussing their most recent advances, in both electronics and photonics. During this conference David presented a poster on “Elongated active particles in speckle fields“, where he had the chance to discuss the topic with a broad community of interested scientists.
David during the poster session at Cetraro. (Photos provided by D. Bronte Ciriza) During the conference NanoPlasm 2022, David was awarded the best Poster Prize, sponsored by Nanophotonics Journal – De Gruyter. The poster session was full of interesting discussions and ideas with curious researchers. After the official poster sesion we organized a small presentation taking advantage of the beautiful location. Is the future of poster presentations in locations like this?
Spontaneous, self-organized poster session at the beach. (Photos provided by D. Bronte Ciriza)
David during his elevator pitch talk at NanoPlasm 2022. (Photos provided by D. Bronte Ciriza) Between the 13th and the 17th of June David participated in NanoPlasm 2022, which took place in Cetraro, Calabria, Italy. The conference was focused on the rapidly growing fields of Plasmonics and Nano-Photonics, which are opening new frontiers in nanoscience and advanced technologies via novel cross-disciplinary research activities. During this conference David presented 2 posters (titles: “Machine learning enhanced calculations of optical forces in the geometrical optics approximation” and “Elongated active particles in speckle fields“) and an elevator pitch talk, introducing his work on machine learning for optical forces calculations and his recent work on elongated active particles in speckle fields.
David and Fabio with the poster presenting the activities of the Messina chapter. (Photos provided by D. Bronte Ciriza) Between the 2nd and the 4th of June, David was invited to the YM Leadership meeting in Paris to present the outreach activities carried out by the student chapter in Messina. After three years of virtual engagement the meeting brought together almost 50 YM delegates from 20 different countries as well as many interested students and young researchers from outside of the YM network, making it a great success.
Beyond the programme of the LM the co-location with the EPS Forum, allowed the participants to learn about industrial opportunities and to attend lectures from world-class researchers, including 3 Nobel Laureates. Scientific outreach, cultural exchange, and peaceful international collaboration are more important than ever. Bringing young scientists together and equipping them with tools and skills is a great way of fostering these aspects.
Snapshot of the motion of an ellipsoid in a double beam optical trap. (Image by D. Bronte Ciriza) Optical systems are ubiquitous in modern society, with an ever-increasing number of applications covering medical sciences, spatial exploration, information processing and industry, to name but a few examples. In this context, David presented his work on machine learning enhanced optical forces calculations at PHOTOPTICS 2022 between the 10th and the 11th of February. The conference took place online and it was the perfect opportunity to learn from other scientists and discuss the relevance of optics for the study of active matter systems.
David (right) discussing the results with Phil Jones (left). (Photos provided by D. Bronte Ciriza) Between the 11th of the January and the 14th of April David visited UCL to work together with Giorgio Volpe and Phil Jones. During this time in London he studied elongated active particles in complex optical fields, finding some interesting properties that still need to be further understood. Getting to know other people working with soft and active matter gave rise to new ideas and inspiration. More to come!
Carolina (left) and David (right) in the micro 3D printing room. (Image by D. Bronte Ciriza.)From the 11th to the 19th of December 2021, David Bronte Ciriza visited the Soft Materials and Interfaces lab at ETH Zurich. During this visit, David learnt different techniques to fabricate elongated microparticles, and together with Carolina van Baalen produced the ones that will be tested under different optical landscapes in David’s secondment in UCL London. This visit has also served as an opportunity to meet other early stage researchers at ETH Zurich working in related topics, allowing to discuss different ideas in the fields of microfabrication, optical tweezers, and active matter.
Raman Tweezers are used to detect tires and road wear particles in water. We analyze samples collected from a brake test platform, highlighting the presence of car tires and brake particles debris with sub-micrometric dimensions. (Featuring work from Dr Pietro G. Gucciardi, Prof Giovanni Volpe, and Dr Fabienne Lagarde).Raman tweezers for tire and road wear micro- and nanoparticles analysis
R. Gillibert, A. Magazzù, A. Callegari, D. Bronte-Ciriza, A. Foti, M. G. Donato, O. M. Maragò, G. Volpe, M. L. de La Chapelle, F. Lagarde and P. G. Gucciardi.
Tire and road wear particles (TRWP) are non-exhaust particulate matter generated by road transport means during the mechanical abrasion of tires, brakes and roads. TRWP accumulate on the roadsides and are transported into the aquatic ecosystem during stormwater runoffs. Due to their size (sub-millimetric) and rubber content (elastomers), TRWP are considered microplastics (MPs). While the amount of the MPs polluting the water ecosystem with sizes from ∼5 μm to more than 100 μm is known, the fraction of smaller particles is unknown due to the technological gap in the detection and analysis of <5 μm MPs. Here we show that Raman tweezers, a combination of optical tweezers and Raman spectroscopy, can be used to trap and chemically analyze individual TRWPs in a liquid environment, down to the sub-micrometric scale. Using tire particles mechanically grinded from aged car tires in water solutions, we show that it is possible to optically trap individual sub-micron particles, in a so-called 2D trapping configuration, and acquire their Raman spectrum in few tens of seconds. The analysis is then extended to samples collected from a brake test platform, where we highlight the presence of sub-micrometric agglomerates of rubber and brake debris, thanks to the presence of additional spectral features other than carbon. Our results show the potential of Raman tweezers in environmental pollution analysis and highlight the formation of nanosized TRWP during wear.
