Falko Schmidt, Hana Sipova-Jungova, Mikael Käll, Alois Würger, Giovanni Volpe
Submitted as OSA-OMA-2021, AF1D.2 Contribution
Date: 16 April
Time: 12:30 CEST
Short Abstract
We investigate a nanoparticle inside an optical trap and driven away from equilibrium by self-induced concentration gradients. We find that a nanoparticle performs fast orbital rotations and its probability density shifting away from equilibrium.
Non-equilibrium properties of an active nanoparticle in a harmonic potential
Falko Schmidt, Hana Šípová-Jungová, Mikael Käll, Alois Würger & Giovanni Volpe
Nature Communications 12, 1902 (2021)
doi: 10.1038/s41467-021-22187-z
arXiv: 2009.08393
Active particles break out of thermodynamic equilibrium thanks to their directed motion, which leads to complex and interesting behaviors in the presence of confining potentials. When dealing with active nanoparticles, however, the overwhelming presence of rotational diffusion hinders directed motion, leading to an increase of their effective temperature, but otherwise masking the effects of self-propulsion. Here, we demonstrate an experimental system where an active nanoparticle immersed in a critical solution and held in an optical harmonic potential features far-from-equilibrium behavior beyond an increase of its effective temperature. When increasing the laser power, we observe a cross-over from a Boltzmann distribution to a non-equilibrium state, where the particle performs fast orbital rotations about the beam axis. These findings are rationalized by solving the Fokker-Planck equation for the particle’s position and orientation in terms of a moment expansion. The proposed self-propulsion mechanism results from the particle’s non-sphericity and the lower critical point of the solute.
Falko Schmidt, Agnese Callegari, Giovanni Volpe
(online at) MPI Stuttgart, Germany
11 February 2021, 14:30-16.00
We propose a mechanism for restoration of collapsed structures using critical Casimir forces by investigating the diffusion of metal flake-like particles. By tuning temperature near-criticality and employing selective self-assembled monolayers the resulting repulsive critical Casimir force is large enough to lift off particle and enable transitions previously impeded by QED Casimir attraction.
Falko Schmidt defended his PhD Thesis in Physics on Friday, 15 January 2021. Congrats!
The disputation took place at 9 a.m., in PJ salen, Fysikgården.
Falko Schmidt’s opponent, Peer Fischer, gave an introductory presentation with title “Microswimmers and motile active matter”.
Link: http://hdl.handle.net/2077/66807
The motion of microscopic objects is strongly affected by their surrounding environment. In quiescent liquids, motion is reduced to random fluctuations known as Brownian motion. Nevertheless, microorganisms have been able to develop mechanisms to generate active motion. This has inspired researchers to understand and artificially replicate active motion. Now, the field of active matter has developed into a multi-disciplinary field, with researchers developing artificial microswimmers, producing miniaturized versions of heat engines and showing that individual colloids self-assemble into larger microstructures. This thesis taps into the development of artificial microscopic and nanoscopic systems and demonstrates that passive building blocks such as colloids are transformed into active molecules, engines and active droplets that display a rich set of motions. This is achieved by combining optical manipulation with a phase-separating environment consisting of a critical binary mixture. I first show how simple absorbing particles are transformed into fast rotating microengines using optical tweezers, and how this principle can be scaled down to nanoscopic particles. Transitioning then from single particles to self-assembled modular swimmers, such colloidal molecules exhibit diverse behaviour such as propulsion, orbital rotation and spinning, and whose formation process I can control with periodic illumination. To characterize the molecules dynamics better, I introduce a machine-learning algorithm to determine the anomalous exponent of trajectories and to identify changes in a trajectory’s behaviour. Towards understanding the behaviour of larger microstructures, I then investigate the interaction of colloidal molecules with their phase-separating environment and observe a two-fold coupling between the induced liquid droplets and their immersed colloids. With the help of simulations I gain a better physical picture and can further analyse the molecules’ and droplets’ emergence and growth dynamics. At last, I show that fluctuation-induced forces can solve current limitations in microfabrication due to stiction, enabling a further development of the field towards smaller and more stable nanostructures required for nowadays adaptive functional materials. The insights gained from this research mark the path towards a new generation of design principles, e.g., for the construction of flexible micromotors, tunable micromembranes and drug delivery in health care applications.
The spinoff Lucero emerged a year ago as a joint effort between the Soft Matter Lab, the Biological Physics Group and the Chalmers School of Entrepreneurship. The idea of providing a non-invasive micromanipulation platform recently received initial support from the European Research Council (Proof of Concept) and Chalmers Ventures. Lucero has now been nominated for “Best HealthTech Startup” in the Swedish national final of the prestigious Nordic Startup Awards. National winners are partially determined by public vote and will go on to compete against the winners from Iceland, Finland, Norway, and Denmark in the Nordic Final.
The public voting period is now open and the winner of each category will be announced on November 26th.
To vote, click here.
“The first prototype is on its way and we hope to start the initial tests with biological samples pretty soon, all thanks to the support from Chalmers Ventures and Prof. Giovanni Volpe.” Alejandro Diaz, co-founder of Lucero.
Lucero is joined by four other up-and-coming Swedish startups in the HealthTech category, including Spermosens, tendo, Flow Neuroscience, and Deversify.
Other categories include: Startup of the Year, Best Newcomer, Founder of the Year, Investor of the Year, Best Co-working Space, Best Accelerator/Incubator Program, Ecosystem Hero of the Year, Best Virtual Teamwork Solution, People’s Choice, and Best Climate Impact Startup.
The Nordic Startup Awards is part of the Global Startup Awards, which is a large startup competition that aims to recognize and connect entrepreneurs, investors, accelerator/incubator programs, and government initiatives from all around the world.
Follow Lucero’s updates on Lucerobio.com/, LinkedIn, and Instagram.
Links:
LinkedIn: https://www.linkedin.com/company/lucero/
Instagram: https://www.instagram.com/lucero_bio/
Lucerobio: https://www.lucerobio.com/
From basic research to founding a startup company: A personal journey to the unknown
Falko Schmidt
Career Seminar, Online, University of Gothenburg, Sweden
14 October 2020, 11:30-13:00
26 November 2020, 11:30-13:00
I am currently a PhD student at the Physics Department of the University of Gothenburg and will defend at the beginning of 2021. For a couple of years I have been playing with different ideas for a startup already, involving technical solutions developed during my time as PhD and was looking for their applications in the real world. After a couple of failures I have recently founded my own startup company Lucero AB. We will develop automated optical manipulation solutions for single cell analysis with applications in research on longevity, viral diseases and in the pharmaceutical industry. During this seminar I will share my insights on how to find ideas, how to validate them and the process towards creating a startup company.
This seminar is a recurring seminar and it is part of the Career Development and Entrepreneurship series initiated by the Faculty of Science. It will take place during the autumn 2020 and spring 2021.
Please check the links below for the planned dates:
14 October: Career seminars for PhD students at the Dept of Biological and Environmental Sciences and the Dept of Marine Sciences
26 November: Career seminars for PhD students at the Dept of Mathematical Sciences (GU and Chalmers)
Additional dates will be added later.
Dynamics of an active nanoparticle in an optical trap
Falko Schmidt, Hana Šípová-Jungová, Mikael Käll, Alois Würger, Giovanni Volpe
Click here to see the slides.
Twitter Link: here.
Active matter systems in non-equilibrium conditions have recently gained great interest from many disciplines such as micro and nanomachines and in living organisms. Probing the dynamics of active Brownian particles (ABPs) under confinement such as found in biological systems gives insight into their non-equilibrium processes. Although previous studies [1-4] have shown the effect of confinement on ABPs on the microscale and macroscale investigating dynamics on the nanoscale remains challenging where thermal fluctuations typically prevail. Here, we are investigating experimentally and theoretically a nanoscopic particle in the harmonic potential of an optical trap and driven away from equilibrium by self-induced concentration gradients. We find that a nanoparticle performs fast orbital rotation at finite distance from the trap center and its probability density shifts from a Gaussian to a skewed distribution. Furthermore, we show that by transfer of spin angular momentum from the trapping beam the direction of the particle’s rotation can be controlled. We develop a theoretical model of this system which reveals that the driving mechanism of such fast rotation is the particle’s non-sphericity providing insight for the development of future nanoscopic engines.
References
[1] S. C. Takatori et al., Nat. Comm., 7, 10694 (2016)
[2] O. Dauchot & V. Démery, Phys. Rev. Lett., 122, 068002 (2019)
[3] A. Pototsky & H. Stark, EPL, 98, 5004 (2012)
[4] F. Schmidt et al., Phys. Rev. Lett., 120, 068004 (2018)
Poster Session
Time: June 22nd 2020
Place: Twitter
POM Conference
Link: POM
Time: June 25th 2020
Place: Online
Six members of the Soft Matter Lab (Aykut Argun, Falko Schmidt, Laura Pérez-Garcia, Saga Helgadottir, Alessandro Magazzù, Daniel Midtvedt) were selected for poster presentations at the Photonics Online Meet-up (POM).
POM is an entirely free virtual conference. It aims to bring together a community of early career and established researchers from universities, industry, and government working in optics and photonics.
The meeting, at its second edition, will be held on June 25th 2020, 9-14.30 Central European Time. The virtual poster session will take place on June 22nd, on Twitter and virtual reality.
The poster contributions being presented are:
Aykut Argun
Enhanced force-field calibration via machine learning
Twitter Link: here.
Falko Schmidt
Dynamics of an active nanoparticle in an optical trap
Twitter Link: here.
Laura Pérez-García
Optical force field reconstruction using Brownian trajectories
Twitter Link: here.
Saga Helgadottir
DeepTrack: A comprehensive deep learning framework for digital microscopy
Twitter Link: here.
Alessandro Magazzù
Controlling the dynamics of colloidal particles by critical Casimir forces
Twitter Link: here.
Daniel Midtvedt
Holographic characterisation of subwavelength particles enhanced by deep learning
Twitter Link: here.
Our idea Lucero, has reached the semi-final for the SPIE Start-up challenge, where will pitch in front of a jury at Photonics West in San Francisco, CA, USA on the 4th of February 2020.
Lucero will compete, among other 41 semifinalists, for cash prizes and business support.
In addition, Lucero was awarded one of the three Early Stage Entrepreneurship Travel Grants to attend the semi-final.
The start-up is aiming to make cutting-edge laser technology easy to use and available to anyone by combining it with commercial microscope. The product and software combo utilizes optical tweezers in a brand-new way – and bridges the gap between physics and other scientific fields that would greatly benefit from easier access to this tool.
In December, Lucero was ranked among the best 5 business ideas in West Sweden.
Team components: Christopher Jacklin, Rich Zapata Rosas, Felix Mossberg, Falko Schmidt, Alejandro Diaz Tormo and Martin Mojica-Benavides.
Links: Lucero Homepage
On Monday, the 16th of December, Falko Schmidt, will visit Frank Cichos’ lab at the University of Leipzig. He will present latest research on a nanoscopic particle in a harmonic trap.
