Non-equilibrium Properties of an Active Nanoparticle in a Harmonic Potential
Falko Schmidt, Hana Šípovà-Jungová, Mikael Käll, Alois Würger & Giovanni Volpe
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 and other researchers at the University of Gothenburg, in collaboration with Business students at the Chalmers School of Entrepreneurship, have received early acclaimfor their Start-up idea “Lucero Bio”.
Lucero Bio was ranked among one of the top 5 business ideas in West Sweden by Venture Cup Sweden. Out of the 376 ideas that were submitted to the competition, nearly half came from the western region of Sweden.
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.
Team components: Christopher Jacklin, Rich Zapata Rosas, Felix Mossberg, Falko Schmidt, Alejandro Diaz Tormo and Martin Mojica-Benavides.
On Friday, the 13th of December, Falko Schmidt, will visit Juliane Simmchen’s lab at the Technical University of Dresden. He will present results on Liquid-Liquid-Phase Separation a project that is currently in collaboration with their lab.
Light-induced phase separation power novel micro machines Falko Schmidt, and Giovanni Volpe
Light at the Nanoscale Conference, Chalmers University, Gothenburg, Sweden
5 December 2019, 16:30-18:30
Phase separation is a phenomena that commonly exists in nature, from the freezing of ice to the intrinsic mechanism of the cell to order matter. We are exploiting phase separations to produce new types of miniaturised machines, in particular micron and nano sized engines1as well as to form self-assembled colloidal molecules2. We control their behaviour using only light and varying its ambient temperature making this a simple tool to study complex matter3. This will enhance the development of future medicine where nano robots deliver drugs specifically to the local infection side.
References:1. F. Schmidt et al. Microscopic engine powered by critical demixing, Phys Rev Lett 120, 068004, 2018
2. F. Schmidt et al. Light-controlled assembly of active colloidal molecules, J Chem Phys150, 094905, 2019
3. S. Bo et al. Measurement of anomalous diffusion using recurrent neural networks, Phys Rev E 100, 010102(R), 2019
Falko Schmidt, and Jalpa Soni have been selected to attain the 69th Lindau Nobel Laureate meeting in Lindau, Germany from the 30th June till 5th July 2019.
The Lindau meeting is a platform where 600 young scientists around the world meet former Nobel laureates (as well as Turing-award winners). There they can exchange scientific ideas and experiences, inspire each other and connect for a more interdisciplinary scientific community. These are the three incentives that make this meeting a unique experience.
Falko Schmidt had the privilege to attend it and shares the following insight:
“For me, the Lindau meeting was a unique experience where I was able to meet peers across many disciplines, share ideas and experiences beyond my field of active matter and received much feedback on career choices and daily life as a PhD. Especially fruitful were the many possibilities to engage with senior scientists such as the Nobel laureates which with their humour, insight and advice deepened my passion about science. Personally, I would consider my best encounters with Steven Chu and William Phillips (Nobel Prize in Physics in 1997 on laser cooling), Donna Strickland (Nobel Prize in Physics in 2018 on ultra-fast lasers), and Stefan Hell (Nobel Prize in Chemistry in 2014 on super-resolution microscopy). I am very grateful for the possibility of attending this meeting and would like to thank the Lindau Nobel committee and Söderbergs Foundation who were selecting and sponsoring me.
From now on, in times of struggle, I will always look back to this meeting and remember why we all love doing science.”
About mid-way through his PhD, Falko Schmidt presented his past research activities and gave an outlook on his future projects. The topics range from miniaturised machines to self-assembled active molecules activated by light to machine-learning techniques to better characterise dynamical behaviour of microscopic systems.
The seminar will be held at the Department of Physics at Gothenburg University, June 10th 2019 starting at 12:15 p.m.
Light-driven Assembly and Optical Manipulation of Active Colloidal Molecules
Falko Schmidt, Benno Liebchen, Hartmut Loewen & Giovanni Volpe
OSA Biophotonics Congress, Tucson (AZ), USA
16 April 2019
Active matter, consisting of self-propelled units locally injecting energy into the system, opens new horizons for the creation of functional soft materials with designable properties. Experiencing a constant energy input, allows active matter to self-assemble into phases with a complex architecture and functionality such as living clusters which dynamically form, reshape and break-up but would be forbidden in equilibrium material by the entropy maximization (or free energy minimization) principle. The challenge to control this active self-assembly has evoked widespread efforts typically hinging on an engineering of the properties of individual motile constituents. Here, we provide a different route, where activity occurs as an emergent phenomenon only when individual building blocks bind together, in a way which we control by laser light. Using experiments and simulations of two species of immotile microspheres, we exemplify this route by creating active molecules featuring a complex array of behaviors, becoming migrators, spinners and rotators. The possibility to control the dynamics of active self-assembly via light-controllable nonreciprocal interactions will inspire new approaches to understand living matter and to design active materials.
The first symposium on the topic of Nanophotonics brings together researchers from physics and chemistry departments in Gothenburg to present their work and share ideas.
Organised by Dr. R. Verre from the Bionanophotonic group at Chalmers University of Technology seven different groups will be present among which F. Schmidt will represent our Softmatter division of Gothenburg University.
The symposium will take place on the 26th of March 2019 at Kollektorn in MC2, Chalmers Campus. Everybody is welcome to attend!
Jalpa Soni and Falko Schmidt have been nominated by the Marie-Curie association and the Ragnar-Söderbergs foundation to attend the 69th Lindau Nobel Laureate Meeting from the 30 June till 5 July 2019. Congratulations to both!
The Lindau Nobel Laureate Meeting is an annual scientific conference that brings together Nobel laureates and young scientists to encourage scientific exchange among different generations and cultures.
The 69th meeting will be dedicated to Physics, where 580 young scientist from 88 countries will be present.