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Laser-induced heating for the experimental study of critical Casimir forces with optical trapping
by Ignacio A. Martinez, Artyom Petrosyan, Sergio Ciliberto
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Submission summary
| Authors (as registered SciPost users): | Ignacio A. Martinez |
| Submission information | |
|---|---|
| Preprint Link: | https://arxiv.org/abs/2309.06773v1 (pdf) |
| Date submitted: | 2023-09-19 09:53 |
| Submitted by: | Martinez, Ignacio A. |
| Submitted to: | SciPost Physics |
| Ontological classification | |
|---|---|
| Academic field: | Physics |
| Specialties: |
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| Approach: | Experimental |
Abstract
Critical Casimir interactions represent a perfect example of bath-induced forces at mesoscales. These forces may have a relevant role in the living systems as well as a role in the design of nanomachines fueled by environmental fluctuations. Since the thermal fluctuations are enhanced in the vicinity of a demixing point of a second-order phase transition, we can modulate the magnitude and range of these Casimir-like forces by slight changes in the temperature. Here, we consider two optical trapped colloidal beads inside a binary mixture. The Casimir interaction is controlled by warming the mixture by laser-induced heating, whose local application ensures high reproducibility. Once this two-particle system is warmed, the critical behavior of different observables allows the system to become its self-thermometer. We use this experimental scheme for analyzing the energetics of a critical colloidal system under a non-equilibrium-driven protocol. We quantify how the injected work can be dissipated to the environment as heat or stored as free energy. Indeed, our system allows us to use the fluctuation theorems framework for analyzing the performance of this critically driven toy model. Our work paves the way for future experimental studies on the non-equilibrium features of bath-induced forces and the design of critically driven nanosystems.
Current status:
Reports on this Submission
Report #2 by Anonymous (Referee 2) on 2023-10-24 (Invited Report)
- Cite as: Anonymous, Report on arXiv:2309.06773v1, delivered 2023-10-24, doi: 10.21468/SciPost.Report.7990
Strengths
Original new idea pointing towards the realization of novel types of nanomachines.
Report
This study reports on a two-particle systems whose interaction are modulated via critical Casimir forces which can be tuned by minute changes in the temperature. By applying a protocol where the displacement of particles is synchronized with their Casimir-induced attraction, this leads to a toy machine where work can be extracted.
This is an original and well-written paper which certainly deserves publication in SciPost after the authors have addressed the following questions:
1. Variations of the temperature will also change the order parameter profile around the particle. Due to the difference in dielectric properties of the two phases (which is exploited by the authors for the measurement of temperature) this may also influence the optical trapping. Can the authors comment on that?
2. Did the authors also consider vertical changes in the particle position during their protocol?
3. It would be helpful, the authors could discuss the differences between their engine and a colloidal Carnot or Stirling engine. My impression is, that apart from the technical realization, there are large similarities. In both cases the available phase volume of the colloid is periodically changed which leads to the extraction of work.
Requested changes
1. Variations of the temperature will also change the order parameter profile around the particle. Due to the difference in dielectric properties of the two phases (which is exploited by the authors for the measurement of temperature) this may also influence the optical trapping. Can the authors comment on that?
2. Did the authors also consider vertical changes in the particle position during their protocol?
3. It would be helpful, the authors could discuss the differences between their engine and a colloidal Carnot or Stirling engine. My impression is, that apart from the technical realization, there are large similarities. In both cases the available phase volume of the colloid is periodically changed which leads to the extraction of work.
Strengths
This paper reports a novel experimental setup for measuring and controlling the
force between two colloidal particles using a laser trap. By gradually modulating the intensity of the
laser beam, the authors can measure and alter the forces acting
on two beads, and at the same time monitoring the amount of heating induced by the laser. This is an important improvement from the prior experiments where the heat generation by the trapping laser was often ignored. This improved approach will allow more precise force measurements using optical tweezers.
Weaknesses
None.
Report
The paper is well written and I recommend publication in the present form.
Requested changes
none