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Complex plasma with active Janus particles

Nosenko, Volodymyr (2023) Complex plasma with active Janus particles. Plasma Tech 2023, 26-28 April 2023, Lisbon, Portugal. (Unpublished)

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A two-dimensional complex plasma containing active Janus particles was studied experimentally. A single layer of micrometer-sized plastic microspheres was suspended in the plasma sheath of a radio-frequency (rf) discharge in argon at low pressure. The particle sample used was a mixture of regular particles and Janus particles, which were coated on one side with a thin layer of platinum. The experiments were carried out in a modified Gaseous Electronics Conference (GEC) rf reference cell. Plasma was produced by a capacitively coupled rf discharge in argon at 13.56 MHz. The gas pressure was 1.66 Pa, the discharge rf power was 20 W. As expected, the regular melamine-formaldehyde (MF) particles formed a two-dimensional triangular lattice (plasma crystal) in our experimental conditions. The lattice consisted of ≈ 1900 particles and was highly ordered, as evidenced by the pair correlation function for particles g(r) with the high first and split second peaks. On the contrary, the suspension of the mixed Janus particles did not crystallize. Instead, the particles energetically moved around colliding with each other. The pair correlation function for the mixed Janus particles g(r) indicates a highly disordered (gas-like) state. The mean-squared displacement MSD(t) of the mixed Janus particles scales as MSD(t) ∝ t^α with α = 2 at small times t ≪ γ^−1, where γ is the neutral-gas damping rate for the particles, indicating ballistic motion. Here, the particle inertia is important. At later times, the dynamical exponent α(t) declines, finally reaching the value of ≈ 0.56. We ascribe this to the combined effect of the Janus particle propensity to move in circular trajectories due to a combination of the photophoretic force from the illumination laser and the oppositely directed ion drag force and external confinement.

Item URL in elib:https://elib.dlr.de/195509/
Document Type:Conference or Workshop Item (Speech)
Title:Complex plasma with active Janus particles
AuthorsInstitution or Email of AuthorsAuthor's ORCID iDORCID Put Code
Date:27 April 2023
Refereed publication:No
Open Access:No
Gold Open Access:No
In ISI Web of Science:No
Keywords:complex plasma, active matter, Janus particles, plasma coating
Event Title:Plasma Tech 2023
Event Location:Lisbon, Portugal
Event Type:international Conference
Event Dates:26-28 April 2023
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Space
HGF - Program Themes:Research under Space Conditions
DLR - Research area:Raumfahrt
DLR - Program:R FR - Research under Space Conditions
DLR - Research theme (Project):R - Model systems
Location: Köln-Porz
Institutes and Institutions:Institute of Materials Physics in Space > Scientific Experiments MP
Deposited By: Nosenko, Volodymyr
Deposited On:19 Jun 2023 06:45
Last Modified:19 Jun 2023 06:45

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