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Abstract Liquid–liquid or liquid–air interfaces provide interesting environments to study colloids and are ubiquitous in nature and industry, as well as relevant in applications involving emulsions and foams. They present a particularly intriguing environment for studying active particles that exhibit a host of phenomena not seen in passive systems. Active particles can also provide on‐demand controllability that greatly expands their use in future applications. However, research on active particles at interfaces is relatively rare compared to those at solid surfaces or in the bulk. It is studied magnetically steerable active colloids at a liquid–air interface that self‐propel by bubble production via the catalytic decomposition of chemical fuel in the liquid medium. It is investigated the bubble formation and dynamics of “patchy” colloids with a patch of catalytic coating on their surface and compare to more traditional Janus colloids with a hemispherical coating. It is found that the patchy colloids have a tendency to produce smaller bubbles and undergo smoother motion which makes them beneficial for applications such as precise micro‐manipulation. this it is demonstrated by using them to manipulate and assemble patterns of passive spheres on a substrate as well as at an air–liquid interface. It is also characterized the propulsion and bubble formation of both the Janus and patchy colloids and find that previously proposed theories are insufficient to fully describe their motion and bubble bursting mechanism. Additionally, it is observed that the colloids, which reside at the air–liquid interface, demonstrate novel interfacial positive gravitaxis toward the droplet edges, which it is attributed to a torque resulting from opposing downward and buoyant forces on the colloids.
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Bottom-Up Construction of the Interaction between Janus Particles
While the interaction between two uniformly charged spheres—viz colloids—is well- known, the interaction between non-uniformly charges spheres such as Janus particles is not. Specifically, the Derjaguin approximation relates the potential energy between two spherical particles with the interaction energy Vpl per unit area between two pla- nar surfaces. The formalism has been extended to obtain a quadrature expression for the screened electrostatic interaction between Janus colloids with variable relative orientations. The interaction is decomposed into three zones in the parametric space, distinguished by their azimuthal symmetry. Different specific situations are examined to estimate the contributions of these zones to the total energy. The effective potential Vpl is renormalized such that the resulting potential energy is identical to the actual one for the most preferable relative orientations between the Janus particles. The po- tential energy as a function of the separation distance and the mutual orientation of a pair of particles compares favorably between the analytical (but approximate) form and the rigorous point-wise computational model used earlier. Coarse-grained models of Janus particles can thus implement this potential model efficiently without loss of generality.
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- Award ID(s):
- 2102455
- PAR ID:
- 10469086
- Publisher / Repository:
- ACS Publications
- Date Published:
- Journal Name:
- The Journal of Physical Chemistry B
- Volume:
- 127
- Issue:
- 7
- ISSN:
- 1520-6106
- Page Range / eLocation ID:
- 1664 to 1673
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1021/acs.jpcb.2c07858
