Abstract
Outermost occupied electron shells of chemical elements can have symmetries resembling that of monopoles, dipoles, quadrupoles and octupoles corresponding to filled s-, p-, d- and f-orbitals. Theoretically, elements with hexadecapolar outer shells could also exist, but none of the known elements have filled g-orbitals. On the other hand, the research paradigm of ‘colloidal atoms' displays complexity of particle behaviour exceeding that of atomic counterparts, which is driven by DNA functionalization, geometric shape and topology and weak external stimuli. Here we describe elastic hexadecapoles formed by polymer microspheres dispersed in a liquid crystal, a nematic fluid of orientationally ordered molecular rods. Because of conically degenerate boundary conditions, the solid microspheres locally perturb the alignment of the nematic host, inducing hexadecapolar distortions that drive anisotropic colloidal interactions. We uncover physical underpinnings of formation of colloidal elastic hexadecapoles and describe the ensuing bonding inaccessible to elastic dipoles, quadrupoles and other nematic colloids studied previously.
Highlights
Colloids form a platform for scalable fabrication of mesostructured composite materials and provide a framework for testing theoretical descriptions of crystals and glasses, albeit they are commonly encountered in daily life in forms of milk, paints, coffee, fog and so on[1,2,3,4,5]
We describe colloidal elastic hexadecapoles that spontaneously form around solid microspheres immersed in a uniformly aligned Nematic liquid crystal (NLC)
When dispersed in a uniformly aligned NLC fluid host, polystyrene microspheres (PSMs) of a radius r0 locally distort n(r), which is manifested by eight bright lobes around the particle perimeter seen in polarizing optical microscopy (POM) between the crossed polarizer and analyser (Fig. 1a)
Summary
Colloids form a platform for scalable fabrication of mesostructured composite materials and provide a framework for testing theoretical descriptions of crystals and glasses, albeit they are commonly encountered in daily life in forms of milk, paints, coffee, fog and so on[1,2,3,4,5]. Using a combination of holographic optical tweezers (HOT)[19], nonlinear optical imaging[20] and polarizing optical microscopy (POM)[1,6], we probe the n(r)-distortions and quantify colloidal pair interactions by measuring distance and angular dependencies of elastic potentials, demonstrating relations between the director structure and medium-mediated inter-particle forces.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
