We describe a contactless heat engine in which quantum and thermal electromagnetic fluctuations act as the working medium. The setup consists of two concentric cylinders held at different temperatures. The inner cylinder stably levitates within the outer one due to repulsive nonequilibrium Casimir forces. The chirality of the setup is broken by using nonreciprocal dielectric materials, akin to application of a magnetic field along the common cylinder axis. Using Rytov fluctuational electrodynamics, we show that heat transfer and torque can be expressed in terms of an angular-momentum-resolved heat flux density, Φn(ω): each exchanged photon carries energy ℏω and angular momentum ℏn. In reciprocal media, contributions from modes n and -n cancel and there is no net torque; nonreciprocity breaks this symmetry and powers rotation of the inner cylinder. Even in the absence of contact, electromagnetic fluctuations produce a frictional torque opposing rotation that we compute. This enables computation of characteristic steady state rotations, and estimation of the engine efficiency (which remains bounded by the Carnot limit). The cylindrical setup provides a natural realization of fluctuation-induced angular-momentum transfer and a possible route toward nanoscale contactless engines.

The nozzle geometries associated with extrusion-based 3D printing impart significant spatial heterogeneities in both the type (shear vs extension) and rate of the flows applied during extrusion. For polymeric and nanostructured inks, these heterogeneous flow histories influence the underlying structure at the nano- to microscale. We previously demonstrated that HOT-DIW 3D printing can orient the nanostructure of a cylinder-forming block copolymer along a programmed print path, enabling tunable mechanical anisotropy. To probe the subfilament heterogeneities in nanostructure that arise in these oriented materials from the spatially varied flow histories, we apply scanning microbeam small-angle X-ray scattering (SM-SAXS). From this data, we identify a flow-rate-dependent emergence of off-axis tilted domains, which develop upon thermal annealing. We propose that application of shear followed by extension during 3D printing imparts asymmetric stretching of bridging chain conformations. Relaxation of this trapped stress upon thermal annealing imparts a torque on the shortened polystyrene domains which drives the formation of long-range ordered cylinders at an angle offset to the print direction. We show that the distribution of tilts within 3D-printed filaments is consistent with the variability in printed filament stiffness. Ultimately, these flow-structure insights highlight the need to understand how "real" mixed flows of complex fluids such as block copolymer melts drive the assembly, structure, and properties of printed materials.