Fabrication of contact-free and in-contact devices

A cw green laser beam (λ = 532 nm) is tightly focused into the sample by an oil-immersion (NA = 1.3) objective lens. The sample is translated in 3D space following a controllable trajectory by a high-resolution Piezoelectric Nanopositioning system (P-563 PIMars, PI). The structures are fabricated using different powers (from 10 μW to 40 mW) and different scanning speeds (from 1 μm/s to 8 μm/s). Due to an optically induced thermal effect at the focusing spot, the fabricated structures are completely polymerized (cross-linked) after the scanning (see Fig. S²(a)-Supporting Information) without the post-exposure baking process. Within the structures, the MNPs and QD are preserved in a coupled position. Meanwhile the ones in the SU-8 monomers are removed by the development step. The contact-free structures have a radius of 3 μm, a width of 400 nm for the micro-wheel structure, and a length of 8 μm for the micro-arrow structure.Before releasing the contact-free devices from the glass substrate, a distance from the fabricated structures to the substrate must be considered (about few μm). The monomers layer under the pattern will act as a sacrificial layer which allows one to release the structures into the solution. In contrast with contact-free structures, the in-contact structures were fabricated from the interface of the polymer and the substrate so that the structures are fixed on the glass substrate and thus unable to be manipulated externally. The design dimensions of the in-contact device have a radius R, micro-wheel linewidth W_wheel, nano-coil linewidth W_coil, vertical pitch P, length of spring L, and number of turns, N, which are 3 μm, 1 μm, 0.5 μm, 1.5 μm, 7 μm and 4, respectively. (see Fig. S²(b) - Supplementary Information). To develop the structures, the samples were emerged in SU-8 developer, then in isopropannol, and finally in distilled water for 2 minutes to get rid of unexposed parts and leaving the desired structures on the glass substrate.