Figure 6: Levitational and guided self-assembly of micro-components using radicals.

(a) Simulation of magnetic field norm (contour) and flux density (arrows) created by two magnets in anti-Helmholtz configuration. (b,c) 1 × 1 cm² 20% PEGDMA hydrogels in a radical solution reservoir; before (b) and after (c) being placed into a magnetic setup composed of permanent NdFeB magnets in anti-Helmholtz configuration (same poles facing each other). Hydrogels are levitated due to the paramagnetism of radical solution. (d,e) Non-radicalized (left) and radicalized (right) 1 × 1 cm² hydrogels in Gadolinium (Gd) solution; before (d) and after (e) being placed into magnetic setup. Radicalized hydrogel did not levitate because of cancelling effects between paramagnetism of radicals and Gd ion salts, whereas non-radicalized hydrogel levitated because of paramagnetism of Gd solution. (f,g) Non-radicalized (yellow) and radicalized (blue) 1 × 1 mm² hydrogels in Gd solution; before (f) and after (g) being placed into the magnetic setup. Radicalized hydrogels (blue) did not levitate because of cancelling effects between paramagnetism of radicals and Gd ion salts, whereas non-radicalized hydrogels (yellow) were levitated and assembled because of the paramagnetism of Gd solution. (h–j) Levitational guided self-assembly of 500 μm polystyrene beads. Quantification of assembly areas as a function of time for beads in Gd and radical solution (h). Error bars represent s.d. from the mean. Snapshots are given before (i) and after (j) assembly in radical solution.