Figure 7: Cell micro-manipulation with targeted actuation of the HAIRS-xNR material.

(a–e) Images taken from a movie sequence (Supplementary Movie 10) recorded during a cell micro-manipulation experiment showing epifluorescence images of the cells on the left and reflected brightfield images of the underlying microstructures on the right. The cells were cultured on the HAIRS-30NR sample for 24 h before the experiment. The laser is focused at the centre of the pink dashed circle that outlines the area where the hydrogel is contracted and the microplates are actuated. The cells are labelled with the fluorescent CellTracker Green CMFDA dye. Images of two cells before the start of the experiment (a) and of the same cells ∼3 s after the laser (∼18 mW) is initially turned on (c) are shown. The cell on the right undergoes a significant change in shape due to the movement of the microstructures underneath it (b,d). The locations of the two microstructures at both time points are marked by the yellow dashed lines, and the elongation from 9 μm (b) to 13 μm (d) of the portion of the cell overlying that region is indicated by the yellow arrows. The blue bars in the brightfield images mark the locations of the microstructure tips, and highlight the change in the distance separating the tips of adjacent microstructures after the hydrogel contraction is triggered. (e) Epifluorescence and (f) confocal images of the cells immediately after (e) and 2 h after (f) the manipulation experiment (2 × 3 s pulses at ∼18 mW, 1 × 3 s pulse at ∼11 mW, and 2 × 3 s pulses at ∼4 mW). (g) Epifluorescence and (h) confocal images of two cells before (g) and 2 h after (h) a second manipulation experiment (Supplementary Movie 13, fifteen short pulses followed by 5 min of continuous strain at ∼4 mW). Before taking the images shown in (f,h), the cells were stained with Sytox Orange Nucleic Acid Stain as a viability assay. The red arrows point to the cell that was subjected to mechanical perturbations. All scale bars are 10 μm.