Fig. 2: Co-assembly, structure, properties, and biofabrication of the ELK1–GO system.

a Time-lapse images illustrate the dynamic properties of the ELK1–GO membrane first (a-Top forming a closed sac when a drop of ELK1 solution is immersed in a larger GO solution and second (a-Bottom) opening upon touching an interface within the first seconds of formation. b The membrane exhibits a multi-layered architecture of about 50 μm thick comprising aligned GO sheets throughout (birefringence inset) interacting with ELK1 molecules (fluorescence image, green: ELK1, red: GO), c which are observed to decrease in concentration from the inside to the outside as evidenced by wavelength-dispersive spectroscopy (WDS). Only ELK1 comprises nitrogen in its molecular structure. ±s.d. for n = 3. *p < 0.05. t test. d The system enables growing the membranes into longer tubes on demand by displacing an interface. e The robustness of the system enables formation of capillaries down to about 50 μm in internal diameter with 10 μm thick walls, f bridging of surfaces simply by touching two interfaces while injecting one solution into the other, and g co-assembling in salt solutions, opening the possibility to embed cells (green identified by white arrows) within the membrane (outlined by dashed lines) as the tubes are formed. The images are taken after 24 h of culture and correspond to a live (green)/dead (red) assay. Scanning electron micrographs of cells embedded within layers of GO (top) and a cross-section of the ELK1–GO membrane comprising cells within different layers (bottom). h–l Images demonstrate the versatility of the co-assembly system by incorporating it with 3D printing to fabricate well-defined fluidic devices consisting of high-aspect ratio tubular structures (h) of different internal diameters and comprising curves, angles of different sizes, and bifurcations (h, i, l) capable of withstanding flow within a few minutes of formation (j, k).