Fig. 1: Synthesis and growth mechanism of piezoelectric DL-alanine biocrystal network.

a Large-area optical microscope image of a DL-alanine truss-like network. Inset is a digital photograph of the network grown on a Si wafer substrate. b AFM topography images of a single DL-alanine MF (top) and a zoomed-in image showing the fibrous surface feature (bottom). c SEM image of an intersection area including both bifurcation and merging features of the MF network. d AFM topography image of a bifurcation region. Right-panel compares the height profiles of two MFs at the bifurcated region (top) and after bifurcation (bottom) as marked by the dashed lines in the AFM image. e XRD spectra of as-prepared truss-like DL-alanine MF network (red) and DL-alanine raw powders (black). f 2D XRD of DL-alanine network (top) and DL-alanine raw powders (bottom). g Schematics illustrating the branching process of DL-alanine MFs driven by solvent-molecular interaction and surface tension. L alanine and D alanine molecules are indicated by red arrows. Bottom left inset: optical microscope image showing the small contact angle at the DL-alanine MF and water interface. Bottom right inset: SEM image showing a MF with a developing branch.