# Experimental and Computational Investigation of Surface‐Responsive Riboflavin‐Based Self‐Assembled Systems

## TL;DR

This study explores how riboflavin self-assembles into crystals that change shape based on the surface they grow on, offering insights into creating adaptable, bio-inspired materials.

## Contribution

The discovery of a new riboflavin co-crystal with surface-responsive self-assembly and tunable electromechanical properties.

## Key findings

- Riboflavin forms branched, twisted, and serrated micron-scale structures on copper, mica, and silicon surfaces.
- The crystal's low Young's modulus enables lattice flexibility and surface-directed morphological adaptation.
- The study links molecular packing and supramolecular interactions to macroscopic electromechanical responses.

## Abstract

Metabolites, including amino acids, nucleobases, and vitamins, have emerged as promising candidates for sustainable functional materials due to their inherent biocompatibility and low fabrication costs. Notable examples include glycine‐based nanogenerators, indigo‐based organic transistors, and caffeine‐based optical waveguides. Riboflavin (vitamin B2), forms optically active supramolecular structures in the tapetum lucidum of lemurs and cats; however, its detailed packing and functional role remain unknown. Here, aiming to explore the bio‐inspired self‐assembly of riboflavin to uncover potential device applications, we discovered and extensively characterized a new single co‐crystal using a combination of crystallography, microscopy, and mechanical experiments supported by atomistic molecular models to understand the organization on different surfaces. The crystals exhibit pronounced surface responsiveness, leading to the formation of distinct branched, twisted, and serrated micron‐scale morphologies as the riboflavin self‐assembled on different substrates of copper, mica, and silicon. This intrinsic ability to adapt shape and generate substrate‐templated structures was confirmed computationally and experimentally and was attributed mainly to the crystal's relatively low Young's modulus, reflecting its lattice flexibility. This structure–function study of an adaptable metabolite crystal offers fundamental insights into how molecular organization governs mechanical responsiveness, advancing the understanding of bio‐inspired crystallization and paving the way for future technological applications.

A self‐assembled crystal of riboflavin exhibits responsive modes of surface‐directed molecular assembly, accompanied by measurable electromechanical properties. This behavior highlights how subtle variations in molecular packing and supramolecular interactions at the crystal interface can directly influence macroscopic functional responses. By bridging the molecular organization with emergent physical properties, these findings elucidate key structure–function relationships, offering new perspectives for the design of bioinspired materials with tunable electromechanical properties.