# Lattice bond chains administer kink anisotropy and inform strategies of theophylline crystal self-healing

## TL;DR

This study shows how controlling lattice bonds in theophylline crystals can shape their growth and enable self-healing after damage.

## Contribution

The paper introduces a method to control crystal shape and self-healing through classical growth and lattice bond manipulation.

## Key findings

- Classical growth allows control over crystal shape and dimensions.
- Lattice bond strengths influence growth anisotropy and crystal face development.
- Classically grown crystals can regenerate after mechanical or thermal damage.

## Abstract

How molecular-level understanding of the crystal growth mechanisms and their relation to lattice bonds informs the rational design of crystals with desired shapes and properties has remained elusive. Here we employ theophylline crystals and drive them into classical growth mode, in which the crystals grow molecule-by-molecule and new layers are generated by two-dimensional nucleation. We demonstrate that classical growth allows for controlling the crystal’s shape and dimensions. We correlate the anisotropic responses to the supersaturation of the growth rates of crystal layers and crystal faces to the hydrogen and π−π stacking bond chains in the crystal lattice. The obtained insights suggest strategies to direct the crystal shape to either one-dimensional needles or flat sheets. Moreover, we show that crystals that grow by the classical mode of direct monomer incorporation have the potential to regrow and heal once a defect is introduced by mechanical cut or local thermal subliming of crystalline sections.

•The strengths of the lattice bonds control the growth anisotropy•Crystal growth in the classical regime grants the means to control crystal morphology•Transition between needle and slate crystal shape can be driven by supersaturation•Crystals that grow classically regenerate after the introduction of cuts

The strengths of the lattice bonds control the growth anisotropy

Crystal growth in the classical regime grants the means to control crystal morphology

Transition between needle and slate crystal shape can be driven by supersaturation

Crystals that grow classically regenerate after the introduction of cuts

Chemistry; Physics; Materials science