J. Neirynck

Challenges and Best Practices in Modeling Anisotropic Stresses in Soft Polymorphic Materials

J. Neirynck, S. Geerinckx, S.M.J. Rogge

ACS Physical Chemistry Au

2026

A1

Abstract

Soft polymorphic materials, such as metal–organic frameworks (MOFs) and covalent organic frameworks (COFs), often display distinct anisotropy. Yet, their phase transition behavior has been predominantly characterized under isotropic stimuli, such as temperature or pressure variations, up to now. In this work, we employed the Cauchystat to investigate how MIL-53(Al) and COF-5, two prototypical soft porous crystals, respond to anisotropic stresses instead. For MIL-53(Al), we showed that normal stresses induce a phase transition already at stresses below the critical hydrostatic pressure, depending on the directionality of the applied stress. For COF-5, we determined the critical shear stress needed to induce a layer instability, leading to delamination. In both cases, we highlighted the importance of selecting adequate values of the Cauchystat control parameters to obtain accurate predictions. Based on these insights, we formulated best practices to simulate phase transitions in soft porous crystals under nonhydrostatic loadings, which is required for, e.g., nanosensors and -dampers.

Gold Open Access

DOI

http://dx.doi.org/10.1021/acsphyschemau.5c00141

Electrically Switchable Multi-Stable Topological States Enabled by Surface-Induced Frustration in Nematic Liquid Crystal Cells

J. Neirynck, Y.-T. Hsiao, M. Stebryte, I. Nys

Advanced Materials

37, 12, 2414675

2025

A1

Abstract

In liquid crystal (LC) cells, the surface patterning directs the self-assembly of the uniaxial building blocks in the bulk, enabling the design of stimuli-response optical devices with various functionalities. The combination of different anchoring patterns at both substrates can lead to surface induced frustration, preventing a purely planar and defect-free configuration. In cells with crossed assembly of rotating anchoring patterns, elastic deformations allow to obtain a defect-free bulk configuration, but an electrical stimulus can induce disclination lines. The disclination network is preserved without applied voltage. Depending on the electric field treatment and geometrical parameters, different multi-stable states with and without disclinations are obtained. This is demonstrated with the help of dual-frequency LCs, for which the frequency dependent dielectric properties allow repeatable switching between multi-stable states. Topological protection and the associated energy barrier between different states explains the observed metastability. The obtained configurations are retrieved with Q-tensor simulations and the validity is confirmed by matching optical simulations with experimentally obtained microscopy images. The realized multi-stable topological states interact differently with light, resulting in distinct optical properties. Optimization allows to switch between a highly transparent state and an opaque state, opening up opportunities for smart windows with low energy consumption.