Bioinspired large-scale aligned porous materials assembled with dual temperature gradients

TLDR

Natural porous materials such as bone, teeth, shells, and wood exhibit exceptional strength and toughness, inspiring the design of lightweight, robust composites, yet achieving long‑range porosity order and precise architecture remains challenging, hindering large‑scale fabrication. The study introduces a bidirectional freezing method to assemble ceramic particles into centimeter‑scale, aligned, lamellar, nacre‑like porous scaffolds. The method uses a PDMS‑wedge‑modified cold finger to impose dual temperature gradients, controlling ice nucleation and growth during freezing. The technique offers a promising route to produce bioinspired structural materials, especially composites, by enabling higher structural control.

Abstract

Natural materials, such as bone, teeth, shells, and wood, exhibit outstanding properties despite being porous and made of weak constituents. Frequently, they represent a source of inspiration to design strong, tough, and lightweight materials. Although many techniques have been introduced to create such structures, a long-range order of the porosity as well as a precise control of the final architecture remain difficult to achieve. These limitations severely hinder the scale-up fabrication of layered structures aimed for larger applications. We report on a bidirectional freezing technique to successfully assemble ceramic particles into scaffolds with large-scale aligned, lamellar, porous, nacre-like structure and long-range order at the centimeter scale. This is achieved by modifying the cold finger with a polydimethylsiloxane (PDMS) wedge to control the nucleation and growth of ice crystals under dual temperature gradients. Our approach could provide an effective way of manufacturing novel bioinspired structural materials, in particular advanced materials such as composites, where a higher level of control over the structure is required.