Imprinting macroscopic fracture during gelation: A mechanism for tuning colloidal gels

In many practical situations -- whether during casting, 3D printing, or more generally processing -- colloidal suspensions of attractive particles undergo gelation while being subjected to repeated deformations. Although such flows are ubiquitous in industrial and laboratory settings, their impact on the emergence of the gel network remains poorly understood. Here, the authors show that applying oscillatory deformations on a colloidal suspension as it turns into a soft solid can imprint fracture patterns that lead to weaker gels compared to quiescent gelation, while enhancing their ability to dissipate energy. Remarkably, these cracks leave a simple and robust mechanical signature that can be captured by a minimal model, linking fracture to bulk material response. Their results reveal how mechanical perturbations reshape gelation and provide a practical route to design softer, more ductile materials.