Void Connectivity and Criticality in the Compression-Induced Gel-to-Glass Transition of Short-Range Attractive Colloids

Gels and attractive glasses-both dynamically arrested states formed through short-range attraction-are commonly found in a range of soft matter systems, including colloids, emulsions, proteins, and wet granular materials. Previous studies have revealed intriguing similarities and distinctions in their structural, dynamic, vibrational, and mechanical properties. However, the microstructural mechanisms underlying the gel-to-glass transition remain elusive. To address this, we investigate uniaxial compression-induced gel collapse using confocal microscopy, which provides experimental access to the relationship between mechanical stress and microstructure. Together with Brownian dynamics simulations, our study reveals two sequential transitions in void structure: from gels with percolating voids to isolated voids, and ultimately to voidless glasses. These transitions are closely linked to a shift from superlinear power-law scaling to explosive divergence toward the packing limit in both normal and deviatoric stresses as a function of volume fraction, particularly at lower temperatures. Understanding these mechanically self-organized transitions and their associated criticality deepens our insight into disordered solids, enabling better control over mechanical properties, interfacial characteristics, and transport behavior in porous materials.