1.1 Enhanced contact flexibility from nanoparticles in capillary suspensions
This work reveals how nanoparticles alter capillary suspension behaviors by reducing network heterogeneity and promoting liquid redistribution, as demonstrated by their structural responses under compression. Through confocal microscopy analysis coupled with rheological measurements, we demonstrate that nanoparticles create thin liquid films on microparticle surfaces and have a similar effect on wettability alteration, dramatically changing network dynamics. These films mitigate contactline pinning and facilitate liquid redistribution between bridges, resulting in narrower bridge size distributions and enabling easier particle rearrangement during compression. This investigation also indicates that nanoparticles positioned at microparticle contact regions diminish Hertzian contact, further promoting particle mobility. These combined effects result in capillary suspensions with enhanced contact flexibility, providing more controlled responses to external forces, which is a critical property for applications requiring precise deformation behaviors, particularly in industrial printing and additive manufacturing.
1.2 Dewetting fingering Instability in capillary suspensions: role of particles and liquid bridges
This work examines the complex dewetting phenomena during the rapid stretching of suspensions, capillary suspensions, and capillary nanosuspensions using a modified Hele-Shaw cell with high-speed imaging. Microparticles are shown to enhance finger development through increased particle interactions and nucleation sites, while secondary liquid reduces fingering by creating stronger interparticle networks. Most significantly, the study demonstrates that nanoparticle addition induces earlier cavitation onset and enhances fingering instability while simultaneously reducing sampleto- sample variation. The investigation provides quantitative analysis of dendritic patterns and reveals that nanoparticles transform material failure behavior from adhesive to cohesive, promoting more even distribution between substrates during separation. These insights into high-speed stretching behaviors have substantial implications for printing processes and coating applications where controlled dewetting patterns directly impact product consistency and quality.
1.3 Capillary forces-driven orientation in rod networks
Building on the surface modification effects observed with spherical nanoparticles, this Chapter explores how particle geometry provides an independent mechanism for controlling network properties. This Chapter introduces a novel approach to understanding anisotropic particle networks in capillary suspensions by analyzing single rod orientation, contact morphology, and resulting rheological behaviors. Via 3D particle detection algorithms, we demonstrate how secondary liquid drives a transition from point-to-point to side-to-side particle contacts, dramatically altering 9 mechanical properties. Unlike spherical particle systems, these rod-based networks exhibit an inverse relationship between coordination number and clustering coefficient, indicating the formation of complex assemblies rather than simple side-to-side alignments. Through rheoconfocal measurements, the study captures chaotic cluster movements during yielding transitions, revealing localized mechanical responses invisible to bulk rheological measurements. The research provides a detailed analysis of particle contact types, orientation distributions, and network structural parameters, establishing a predictive framework for designing materials with orientationdependent properties through controlling rod alignment and bridge configurations.
1.4 The mechanisms of yielding: How localized rearrangements drive global failure
This work reveals the mechanisms underlying particle network yielding through direct visualization of a capillary suspension model system using confocal microscopy. By adding small amounts of immiscible secondary liquid to create liquid bridges between particles, we establish a sample-spanning network where bond behavior can be observed directly. Our findings demonstrate that local rigidity deterministically predicts spatially heterogeneous yielding patterns. Visualization of bridge dynamics shows that bond stretching dominates a longer portion of the oscillation cycle compared to bridge retraction, despite the attractive nature of capillary forces. Through sequential analysis of physical processes, we identify distinct rheological fingerprints that demarcate three yielding regimes: an initial reversible region beyond the linear viscoelastic regime characterized by minor reorientations of flexible connections; an irreversible yielding zone in the flow direction marked by bridge stretching and retraction; and a catastrophic connectivity loss between clusters beyond the crossover point. These insights provide a framework for understanding yielding behavior not only in capillary suspensions but across particulate systems more broadly, with implications for industries spanning food production, pharmaceuticals, construction materials, and printed electronics.
1.5 Identifying the precursor of structural failure in attractive gels
In this work, we focus on the yielding behavior of capillary suspensions, combining traditional rheometer and rheoconfocal setups with conventional rheological measurements and novel recovery rheology. Through recovery rheology combined with confocal microscopy, we optically confirmed particle displacement and its agreement with rheologically measured recoverable strains. We performed amplitude sweeps and captured the evolution of local particle configurations throughout the yielding process. Unlike Medium (Large) Amplitude Oscillatory Shear (MAOS/LAOS) analysis, which relies solely on Fourier transformation decomposition of stress response into waves of higher harmonics, our method directly links the development of stress derivatives in bulk with local yielding behavior, both rheologically and optically. This provides the foundation for developing a model that predicts failure patterns under different flow conditions. Additionally, we preliminarily examined the effects 10 of nanoparticles, demonstrating how the contact-line pinning elimination results in lower recoverable strains. Optically, we observed that as interparticle movements become lubricated by nanoparticles, particle movement in the vorticity direction at small strains is also damped.