Flow Programming of Viscoelastic Colloidal Suspensions

We investigate the transient rheological response of particle-laden viscoelastic fluids using piezo-electric-driven high-frequency squeeze flow (TriPav from TriLimited LLC). We identify an appropriate constitutive framework to represent the response of ink-like and paint-like fluids. Leveraging a model of both the system and this class of non-Newtonian fluids, we can generate accurate synthetic data to mimic experiments, and isolate transient rheological properties of the fluid. We then optimize "flow programs" -- complex waveforms composed of sequences of squeeze-pulses that optimize a meaningful objective function. Such time-varying strain histories are commonly used in industrial inkjet printing and paint-deposition technologies to facilitate droplet ejection. Here we will elucidate physical mechanisms that underpin “optimal” waveforms for ejection efficiency (especially in the presence of viscoelasticity), working towards a series of methods to design "flow programs" to achieve rare behavior in fluids.