Alexandra Victoria Bayles

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Bayles

First Name

Alexandra Victoria

ORCID

0000-0001-9689-9361

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Publications 1 - 8 of 8

Divide, Conquer, and Stabilize: Engineering Strong Fluid-Fluid Interfaces
Bayles, Alexandra Victoria; Vermant, Jan (2022)
Langmuir
In multiphase materials, structured fluid-fluid interfaces can provide mechanical resistance against destabilization. Coarsening, coalescence, and significant deformation can be stalled with appropriate interfacial rheology and thus preserve interface integrity. Often, interfacial "strength"is generated by dense, packed surface populations, which are challenging to achieve through gradual, equilibrium-limited adsorption. Recent efforts have focused on developing new methods to produce kinetically trapped interfacial structures that possess desirable viscoelasticity or viscoplasticity, sometimes even with sparse populations. In creating these interfaces, we should recognize that the processing history is deterministic and offers alternative handles to engineer useful rheology. In this Perspective, we consider what can be achieved by designing not only the intrinsic qualities of surface-active species but also the process that brings them to the interface. We contrast different classes of processing history through a somewhat historical lens: after creating an interface ("divide"), what ("conquering") strategies exist for populating it with agents that ensure stabilization? Navigating the delicate interplay among property, structure, and processing history is required to improve material and energy use and to realize unique multiphase materials.
Engineering Gelation Kinetics in Living Silk Hydrogels by Differential Dynamic Microscopy Microrheology and Machine Learning
Martineau, Rhett L.; Bayles, Alexandra Victoria; Hung, Chia-Suei; et al. (2022)
Advanced Biology
Microbes embedded in hydrogels comprise one form of living material. Discovering formulations that balance potentially competing for mechanical and biological properties in living hydrogels-for example, gel time of the hydrogel formulation and viability of the embedded organisms-can be challenging. In this study, a pipeline is developed to automate the characterization of the gel time of hydrogel formulations. Using this pipeline, living materials comprised of enzymatically crosslinked silk and embedded E. coli-formulated from within a 4D parameter space-are engineered to gel within a pre-selected timeframe. Gelation time is estimated using a novel adaptation of microrheology analysis using differential dynamic microscopy (DDM). In order to expedite the discovery of gelation regime boundaries, Bayesian machine learning models are deployed with optimal decision-making under uncertainty. The rate of learning is observed to vary between artificial intelligence (AI)-assisted planning and human planning, with the fastest rate occurring during AI-assisted planning following a round of human planning. For a subset of formulations gelling within a targeted timeframe of 5-15 min, fluorophore production within the embedded cells is substantially similar across treatments, evidencing that gel time can be tuned independent of other material properties-at least over a finite range-while maintaining biological activity. © 2120 Wiley-VCH GmbH.
Hydrogen Bonding Strength Determines Water Diffusivity in Polymer Ionogels
Bayles, Alexandra Victoria; Fisher, Julia M.; Valentine, Connor S.; et al. (2021)
The Journal of Physical Chemistry B
Polymeric ionogels, cross-linked gels swollen by ionic liquids (ILs), are useful vehicles for the release and storage of molecular solutes in separation, delivery, and other applications. Although rapid solute diffusion is often critical for performance, it remains challenging to predict diffusivities across multidimensional composition spaces. Recently, we showed that water (a neutral solute) diffuses through alkyl-methylimidazolium halide ILs by hopping between hydrogen bonding sites on relatively immobile cations. Here, we expand on this activated hopping mechanism in two significant ways. First, we demonstrate that water diffuses through poly(ethylene glycol)diacrylate ionogels via the same mechanism at a reduced rate. Second, we hypothesize that the activation energy barrier can be determined from relatively simple H-1 NMR chemical shift measurements of the proton responsible for H-bonding. This relationship enables water's diffusivity in ionogels of this class to be predicted quantitatively, requiring only (1) the composition-dependent diffusivity and Arrhenius behavior of a single IL and (2) H-1 NMR spectra of the ionogels of interest. High-throughput microfluidic Fabry-Perot interferometry measurements verify prediction accuracy across a broad formulation space (four ILs, 0 <= x(H2O) <= 0.7, 0 = phi(PEGDA) <= 0.66). The predictive model may expedite IL-material screening; moreover, it intimates a powerful connection between solute mobility and hydrogen bonding and suggests targets for rational design.
Rapid Manufacturing of High-Permittivity Dielectric Elastomer Actuator Fibers
Danner, Patrick M.; Pleij, Tazio; Liechti, Florent; et al. (2025)
Advanced Materials Technologies
The fast and scalable production of dielectric elastomer actuators (DEAs) remains the major bottleneck preventing the widespread use of DEAs. In this work, an ultra-fast production method is presented for dielectric elastomer fibers which can reach industrial-like extrusion speeds of up to 60 mm s$^{-1}$ of fiber, leading to a production speed of up to 16.7 m of fiber per second or 216 m per hour. Electrode and high permittivity (ε' = 11.2) dielectric inks are used with a long pot life, but ultra-fast cross-linking at elevated temperatures. The process eliminates the need for tedious and time-consuming post-processing, as simple co-extrusion and laser ablation enable the production of fully functional, high-permittivity DEA fibers within seconds. This work represents a significant advancement in DEA manufacturing, transitioning from conventional layer-by-layer batch production to continuous co-extrusion-based manufacturing. To the best of the knowledge, this is currently the fastest method for fabricating fully functional DEAs in a single processing step.
Stretch, fold, and break: Intensification of emulsification of high viscosity ratio systems by fractal mixers
Hofmann, Martin; Bayles, Alexandra Victoria; Vermant, Jan (2021)
AIChE Journal
During emulsification process design, the bulk and interfacial rheology of the target formulation must be carefully considered. Formulations with high viscosity ratios and/or finite interfacial elasticity are particularly challenging to emulsify, as conventional drop-breakup methods consume significant energy and provide limited control over polydispersity. Here, we develop a two-stage process that produces monodisperse emulsions from high viscosity ratio constituents. In the first stage, a custom static mixer generates co-flowing layers of alternate phases, and progressively thins layers until they rupture, thus forming a high-internal phase emulsion. The interfacial properties and flow conditions that promote stable fractal multiplication are discussed. In the second stage, extensional flow elements refine the polydispersity. We demonstrate the utility of this novel process by producing remarkably monodisperse polyisobutylene-in-water emulsions with an energy efficiency that is orders of magnitude higher than classical emulsification methods. The moderate throughputs achieved show promise for upscaling and intensification in industrial applications.
Efficient Processing Pathways to Create High Interface Materials
Schaller, Raphael; Hoffmann, M.; Bayles, Alexandra Victoria; et al. (2020)
Soft Matter Series ~ Bijels: Bicontinuous Particle-stabilized Emulsions
Whereas physical chemistry and phase separation of the constituents can be used to direct the organization of multiphase materials, processing flows could be an alternative to create intricate multiphase structures. Generating interfaces on the bulk scale through traditional batch- or continuous-mixing processes is, however, energy and material intensive, and offers poor control. Here, we discuss an alternative based on interface creation using laminar flow in specific static mixers that force immiscible streams through splitting and recombination elements, which multiplies the layers per unit volume in a fractal manner and maximizes the area of interfacial contact. These techniques have mainly been used for polymeric systems so far, but the notion of hierarchical and fractal processing can be extended to other classes of soft materials. Increasingly thin multilayered liquid structures are remarkably stable, leading to very small droplets when they finally break up, thus opening a possible route towards energy-efficient emulsification, as will be discussed at the end of this chapter.
Advective Assembler-Enhanced Support Bath Rotational Direct Ink Writing
Pleij, Tazio; Bayles, Alexandra Victoria; Vermant, Jan (2024)
Advanced Materials Technologies
Manufacturing intricately controlled, hierarchically distributed structures poses significant fabrication challenges, but is crucial for enhancing functionality in synthetic systems. A 3D printing technique combining advective assembly with rotational direct ink writing is developed and exploited to build topologically complex, multimaterial structures with high precision. A modular advective assembler printhead is fabricated and employed in the process. This flow-structuring device is designed with a complex network of internal channels that patterns flowing hydrogel-based inks, creating multi-layered filaments whose structures go well beyond conventional nozzle shape and size limitations. The composite filaments are extruded into a rotating support bath of Polyacrylic acid microgels. The rheology of the inks and support bath are critical to maintain print fidelity and integrity, and are characterized by linear and nonlinear bulk rheometry. Optimization of the materials creates a platform where curvilinear, multimaterial architectures are constructed without being constrained to slicing across X, Y, and Z axes. The versatility of this manufacturing platform is demonstrated by printing helical structures that undergo swelling-induced actuation. This processing method has the potential to significantly enhance additive manufacturing by enabling the production of intricate, multiscale composite structures with broad applicability in fields such as bioengineering, soft robotics, and functional composite materials.
Structuring Hydrogel Cross-Link Density Using Hierarchical Filament 3D Printing
Bayles, Alexandra Victoria; Pleij, Tazio; Hofmann, Martin; et al. (2022)
ACS Applied Materials & Interfaces
Polymer hydrogels, water-laden 3D cross-linked networks, find broad application as advanced biomaterials and functional materials because of their biocompatibility, stimuli responsiveness, and affordability. The cross-linking density reports material properties such as elasticity, permeability, and swelling propensity. However, this critical design parameter can be challenging to template locally. Here, we report a continuous processing scheme that uses laminar flow to direct the organization of cross-linking density across a single sample. Dilute and concentrated poly(ethylene glycol) diacrylate solutions are fed into custom serpentine millifluidic devices. These feature a modular sequence of splitting, rotation, and recombination elements, which create patterned streamlines that serve as a template for hierarchical concentration distributions. Poly(acrylic acid) microgels impart viscoplasticity, which stabilizes layered flow during multiplication and ensures reliable advection. The devices produce structured, seamless filaments, which are then arranged into objects using 3D printing, and photopolymerized to secure the heterogeneous distribution. The flow-encoded, multiscale architecture provides mechanical contrast, which is demonstratively exploited to program robust and reversible shape transformations, potentially useful in soft actuator and sensor applications. The unique structures achieved, and the geometrically dictated, chemistry-agnostic operating principles used to achieve them, provides a new means to engineer hydrogels to suit a variety of applications.

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Alexandra Victoria Bayles

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