Shear thickening in densely packed suspensions of spheres and rods confined to few layers

We investigate confined shear thickening suspensions for which the sample thickness is comparable to the particle dimensions. Rheometry measurements are presented for densely packed suspensions of spheres and rods with aspect ratios 6 and 9. By varying the suspension thickness in the direction of the shear gradient at constant shear rate, we find pronounced oscillations in the stress. These oscillations become stronger as the gap size is decreased, and the stress is minimized when the sample thickness becomes commensurate with an integer number of particle layers. Despite this confinement-induced effect, viscosity curves show shear thickening that retains bulk behavior down to samples as thin as two particle diameters for spheres, below which the suspension is jammed. Rods exhibit similar behavior commensurate with the particle width, but they show additional effects when the thickness is reduced below about a particle length as they are forced to align; the stress increases for decreasing gap size at fixed shear rate while the shear thickening regime gradually transitions to a Newtonian scaling regime. This weakening of shear thickening as an ordered configuration is approached contrasts with the strengthening of shear thickening when the packing fraction is increased in the disordered bulk limit, despite the fact that both types of confinement eventually lead to jamming.Comment: 21 pages, 14 figures. submitted to the Journal of Rheolog

Demonstrating Paraflow: Interactive fluid dynamics simulation with real-time visualization for augmented resin 3D printing

While resin 3D printers are seeing growing adoption in both manufacturing and personal fabrication settings, detecting print failures in real time remains challenging. Object-detection neural networks have shown benefits in a variety of extrusion-based 3D printing methods. Here, we extend such work to resin printing using a physics-informed machine learning data generation pipeline. Our approach leverages our models of the fluid dynamics of the printing process at every slice, in order to synthetically generate a library of print defects. We show such an approach is capable of providing data sufficiently resembling real-world failures to fine-tune a pre-trained custom defect detection neural network that can alert users of failure in real-time. Finally, to allow novice users to take advantage of our simulation platform, we integrate our tool into an interactive augmented reality interface, which displays simulation predictions to provide guidance on design and machine parameters prior to printing.Mechanical Engineerin

Developments in CO2 research

CO2 can be a good solvent for many compounds when used in its compressed liq- uid or supercritical fluid state. Above its critical temperature and critical pressure (Tc = 31 °C, Pc = 73.8 bar), CO2 has liquid-like densities and gas-like viscosities, which allows for safe commercial and laboratory operating conditions. Many small molecules are readily soluble in CO2, whereas most macromolecules are not. This has prompted development of several classes of small molecule and polymeric surfactants that enable emulsion and dispersion polymerizations as well as other technological processes

Layerless fabrication with continuous liquid interface production

Despite the increasing popularity of 3D printing, also known as additive manufacturing (AM), the technique has not developed beyond the realm of rapid prototyping. This confinement of the field can be attributed to the inherent flaws of layer-by-layer printing and, in particular, anisotropic mechanical properties that depend on print direction, visible by the staircasing surface finish effect. Continuous liquid interface production (CLIP) is an alternative approach to AM that capitalizes on the fundamental principle of oxygen-inhibited photopolymerization to generate a continual liquid interface of uncured resin between the growing part and the exposure window. This interface eliminates the necessity of an iterative layer-by-layer process, allowing for continuous production. Herein we report the advantages of continuous production, specifically the fabrication of layerless parts. These advantages enable the fabrication of large overhangs without the use of supports, reduction of the staircasing effect without compromising fabrication time, and isotropic mechanical properties. Combined, these advantages result in multiple indicators of layerless and monolithic fabrication using CLIP technology

Delivery of Multiple siRNAs Using Lipid-Coated PLGA Nanoparticles for Treatment of Prostate Cancer

Nanotechnology can provide a critical advantage in developing strategies for cancer management and treatment by helping to improve the safety and efficacy of novel therapeutic delivery vehicles. This paper reports the fabrication of poly(lactic acid-co-glycolic acid)/siRNA nanoparticles coated with lipids for use as prostate cancer therapeutics made via a unique soft lithography particle molding process called PRINT (Particle Replication In Nonwetting Templates). The PRINT process enables high encapsulation efficiency of siRNA into neutral and monodisperse PLGA particles (32–46% encapsulation efficiency). Lipid-coated PLGA/siRNA PRINT particles were used to deliver therapeutic siRNA in vitro to knockdown genes relevant to prostate cancer

Organic Polymer Chemistry in the Context of Novel Processes

This article was written to shed light on a series of what some have stated are not so obvious connections that link polymer synthesis in supercritical CO2 to cancer treatment and vaccines, nonflammable polymer electrolytes for lithium ion batteries, and 3D printing. In telling this story, we also attempt to show the value of versatility in applying one's primary area of expertise to address pertinent questions in science and in society. In this Outlook, we attempted to identify key factors to enable a versatile and nimble research effort to take shape in an effort to influence diverse fields and have a tangible impact in the private sector through the translation of discoveries into the marketplace

Top-Down Particle Fabrication: Control of Size and Shape for Diagnostic Imaging and Drug Delivery

This review discusses rational design of particles for use as therapeutic vectors and diagnostic imaging agent carriers. The emerging importance of both particle size and shape is considered, and the adaptation and modification of soft lithography methods to produce nanoparticles is highlighted. To this end, studies utilizing particles made via a process called Particle Replication In Non-wetting Templates (PRINT™) are discussed. In addition, insights gained into therapeutic cargo and imaging agent delivery from related types of polymer-based carriers are considered

Potent Engineered PLGA Nanoparticles by Virtue of Exceptionally High Chemotherapeutic Loadings

Herein we report the fabrication of engineered poly(lactic acid-co-glycolic acid) nanoparticles via the PRINT® (Particle Replication In Non-wetting Templates) process with high and efficient loadings of docetaxel, up to 40% (w/w) with encapsulation efficiencies >90%. The PRINT process enables independent control of particle properties leading to a higher degree of tailorability than traditional methods. Particles with 40% loading display better in vitro efficacy than particles with lower loadings and the clinical formulation of docetaxel, Taxotere®

Compliant glass–polymer hybrid single ion-conducting electrolytes for lithium batteries

This study describes hybrid single ion-conducting electrolytes based on inorganic sulfide glasses and perfluoropolyether polymers for lithium batteries. Herein, it is shown that hybrid electrolytes provide a compelling alternative to the traditional glass, ceramic, or polymer battery electrolytes. These electrolytes present high transference numbers, unprecedented ionic conductivities at room temperature, and excellent electrochemical stability, and they limit the dissolution of lithium polysulfides. The results in this work represent a significant step toward addressing the challenges of enabling the next generation cathodes, such as lithium nickel manganese cobalt oxide and sulfur

More Effective Nanomedicines through Particle Design

Nanomedicine is an emerging field that applies concepts in nanotechnology to the development of novel diagnostics and therapeutics. Physical and chemical properties of particles, including size, shape, modulus, surface charge and surface chemistry, play important roles in the efficacy of nanomedicines. This review focuses on the effect of particle physical and chemical properties on their interactions with cells in vitro and their pharmacokinetics and biodistribution in vivo