Infrared spectroscopy of live cells from a flowing solution using electrically-biased plasmonic metasurfaces

Microfluidics, dielectrophoresis (DEP) and metasurface-enhanced infrared reflection spectroscopy (MEIRS) are combined for capturing and rapid spectroscopy of live cells.

Polyacrylamide Adsorption and Readsorption in Sandstone Porous Media

Summary The term polymer retention describes all mechanisms that remove the polymer from the flowing solution, with adsorption being its primary cause. This phenomenon can lead to detrimental effects during polymer enhanced oil recovery (EOR). In this paper, we present an investigation of dynamic polymer adsorption in sandstone-outcrop cores using polymer solutions. We study the effects of permeability and polymer concentration on the adsorption under two conditions: on virgin cores (adsorption) and a previously polymer-flooded core (readsorption). According to the results, two concentration plateaus and two regions of concentration-dependent adsorption characterize the polymer adsorption in a virgin porous medium, following a proposed Type IV isotherm. The transition between the first plateau and the second adsorption region occurs near to the overlapping concentration from dilute to semidilute regimes (cp*). Polymer readsorption increases slightly with the successive injection of banks with a higher polymer concentration, following a Type I (Langmuir) isotherm. For that case, we propose a readsorption mechanism on the basis of the desorption of a polymer molecule section and the adsorption of a new free polymer molecule. The adsorption and readsorption isotherms are similar until cp*, while the adsorption is much higher than readsorption for concentrations higher than cp*. Therefore, if the polymer concentration of the mobility control bank is greater than cp*, the total polymer loss during field applications can be reduced by preinjecting a polymer bank of lower concentration.

Self-Limiting Electrospray Deposition for the Surface Modification of Additively Manufactured Parts

Electrospray deposition (ESD) is a spray coating process that utilizes a high voltage to atomize a flowing solution into charged microdroplets. These self-repulsive droplets evaporate as they travel to a target substrate, depositing the solution solids. Our previous research investigated the conditions necessary to minimize charge dissipation and deposit a thickness-limited film that grows in area over time through self-limiting electrospray deposition (SLED). Such sprays possess the ability to conformally coat complex three-dimensional objects without changing the location of the spray needle or orientation of the object. This makes them ideally suited for the post-processing of materials fabricated through additive manufacturing (AM), opening a paradigm of independent bulk and surface functionality. Having demonstrated three-dimensional coating with film thickness in the range of 1-50 µm on a variety of conductive objects, in this study we employed model substrates to quantitatively study the technique’s limits with regard to geometry and scale. Specifically, we examined the effectiveness of thickness-limited ESD for coating recessed features with gaps ranging from 50 µm to 1 cm, as well as the ability to coat surfaces hidden from the line-of-sight of the spray needle. This was then extended to the coating of hydrogel structures printed by AM, demonstrating that coating could be conducted even into the body of the structures as a means to create hydrophobic surfaces without affecting the absorption-driven humidity response.

Self-Limiting Electrospray Deposition for the Surface Modification of Additively Manufactured Parts

Electrospray deposition (ESD) is a spray coating process that utilizes a high voltage to atomize a flowing solution into charged microdroplets. These self-repulsive droplets evaporate as they travel to a target substrate, depositing the solution solids. Our previous research investigated the conditions necessary to minimize charge dissipation and deposit a thickness-limited film that grows in area over time through self-limiting electrospray deposition (SLED). Such sprays possess the ability to conformally coat complex three-dimensional objects without changing the location of the spray needle or orientation of the object. This makes them ideally suited for the post-processing of materials fabricated through additive manufacturing (AM), opening a paradigm of independent bulk and surface functionality. Having demonstrated three-dimensional coating with film thickness in the range of 1-50 µm on a variety of conductive objects, in this study we employed model substrates to quantitatively study the technique’s limits with regard to geometry and scale. Specifically, we examined the effectiveness of thickness-limited ESD for coating recessed features with gaps ranging from 50 µm to 1 cm, as well as the ability to coat surfaces hidden from the line-of-sight of the spray needle. This was then extended to the coating of hydrogel structures printed by AM, demonstrating that coating could be conducted even into the body of the structures as a means to create hydrophobic surfaces without affecting the absorption-driven humidity response.