Continuous Convective-Sedimentation Assembly of Colloidal Microsphere Coatings for Biotechnology Applications

Abstract

Continuous convective-sedimentation assembly (CCSA) is a deposition method that constantly supplies the coating suspension to the meniscus behind the coating knife by inline injection, allowing for steady-state deposition of ordered colloids (which may include particles or cells or live cell-particle blends) by water evaporation. The constant inflow of suspended particles available for transport to the drying front yields colloidal arrays with significantly larger surface areas than previously described and thus expands the ability of convective assembly to deposit monolayers or very thin films of multiple sizes of particles on large surfaces. Using sulfated polystyrene microspheres as a model system, this study shows how tunable process parameters, namely particle concentration, fluid sonication, and fluid density, influence coating homogeneity when the meniscus is continuously supplied. Fluid density and fluid flow-path sonication affect particle sedimentation and distribution. Coating microstructure, analyzed in terms of void space, does not vary significantly with relative humidity or suspended particle concentration. This study evaluated two configurations of the continuous convective assembly method in terms of ability to control coating microstructure by varying the number of suspended polymer particles available for transport to the coating drying front through variations in the meniscus volume.

Biocatalytic coatings for air pollution control: A proof of concept study on VOC biodegradation

“…This is consistent with the results of Fig. 2 discussed earlier. In this context, the possibilities of latex coatings to develop high surface-to-volume ratio surfaces by different deposition methods capable of generating very thin coatings with high cell densities is starting to be explored (Fidaleo et al, 2014;Jenkins et al, 2013).…”

Biocoatings: A new challenge for environmental biotechnology

“…Some common biocoating deposition techniques include extrusion [34,90,91], spray drying [92], the wire wound rod drawdown Mayer rod coating method [13,67,93], 3-D ink-jet deposition [94] and the convective assembly [12,47,95]. Recently, dielectrophoresis (DEP) has also been used to generate photoreactive cyanobacteria cell monolayers on top of polyelectrolyte adhesives [96].…”

“…Kumnorkaew et al [97] demonstrated that when the meniscus height is larger than the particle diameter, multilayer coatings will form [97]. The number and type of layers is easily adjusted by altering the suspension volume fraction and coating knife speed, allowing for precise control in particle packing and coating thickness [95,97,98] (Fig. 2B).…”

Ink-Jet Printing of Gluconobacter oxydans: Micropatterned Coatings As High Surface-to-Volume Ratio Bio-Reactive Coatings

“…Further optimization of the latex coating emulsion and ink-jet printing system (not the focus of this work) will allow for the generation of significantly more surface area and an increased number of reactive cells per coating microstructure. Improvements in surface area as a function of aspect ratio can be seen in Table 2, where ink-jet coatings are compared with a monolayer of G. oxydans cells, as could be obtained by convective-sedimentation assembly [50]. Increased available surface area can come through improving ink-jet methods (ink formulation, droplet control).…”