Vapor-induced phase-separation-enabled versatile direct ink writing.

Versatile printing of polymers, metals, and composites always calls for simple, economic approaches. Here we present an approach to three-dimensional (3D) printing of polymeric, metallic, and composite materials at room conditions, based on the polymeric vapor-induced phase separation (VIPS) process. During VIPS 3D printing (VIPS-3DP), a dissolved polymer-based ink is deposited in an environment where nebulized non-solvent is present, inducing the low-volatility solvent to be extracted from the filament in a controllable manner due to its higher chemical affinity with the non-solvent used. The polymeric phase is hardened in situ as a result of the induced phase separation process. The low volatility of the solvent enables its reclamation after the printing process, significantly reducing its environmental footprint. We first demonstrate the use of VIPS-3DP for polymer printing, showcasing its potential in printing intricate structures. We further extend VIPS-3DP to the deposition of polymer-based metallic inks or composite powder-laden polymeric inks, which become metallic parts or composites after a thermal cycle is applied. Furthermore, spatially tunable porous structures and functionally graded parts are printed by using the printing path to set the inter-filament porosity as well as an inorganic space-holder as an intra-filament porogen.

Using runaway replication to express polyhydroxyalkanoic acid (pha) genes from a novel marine bacterium in enteric bacteria: The influence of temperature and phasins on PHA accumulation.

While plastics have revolutionized our world, plastic waste has serious environmental and economic impacts. Polyhydroxyalkanoic acid (PHA) is a bacterial carbon and energy reserve shown to be both biodegradable and biocompatible and could potentially replace conventional plastics. However, cost-effective mass production remains elusive. Bacteria often accumulate PHA as cytoplasmic granules. PHA synthase creates the PHA polymer from acetoacyl-CoA monomers, while phasins are small multifunctional proteins that are found in abundance on the granule surface. The PHA synthase gene from a novel marine isolate, Vibrio B-18 (or B-18), was placed in the presence or absence of an upstream phasin gene in a runaway replication plasmid using polymerase chain reaction (PCR) technology. Plasmid gene expression may be induced chemically or thermally. Overexpression of the PHA genes was demonstrated by SDS-PAGE analysis, and microscopy was used to detect PHA accumulation in three different enteric bacteria (Escherichia coli, Klebsiella aerogenes, and Shigella flexneri). While the B-18 genes were clearly overexpressed at 41°C, PHA accumulation occurred more readily at the lower (30°C) non-inducing temperature regardless of chemical induction if the phasin gene was present. A mutational analysis confirmed the identity of the start codon for the PHA synthase gene and provided evidence supporting the requirement for phasins to allow for PHA accumulation in the recombinant hosts. The findings described in this study confirm the conclusions obtained from related studies from other laboratories and lend support to the importance of including a phasin gene in addition to the basic genes needed for PHA synthesis and accumulation in recombinant enteric bacteria, such as Escherichia coli, Klebsiella aerogenes, and Shigella flexneri.