Showing papers by "Greg G. Qiao published in 2022"

3D nanoprinting via spatially controlled assembly and polymerization

Abstract: Abstract Macroscale additive manufacturing has seen significant advances recently, but these advances are not yet realized for the bottom-up formation of nanoscale polymeric features. We describe a platform technology for creating crosslinked polymer features using rapid surface-initiated crosslinking and versatile macrocrosslinkers, delivered by a microfluidic-coupled atomic force microscope known as FluidFM. A crosslinkable polymer containing norbornene moieties is delivered to a catalyzed substrate where polymerization occurs, resulting in extremely rapid chemical curing of the delivered material. Due to the living crosslinking reaction, construction of lines and patterns with multiple layers is possible, showing quantitative material addition from each deposition in a method analogous to fused filament fabrication, but at the nanoscale. Print parameters influenced printed line dimensions, with the smallest lines being 450 nm across with a vertical layer resolution of 2 nm. This nanoscale 3D printing platform of reactive polymer materials has applications for device fabrication, optical systems and biotechnology.

Mechanochromophore-linked Polymeric Materials with Visible Color Changes.

Abstract: Mechanical force as a type of stimuli for smart materials has obtained much attention in the past decade. Color-changing materials in response to mechanical stimuli have shown great potential in the applications such as sensors and displays. Mechanochromophore-linked polymeric materials, which are a growing sub-class of these materials, are discussed in detail in this review. Two main types of mechanochromophores which exhibit visible color change, summarized herein, involve either isomerization or radical generation mechanisms. This review focuses on their synthesis and incorporation into polymer matrices, the type of mechanical force used, factors affecting the mechanochromic properties, and their applications. This article is protected by copyright. All rights reserved.

Star-Peptide Polymers are Multi-Drug-Resistant Gram-Positive Bacteria Killers.

Abstract: Antibiotic resistance in bacteria, especially Gram-positive bacteria like Staphylococcus aureus, is gaining considerable momentum worldwide and unless checked will pose a global health crisis. With few new antibiotics coming on the market, there is a need for novel antimicrobial materials that target and kill multi-drug-resistant (MDR) Gram-positive pathogens like methicillin-resistant Staphylococcus aureus (MRSA). In this study, using a novel mixed-bacteria antimicrobial assay, we show that the star-peptide polymers preferentially target and kill Gram-positive pathogens including MRSA. A major effect on the activity of the star-peptide polymer was structure, with an eight-armed structure inducing the greatest bactericidal activity. The different star-peptide polymer structures were found to induce different mechanisms of bacterial death both in vitro and in vivo. These results highlight the potential utility of peptide/polymers to fabricate materials for therapeutic development against MDR Gram-positive bacterial infections.

Oligomeric Poly(Oxazoline) as Potential Lithium Battery Electrolytes

Abstract: Polymer electrolytes are a promising and inherently suitable material for next generation lithium batteries. Advancement in this field requires the use of new synthetic and fabrication techniques, as well as the investigation of new polymers. Here we report on the development of oligomeric Poly(2-ethyl-2-oxazoline) as a candidate for lithium batteries. By reducing the degree of polymerisation, the glass transition temperature was reduced from 54°C for commercially available 50,000 Da PEtOx to 9.45°C for lab synthesized 890 Da PEtOx. Doping with high concentrations of the lithium salt lithium nitrate, Lithium bis(trifluoromethanesulfonyl)imide, and lithium perchlorate, we demonstrate a glass transition temperature maximum as the polymer electrolyte moves into the polymer-in-salt regime. In this regime we recorded a maximum conductivity of was 3.3 x 10-3 S/cm at 100°C and 67 mol % LiClO4. This study demonstrates the potential for further use of alkyl oxazolines at high lithium salt concentrations and elevated temperatures.

Evaporation reduction and salinity control in microalgae production ponds using chemical monolayers

Abstract: Algae have great potential as a hyper-productive crop to produce food, fuels, and chemicals. However, freshwater availability limits their widespread application. Here we investigate whether chemical monolayers can reduce evaporation in microalgae cultures, and whether algal growth is affected. Thin-film monolayers were formed on the surface of freshwater ( Chlorella vulgaris ) and marine ( Nannochloropsis salina ) algae cultures using ethylene glycol monooctadecyl ether. Monolayers applied daily reduced evaporation in both cultures by 70 % on the first day, and ~50 % by day 3. The cause of the reduced performance was investigated but could not be directly attributed to any particular cellular activity or chemical change. Nannochloropsis was uninhibited by the monolayer, while the growth of Chlorella decreased by 38 % over 3 days. There was no evidence that the monolayer reduced gas exchange (CO 2 /O 2 ), but the reduced growth of Chlorella could have been caused by direct chemical inhibition by the monolayer or the slightly elevated temperature (1–2 °C) resulting from the reduction in evaporative cooling . A techno-economic analysis indicated that water savings could make monolayers economically beneficial, especially in arid climates suited to algae production. In addition, monolayers enable control of salinity in marine production systems. Overall, the application of monolayers to reduce evaporation from outdoor algae cultures has great promise, with testing in outdoor trials an obvious next step. • Monolayer film reduced water loss by 50–70 % in freshwater and marine algae cultures. • Nannochloropsis growth remained uninhibited, while Chlorella reduced by 38 %. • No evidence for reduced CO 2 /O 2 exchange in algal cultures • A cost analysis showed that water savings could make monolayers economically viable. • Monolayers can control the salinity in arid climates suited for marine algal growth.