scholarly journals Enhanced sample filling and discretization in thermoplastic 2D microwell arrays using asymmetric contact angles

2020 ◽  
Vol 14 (1) ◽  
pp. 014113
Author(s):  
S. Padmanabhan ◽  
J. Y. Han ◽  
I. Nanayankkara ◽  
K. Tran ◽  
P. Ho ◽  
...  
Keyword(s):  
Contact Angles ◽  
Asymmetric Contact

Meniscus and viscous forces during separation of hydrophilic and hydrophobic smooth/rough surfaces with symmetric and asymmetric contact angles

2008 ◽  
Vol 366 (1870) ◽  
pp. 1627-1647 ◽  
Author(s):  
Shaobiao Cai ◽  
Bharat Bhushan
Keyword(s):  
Contact Angle ◽  
Hydrophobic Surface ◽  
Separation Distance ◽  
Contact Angles ◽  
Viscous Force ◽  
Meniscus Force ◽  
Meniscus Height ◽  
Viscous Forces ◽  
Separation Time ◽  
Asymmetric Contact

Adhesive or repulsive forces contributed by both meniscus and viscous forces can be significant and become one of the main reliability issues when the contacting surfaces are ultra smooth, and the normal load is small, as is common for micro/nano devices. In this study, both meniscus and viscous forces during separation for smooth and rough hydrophilic and hydrophobic surfaces are studied. The effects of separation distance, initial meniscus height, separation time, contact angle and roughness are presented. Meniscus force decreases with an increase of separation distance, whereas the viscous force has an opposite trend. Both forces decrease with an increase of initial meniscus height. An increase of separation time, initial meniscus height or a decrease of contact angle leads to an increase of critical meniscus area at which both forces are equivalent. An increase in contact angle leads to a decrease of attractive meniscus force but an increase of repulsive meniscus force (attractive or repulsive dependent on hydrophilic or hydrophobic surface, respectively). Contact angle has a limited effect on the viscous force. For asymmetric contact angles, the magnitude of the meniscus force and the critical meniscus area are in between the values for the two angles. An increase in the number of surface asperities (roughness) leads to an increase of meniscus force; however, its effect on viscous force is trivial. A slightly attractive force is observed for the hydrophobic surface during the end stage of separation though the magnitude is small. The study provides a fundamental understanding of the physics of the separation process and it can be useful for control of the forces in nanotechnology applications.

Flexographic ink-coating interactions: effects of latex variations in coating layers

TAPPI Journal ◽  
2016 ◽  
Vol 15 (4) ◽  
pp. 253-262 ◽  
Author(s):  
ERIK BOHLIN ◽  
CAISA JOHANNSON ◽  
MAGNUS LESTELIUS
Keyword(s):  
Contact Angles ◽  
High Ratio ◽  
Print Quality ◽  
Particle Sizes ◽  
Mixed Composition ◽  
Coating Surface ◽  
Covered Area ◽  
Surface Optical ◽  
Flexographic Printing ◽  
Coating Formulation

The effect of coating structure variations on flexographic print quality was studied using pilot-coated paperboard samples with different latex content and latex particle sizes. Two latexes, with particle sizes of 120 nm and 160 nm, were added at either 12 parts per hundred (pph) or 18 pph to the coating formulation. The samples were printed with full tone areas at print forces of 25 N and 50 N in a laboratory flexographic printing press using a waterbased ink. A high ratio of uncovered areas (UCAs) could be detected for the samples that contained 18 pph latex printed at a print force of 25 N. UCAs decreased with increased print force and with decreased amounts of latex in the coating formulation. The fraction of latex covered area on the coating surface was estimated to be 0.35–0.40 for the 12 pph, and 0.70–0.75 for the 18 pph samples. The ink penetration depth into the coating layer could be linked to the fraction of latex-free areas on the coating surface. Optical cross section microscopy indicated that a higher printing force did not increase the depth of penetrated ink to any greater extent. Higher printing force did increase contact between plate and substrate, leading to an improved distribution of the ink. This, in turn, increased print density and decreased UCAs. On closer inspection, the UCAs could be categorized as being induced by steep topographic changes. When appearing at other locations, they were more likely to be caused by poor wetting of the surface. To understand the wetting behavior of the coating surface, observed contact angles were compared with calculated contact angles on surfaces of mixed composition.

Influence of Polymer Charge, Temperature, and Surfactants on Surface Sizing of Liner and Greaseproof Paper With Hydrophobically Modified Starch

TAPPI Journal ◽  
2009 ◽  
Vol 8 (2) ◽  
pp. 33-38 ◽  
Author(s):  
ANNA JONHED ◽  
LARS JÄRNSTRÖM
Keyword(s):  
Phase Separation ◽  
Contact Angles ◽  
Low Ph ◽  
Hydrophobically Modified ◽  
Paper Sizing ◽  
Surface Sizing ◽  
Separation Temperature ◽  
Hydrophobic Nature ◽  
Sizing Agents ◽  
Charge Temperature

The aim of this study was to investigate the properties of hydrophobically modified (HM) quaterna-ry ammonium starch ethers for paper sizing. These starches possess temperature-responsive properties; that is, gelation or phase separation occurs at a certain temperature upon cooling. This insolubility of the HM starches in water at room temperature improved their performance as sizing agents. The contact angles for water on sized liner were substantially larger than on unsized liner. When the application temperature was well above the critical phase-separation temperature, larger contact angles were obtained for liner independently of pH compared with those at the lower application temperature. Cobb60 values for liner decreased upon surface sizing, with a low pH and high application temperature giving lower water penetration. Contact angles on greaseproof paper decreased upon sur-face sizing as compared to unsized greaseproof paper, independently of pH and temperature. Greaseproof paper showed no great difference between unsized substrates and substrates sized with HM starch at different pH. This is probably due to the already hydrophobic nature of greaseproof paper. However, the Cobb60 values increased at low pH and low application temperature. Surfactants were added to investigate how they affect the sized surface. Addition of surfactant reduces the contact angles, in spite of indications of complex formation.

scholarly journals Effect of sizing agent on interfacial properties of carbon fiber-reinforced PMMA composite

2021 ◽  
Vol 30 ◽  
pp. 2633366X2097865
Author(s):  
Li Jian
Keyword(s):  
Shear Strength ◽  
Surface Treatment ◽  
Photoelectron Spectroscopy ◽  
Resin Composite ◽  
Contact Angles ◽  
Static Contact ◽  
Before And After ◽  
C Value ◽  
Interlayer Shear Strength ◽  
Pmma Resin

The surface treatment of carbon fibers (CFs) was carried out using a self-synthesized sizing agent. The effects of sizing agent on the surface of CFs and the interface properties of CF/polymethyl methacrylate (PMMA) composites were mainly studied. Scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and static contact angle were used to compare and study the CFs before and after the surface treatment, including surface morphology, surface chemical element composition, and wettability of the surface. The influence of sizing agent on the mechanical properties of CF/PMMA resin composite interface was investigated. The results show that after sizing treatment, the CF surface O/C value increased by 35.1% and the contact angles of CF and resin decreased by 16.2%. The interfacial shear strength and interlayer shear strength increased by 12.6%.

Bifunctional Composites for Biofilms Modulation on Cervical Restorations

2021 ◽  
pp. 002203452110181
Author(s):  
A.A. Balhaddad ◽  
I.M. Garcia ◽  
L. Mokeem ◽  
M.S. Ibrahim ◽  
F.M. Collares ◽  
...  
Keyword(s):  
Free Energy ◽  
Surface Free Energy ◽  
Contact Angles ◽  
Bacterial Biofilm ◽  
Dental Composite ◽  
Log P ◽  
Rrna Gene ◽  
Cervical Lesions ◽  
Biofilm Growth ◽  
Biofilm Development

Cervical composites treating root carious and noncarious cervical lesions usually extend subgingivally. The subgingival margins of composites present poor plaque control, enhanced biofilm accumulation, and cause gingival irritation. A potential material to restore such lesions should combine agents that interfere with bacterial biofilm development and respond to acidic conditions. Here, we explore the use of new bioresponsive bifunctional dental composites against mature microcosm biofilms derived from subgingival plaque samples. The designed formulations contain 2 bioactive agents: dimethylaminohexadecyl methacrylate (DMAHDM) at 3 to 5 wt.% and 20 wt.% nanosized amorphous calcium phosphate (NACP) in a base resin. Composites with no DMAHDM and NACP were used as controls. The newly formulated 5% DMAHDM–20% NACP composite was analyzed by micro-Raman spectroscopy and transmission electron microscopy. The wettability and surface-free energy were also assessed. The inhibitory effect on the in vitro biofilm growth and the 16S rRNA gene sequencing of survival bacterial colonies derived from the composites were analyzed. Whole-biofilm metabolic activity, polysaccharide production, and live/dead images of the biofilm grown over the composites complement the microbiological assays. Overall, the designed formulations had higher contact angles with water and lower surface-free energy compared to the commercial control. The DMAHDM-NACP composites significantly inhibited the growth of total microorganisms, Porphyromonas gingivalis, Prevotella intermedia/nigrescens, Aggregatibacter actinomycetemcomitans, and Fusobacterium nucleatum by 3 to 5-log ( P < 0.001). For the colony isolates from control composites, the composition was typically dominated by the genera Veillonella, Fusobacterium, Streptococcus, Eikenella, and Leptotrichia, while Fusobacterium and Veillonella dominated the 5% DMAHDM–20% NACP composites. The DMAHDM-NACP composites contributed to over 80% of reduction in metabolic and polysaccharide activity. The suppression effect on plaque biofilms suggested that DMAHDM-NACP composites might be used as a bioactive material for cervical restorations. These results may propose an exciting path to prevent biofilm growth and improve dental composite restorations’ life span.

scholarly journals The Effect of Hydroxyl on the Superhydrophobicity of Dodecyl Methacrylate (LMA) Coated Fabrics through Simple Dipping-Plasma Crosslinked Method

Coatings ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1263
Author(s):  
Liyun Xu ◽  
Yu Zhang ◽  
Ying Guo ◽  
Ruiyun Zhang ◽  
Jianjun Shi ◽  
...  
Keyword(s):  
Thermoplastic Polyurethane ◽  
Hydrophobic Effect ◽  
Surface Hydrophobicity ◽  
Contact Angles ◽  
Binding Property ◽  
Interesting Phenomenon ◽  
Water Contact ◽  
Capacitively Coupled ◽  
Pet Fabric ◽  
Dodecyl Methacrylate

In order to obtain stable superhydrophobicity, suitable hydrophobic treatment agents should be selected according to different material properties. In this paper, cotton and poly(ethylene terephthalate) (PET) fabrics were respectively coated with dodecyl methacrylate (LMA) via argon combined capacitively coupled plasma (CCP), and the surface hydrophobicity and durability of the treated cotton and polyester fabrics are also discussed. An interesting phenomenon happened, whereby the LMA-coated cotton fabric (Cotton-g-LMA) had better water repelling and mechanical durability properties than LMA-coated PET fabric (PET-g-LMA), and LMA-coated hydroxyl-grafted PET fabrics (PET fabrics were successively coated with polyethylene glycol (PEG) and LMA, PET-g-PEG & LMA) had a similar performance to cotton fabrics. The water contact angles of Cotton-g-LMA, PET-g-LMA and PET-g-PEG & LMA were 156°, 153° and 155°, respectively, and after 45 washing cycles or 1000 rubbing cycles, the corresponding water contact angles decreased to 145°, 88°, 134° and 146°, 127° and 143°, respectively. Additionally, thermoplastic polyurethane (TPU) and polyamides-6 (PA6) fabrics all exhibited the same properties as the PET fabric. Therefore, the grafting of hydroxyl can improve the hydrophobic effect of LMA coating and the binding property between LMA and fabrics effectively, without changing the wearing comfort.

scholarly journals Study on contact angles and surface energy of MXene films

RSC Advances ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 5512-5520
Author(s):  
Hang Zhou ◽  
Fuqiang Wang ◽  
Yuwei Wang ◽  
Changping Li ◽  
Changrui Shi ◽  
...  
Keyword(s):  
Surface Energy ◽  
Contact Angles ◽  
Time Dependent ◽  
Wetting Behaviors

This work sheds light on the process- and time-dependent wetting behaviors and surface energy of MXene films.

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