Four types of contact angles (receding, most stable, advancing, and “static”) were measured by two independent laboratories for a large number of solid surfaces, spanning a large range of surface ...tensions. It is shown that the most stable contact angle, which is theoretically required for calculating the Young contact angle, is a practical, useful tool for wettability characterization of solid surfaces. In addition, it is shown that the experimentally measured most stable contact angle may not always be approximated by an average angle calculated from the advancing and receding contact angles. The “static” CA is shown in many cases to be very different from the most stable one. The measured contact angles were used for calculating the surface tensions of the solid samples by five methods. Meaningful differences exist among the surface tensions calculated using four previously known methods (Owens-Wendt, Wu, acid−base, and equation of state). A recently developed, Gibbsian-based correlation between interfacial tensions and individual surface tensions was used to calculate the surface tensions of the solid surfaces from the most stable contact angle of water. This calculation yielded in most cases higher values than calculated with the other four methods. On the basis of some low surface energy samples, the higher values appear to be justified.
Self-assembled monolayers (SAMs) of galactoside-terminated alkanethiols have protein-resistance properties which can be tuned via the degree of methylation Langmuir 2005, 21, 2971–2980. Specifically, ...a partially methylated compound was more resistant to nonspecific protein adsorption than the hydroxylated or fully methylated counterparts. We investigate whether this also holds true for resistance to the attachment and adhesion of a range of marine species, in order to clarify to what extent resistance to protein adsorption correlates with the more complex adhesion of fouling organisms. The partially methylated galactoside-terminated SAM was further compared to a mixed monolayer of ω-substituted methyl- and hydroxyl-terminated alkanethiols with wetting properties and surface ratio of hydroxyl to methyl groups matching that of the galactoside. The settlement (initial attachment) and adhesion strength of four model marine fouling organisms were investigated, representing both micro- and macrofoulers; two bacteria (Cobetia marina and Marinobacter hydrocarbonoclasticus), barnacle cypris larvae (Balanus amphitrite), and algal zoospores (Ulva linza). The minimum in protein adsorption onto the partially methylated galactoside surface was partly reproduced in the marine fouling assays, providing some support for a relationship between protein resistance and adhesion of marine fouling organisms. The mixed alkanethiol SAM, which was matched in wettability to the partially methylated galactoside SAM, consistently showed higher settlement (initial attachment) of test organisms than the galactoside, implying that both wettability and surface chemistry are insufficient to explain differences in fouling resistance. We suggest that differences in the structure of interfacial water may explain the variation in adhesion to these SAMs.
Plasma-assisted chemical vapour deposition (PACVD) siloxane coatings from a mixture of hexamethyldisiloxane (HMDSO) and O
2, and hybrid coatings deposited by simultaneous sputtering of silicon and ...plasma polymerisation of HMDSO
+
O
2 were prepared on glass and steel substrates. The effect of the addition of sputtered silicon was investigated for coatings with different HMDSO/O
2 ratios. The microstructure and composition of coatings were affected by the coating parameters used. Silicon content was roughly the same for all coatings; carbon content decreased while oxygen content and surface energy increased with decreasing HMDSO/O
2 ratio in hybrid coatings. Hardness and modulus were higher for hybrid coatings and increased with decreasing HMDSO/O
2 ratio. Hybrid coatings showed much better scratch and wear resistance than PACVD coatings. All coatings showed good fouling-release performance with the freshwater bacterium
Pseudomonas fluorescens.
A range of SiO
x
-like coatings was deposited on glass slides from a hexamethylsiloxane precursor by plasma-assisted CVD. The effect of varying deposition parameters, specifically ion cleaning time ...and HMDSO/O
2 ratios, on the coating properties and antifouling performance was investigated. At low HMDSO/O
2 ratios, the resulting coatings were close to SiO
2. Carbon content in the bulk of the coatings increased with increasing HMDSO/O
2 ratio. Coatings deposited at high HMDSO/O
2 ratios and with the longest cleaning time (30
min), elevated the relative carbon content to 25 atomic %. Surface energies (22–43
mJ/m) were correlated with the degree of surface oxidation and hydrocarbon content. With the exception of the most polar coatings the apolar component of the surface energy (
γ
LW) was the dominant component. In the most hydrophilic coatings, the Lewis base component of the surface energy (
γ
−) was dominant. Significantly improved antifouling performance was detected with the most reduced coatings deposited using the extended ion cleaning times. For both, the removal of sporelings of the marine green alga,
Ulva
linza and the initial adhesion of the freshwater bacterium,
Pseudomonas fluorescens, there was a strong, positive correlation between strength of attachment and ion cleaning time. Increased ion cleaning time will elevate the deposition temperature, increasing decomposition rates and thus the crosslinking of the polymer. Increased cross-linking may render these coatings less permeable to penetration and mechanical interlocking by the adhesive polymers used by these organisms, thus reducing their adhesion. Films with improved biological performance have potential for use as coatings in the control of biofouling in applications such as heat exchangers, where thin films are important for effective thermal transfer, or optical windows where transparency is important.
A range of titanium doped diamond-like carbon (Ti-DLC) coatings with different Ti contents were prepared on stainless steel substrates using a plasma-enhanced chemical vapour deposition technique. It ...was found that both the electron donor surface energy and the surface roughness of the Ti-DLC coatings increased with increasing Ti contents in the coatings. Bacterial adhesion to the coatings was evaluated against Escherichia coli WT F1693 and Pseudomonas aeruginosa ATCC 33347. The experimental data showed that bacterial adhesion decreased with the increases of the Ti content, the electron donor surface energy and surface roughness of the coatings, while the bacterial removal percentage increased with the increases of these parameters. The Ti-DLC coatings reduced bacterial attachment by up to 75% and increased bacterial detachment from 15 to 45%, compared with stainless steel control.
Si- and N-doped diamond-like carbon (DLC) coatings with various Si and N contents were deposited on glass slides using magnetron sputter ion-plating and plasma-enhanced chemical vapour deposition. ...Surface energy analysis of the DLC coatings revealed that with increasing Si content, the electron acceptor
value decreased while the electron donor
value increased. The antifouling property of DLC coatings was evaluated with the bacterium, Pseudomonas fluorescens, which is one of the most common microorganisms forming biofilms on the surface of heat exchangers in cooling water systems. P. fluorescens had a high value of the
component (69.78 mN m
−1
) and a low value of the
component (5.97 mN m
−1
), and would be negatively charged with the zeta potential of −16.1 mV. The experimental results showed that bacterial removal by a standardised washing procedure increased significantly with increasing electron donor
values and with decreasing electron acceptor
values of DLC coatings. The incorporation of 2%N into the Si-doped DLC coatings further significantly reduced bacterial attachment and significantly increased ease of removal. The best Si-N-doped DLC coatings reduced bacterial attachment by 58% and increased removal by 41%, compared with a silicone coating, Silastic® T2. Bacterial adhesion strength on the DLC coatings is explained in terms of thermodynamic work of adhesion.
The rapid development of the global offshore industry and of amphibious chemical, steel and power plants leads to more intensive use of natural water resources (sea, river and lake water) as a ...cooling medium. However, heat exchangers using the water as a coolant suffer from biofouling problem, which reduces heat transfer performance significantly. The cost of cleaning and lost output can be extremely high. The high incidence of infections caused by the biofilm formation on the surfaces of medical devices and implants, including catheters and bone fracture fixation pins etc. has a severe impact on human health and health care costs. An approach to reduce biofouling or infection rate is the application of a range of different coatings to the surfaces of equipment. So far the most promising coatings include Ni–P–PTFE coatings and modified diamond like carbon (DLC) coatings etc. However these coatings need to be futher improved and optimised in order to get the best anti-biofouling performance. In this study, a range of novel Ni–P–PTFE-biocide polymer nanocomposite coatings and modified DLC coatings with B, F, N, Si and Ti were designed and produced using electroless plating, magnetron sputter ion-plating and plasma enhanced chemical vapour deposition techniques. The surface properties of the coatings were characterized using surface analysis facilities, including AFM, EDX, OCA-20, SEM and XPS. These nano-composite coatings and nano-structured surfaces were evaluated with bacterial strains that frequently cause heat exchanger biofouling or medical devices-related infections. The experimental results showed that new Ni–P–PTFE-biocide polymer nanocomposite coatings reduced bacterial adhesion by 70% and 94% respectively, compared with Ni–P–PTFE and stainless steel. The experimental results showed that both type and content of the doped elements in DLC coatings had significant influence on bacterial adhesion. The new doped DLC coatings, including Si-N-DLC, F-DLC, B-DLC and Ti-DLC coatings as well as new SiOx-like coatings reduced bacterial adhesion by 60-90% compared with pure DLC and stainless steel. B and Ti-doped DLC coatings also reduced residual protein adhesion by 88-95% compared with pure DLC coatings and stainless steel. In general bacterial adhesion decreased with decreasing total surface energy or with increasing ?- surface energy of the coatings. The bacterial adhesion mechanism of the coatings was explained with extended DLVO theory.
The rapid development of the global offshore industry and of amphibious chemical, steel and power plants leads to more intensive use of natural water resources (sea, river and lake water) as a ...cooling medium. However, heat exchangers using the water as a coolant suffer from biofouling problem, which reduces heat transfer performance significantly. The cost of cleaning and lost output can be extremely high. The high incidence of infections caused by the biofilm formation on the surfaces of medical devices and implants, including catheters and bone fracture fixation pins etc. has a severe impact on human health and health care costs. An approach to reduce biofouling or infection rate is the application of a range of different coatings to the surfaces of equipment. So far the most promising coatings include Ni–P–PTFE coatings and modified diamond like carbon (DLC) coatings etc. However these coatings need to be futher improved and optimised in order to get the best anti-biofouling performance. In this study, a range of novel Ni–P–PTFE-biocide polymer nanocomposite coatings and modified DLC coatings with B, F, N, Si and Ti were designed and produced using electroless plating, magnetron sputter ion-plating and plasma enhanced chemical vapour deposition techniques. The surface properties of the coatings were characterized using surface analysis facilities, including AFM, EDX, OCA-20, SEM and XPS. These nano-composite coatings and nano-structured surfaces were evaluated with bacterial strains that frequently cause heat exchanger biofouling or medical devices-related infections. The experimental results showed that new Ni–P–PTFE-biocide polymer nanocomposite coatings reduced bacterial adhesion by 70% and 94% respectively, compared with Ni–P–PTFE and stainless steel. The experimental results showed that both type and content of the doped elements in DLC coatings had significant influence on bacterial adhesion. The new doped DLC coatings, including Si-N-DLC, F-DLC, B-DLC and Ti-DLC coatings as well as new SiOx-like coatings reduced bacterial adhesion by 60-90% compared with pure DLC and stainless steel. B and Ti-doped DLC coatings also reduced residual protein adhesion by 88-95% compared with pure DLC coatings and stainless steel. In general bacterial adhesion decreased with decreasing total surface energy or with increasing ?- surface energy of the coatings. The bacterial adhesion mechanism of the coatings was explained with extended DLVO theory.
Studies of the peripheral nervous system rely on controlled manipulation of neuronal function with pharmacologic and/or optogenetic techniques. Traditional hardware for these purposes can cause ...notable damage to fragile nerve tissues, create irritation at the biotic/abiotic interface, and alter the natural behaviors of animals. Here, we present a wireless, battery-free device that integrates a microscale inorganic light-emitting diode and an ultralow-power microfluidic system with an electrochemical pumping mechanism in a soft platform that can be mounted onto target peripheral nerves for programmed delivery of light and/or pharmacological agents in freely moving animals. Biocompliant designs lead to minimal effects on overall nerve health and function, even with chronic use in vivo. The small size and light weight construction allow for deployment as fully implantable devices in mice. These features create opportunities for studies of the peripheral nervous system outside of the scope of those possible with existing technologies.
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