Control Of Surface Energy Research Articles

Interlayer surface energy control for high-efficiency printed organic photovoltaic cells

Incorporating NiO nanoparticles into PEDOT controls the surface energy of interface layer, enabling the manipulation of film formation kinetics and morphology of active layer. Consequently, 1.03 cm2 cells achieved 18.5% efficiency.

Ag-Doped Free-Standing 2D TiO2 Sheets: Electronic, Optical, Magnetic, and Self-Healing Behaviour.

Beyond a critical doping level, Ag - 2D TiO2 sheets (ATO) are deemed to be a flexible transparent conductor, useful for visible-range functional photonic/optoelectronic devices/sensors, sunlight-sensitive catalysis, and light-activated resistive switching. Due to the lack of control of surface energy which often leads to the formation of structural defects and even dimensionality crossover (2D to 0D) of materials during doping reaction, it is challenging to obtain ATO with a controlled doping level. Gauging the urgency, therefore we report the surface energy-controlled synthesis of ATO employing liquid phase exfoliation of TiO2 and subsequent hydrothermal Ag-doping in the presence of Hexamethylenetetramine (HMTA). Electron microscopy and atomic force microscopy reveal ATO sheets with large lateral dimensions. 6-fold, 4-fold, and strain-mediated crystallographic phases of 2D ATO have been revealed by high-resolution electron imaging. Successful tuning of the band gap down to ~ 2 eV with Ag doping up to ~ 10% is obtained. Synthesized 2D ATO have been investigated for their electrical, optical, optoelectronic, photoluminescence, and ferromagnetic behaviour. Visible light-sensitive thermally/structurally robust semiconductor/conductor via tuneable doping will pave the way for their flexible as well as wearable device applications. Self-healing effect of AFM tip-generated mechanical stress has also been demonstrated.

A highly efficient synthetic strategy for de novo NP encapsulation into metal-organic frameworks: enabling further modulated control of catalytic properties.

De novo encapsulation is a prevalent method to prepare composite materials where the structure-tunable metal nanoparticles (NPs) are holistically coated with metal-organic frameworks (MOFs). This method has been demonstrated to have promise in various fields but the extensive application of this approach is still challenging. This study proposed, for the first time, leveraging a specific surface-energy-dominated (SED) mechanism to achieve a highly efficient synthetic strategy for de novo NP encapsulation. The generality of this strategy is proved in applying to various MOFs, reaction conditions and the use of capping agents. By applying the strategy, Pd NPs with different morphologies are encapsulated in UiO-67, which is prone to self-assembly without coating, and an interesting enhancement is investigated in the selective semihydrogenation of alkynes on different Pd surfaces. These results demonstrate that the control of surface energy is a feasible method for efficient NP encapsulation which sheds light on the rational design of MOF-based composites for future applications.

Underestimation of the impact of land cover change on the biophysical environment of the Arctic and boreal region of North America

The Arctic and Boreal Region (ABR) is subject to extensive land cover change (LCC) due to elements such as wildfire, permafrost thaw, and shrubification. The natural and anthropogenic ecosystem transitions (i.e. LCC) alter key ecosystem characteristics including land surface temperature (LST), albedo, and evapotranspiration (ET). These biophysical variables are important in controlling surface energy balance, water exchange, and carbon uptake which are important factors influencing the warming trend over the ABR. However, to what extent these variables are sensitive to various LCC in heterogeneous systems such as ABR is still an open question. In this study, we use a novel data-driven approach based on high-resolution land cover data (2003 and 2013) over four million km2 to estimate the impact of multiple types of ecosystem transitions on LST, albedo, and ET. We also disentangle the contribution of LCC vs. natural variability of the system in changes in biophysical variables. Our results indicate that from 2003 to 2013 about 46% (∼2 million km2) of the region experienced LCC, which drove measurable changes to the biophysical environment across ABR over the study period. In almost half of the cases, LCC imposes a change in biophysical variables against the natural variability of the system. For example, in ∼35% of cases, natural variability led to −1.4 ± 0.9 K annual LST reduction, while LCC resulted in a 0.9 ± 0.6 K LST increase, which dampened the decrease in LST due to natural variability. In some cases, the impact of LCC was strong enough to reverse the sign of the overall change. Our results further demonstrate the contrasting sensitivity of biophysical variables to specific LCC. For instance, conversion of sparsely vegetated land to a shrub (i.e. shrubification) significantly decreased annual LST (−2.2 ± 0.1 K); whereas sparsely vegetated land to bare ground increased annual LST (1.6 ± 0.06 K). We additionally highlight the interplay between albedo and ET in driving changes in annual and seasonal LST. Whether our findings are generalizable to the spatial and temporal domain outside of our data used here is unknown, but merits future research due to the importance of the interactions between LCC and biophysical variables.

Controlling the Surface Modification by CF4 Plasma Treatment for Inkjet Printed Color Conversion Layer With InP‐Based QDs Ink

AbstractControlling of thickness profile in micro‐scale pixels via an inkjet printing process remains a challenge and strict control of surface energy is required. Herein, the surface energy of each substrate is controlled by using CF4 plasma treatment (CPT) to control thickness profile and improve color conversion efficiency (CCE) of the inkjet printed quantum dots (QDs) color conversion layer (CCL). The bank surface becomes hydrophobic due to the fluorination, while the glass becomes hydrophilic due to the cleaning effect by the CPT. Through a systemic investigation of the polar and non‐polar components of the surface energy, it is found that the ink behavior of inkjet‐printed QDs in the pixels is closely related to the non‐polar component of the surface energy. In addition, it is found that more rigorous control of the surface is required for array printing and a wide range of thickness profile control is possible by CPT. The thickness increases by up to 10 µm, the blue leakage is reduced by 26.38%, and the CCE increases by a maximum of 5.71% depending on the CPT. As a result, the relationship between the thickness profile of the CCL and CCE is confirmed through the fabrication of QD‐organic light emitting diodes.

Patternization of cathode metal using low surface energy organic molecules in OLED thermal evaporation process

Facile cathode metal patterning is immensely vital these days as sensor embedded or transparent OLED device applications. In this study, we report a self-metal patterning method by controlling the surface energy of beneath layer and metal thermal deposition temperature in the patterning layer/metal structure in OLED evaporation process. In order to realize the self-metal patterning, a metal patterning layer (MPL) was introduced before the metal deposition which has the property of inhibition of metal deposition by the control of surface energy. Among several MPLs, a low surface energy material of CBP (4,4′-bis(N-carbazolyl)-1,1′-biphenyl) shows a good self-metal patterning of low deposition temperature Mg metal. Whereas, the lowest surface energy materials of PFTC (polyfluoro-tetracosane) results in excellent patterning properties in both Mg as well as high source evaporation temperature metal Ag. Our self-metal patterning technology could be very useful for upcoming numerous electronic applications.

Laser Processing of Polymers for Surface Energy Control of Biomedical Implants

Poly (etheretherketone) (PEEK) is a high-performance rigid polymer that combines excellent chemical resistance, mechanical strength, and dimensional stability. PEEK is mostly used in the biomedical field for the manufacture of implants. However, the inherently bioinert PEEK surface poses a challenge in terms of adhesion at the implant-tissue interface. Effective enhancement of the adhesive properties of PEEK can be achieved by modifications of surface wettability and free energy. Although many studies investigate the influence of laser parameters on wettability and topography of PEEK, there is scarce information in literature on surface treatment with CO2 laser of neat PEEK. Furthermore, there is no detailed literature report on impact of various laser parameters on the biomechanical properties of PEEK relevant for implants. Therefore, this work focuses on enhancing surface functionality of PEEK through surface energy control. Samples treated at various laser power, fluence, beam pitch and number of passes were characterized with 3D profilometry, Rockwell hardness test, compression tests and contact-angle measurements. Generally, CO2 laser treatment of PEEK did not result in unfavorable changes in its bulk mechanical properties, namely, yield strength and elastic modulus only above the ablation threshold. At a fluence of 14 J/cm2, a significant reduction in hardness (98.03 HRM) was recorded with a single-pass processing. A positive correlation was observed between roughness parameters, groove geometries and laser fluence. More intense surface changes were achieved via ablative mechanism with single-pass processes at a lower total fluence in comparison to double-pass ones. Overall, all increases in roughness resulting from non-ablative processes led to improved wettability.

Kinetics-controlled regulation for homogeneous nucleation and growth of colloidal polymer and carbon nanospheres.

Size regulation of uniform polymer nanospheres (PNSs) and carbon nanospheres (CNSs) below 100 nm has been difficult and is limited by multiple factors, such as ongoing nucleation, Ostwald ripening, minimization of surface energy, and high viscosity during the nucleation and growth process. In this study, a kinetics-controlled regulation is reported for the synthesis of monodispersed PNSs and corresponding CNSs with adjustable size below 100 nm. During the synthesis of PNSs, three distinct stages including surface energy control, surface tension control and viscosity control have been observed, where the concentration of block copolymer F127 (CF127) plays a vital role in affecting the nucleation rate of PNSs and tunes the diffusion rate of monomers and migration of particles during the nucleation and growth process. As a consequence, the size of monodisperse CNSs can be customized from 100 nm down to 41 nm with PDI below 5%.

Optimization of the Rework of Bended OLED Displays by Surface-Energy Control

Recent display technology has changed substantially from flat-type displays to bended displays. As a result, the lamination process for bonding the panel substrates and bended window glass has become difficult due to the changes in display shape, and the use of optically clear adhesive (OCA) makes it impossible to rework defective substrates due to residue problems. Therefore, it is necessary to research and develop a substrate-surface treatment that maintains the initial adhesion and is reusable via the complete removal of impurities during delamination in order to enable rework. In this paper, the possibility of maintaining adhesive force and reusing substrates was confirmed through the surface treatment of substrates and OCA using various materials. We found that a surface coating and a cooling treatment of additional substrates completely removed the impurities that remained on the substrates during reworking. These results could contribute to improving lamination-process technology and the productivity of the various forms of next-generation displays that are currently under development.

Application of hydrophobic coating to reduce leakage current through surface energy control of high voltage insulator

A hydrophobic coating was applied using atmospheric-pressure plasma to solve the problem of leakage current caused by the attachment of pollutants to transmission line ceramic insulators. After applying coatings on quartz and ceramic substrates using HMDS:N, C4F8, anti-fingerprint, and CH4 materials, hydrophobicity was determined through water contact angle analysis. In the case of ceramic substrates, the AFM analysis results show that the value of roughness, Ra, determined by the contact angle according to Wenzel's law, of the surface was 63.1–76.4 nm. As a result of XPS and FT-IR analyses, hydrophobic characteristics were observed when C-H bonding was large and Si-O bonding and oxygen content were small. The finite element method analysis shows that when a hydrophobic coating material possessing a high contact angle is used, the adhesion density of contaminants with conductivity is lower than that of a ceramic insulator with hydrophilicity. This reduces the leakage current. It is difficult to artificially clean an insulator in the installation environment, and fewer pollutants will attach to a hydrophobic surface because of rain, snow, or wind in the natural environment.

Reduced Biofilm Formation at the Air-Liquid-Solid Interface via Introduction of Surfactants.

Reduced biofilm formation is highly desirable in applications ranging from transportation to separations and healthcare. Biofilms often form at the three-phase interface where air, liquid, and solid coexist due to the close proximity to nutrients and oxygen. Reducing biofilm formation at the triple interface presents challenges because of the conflicting requirements for hydrophobicity at the air-solid interface (for self-cleaning properties) and for hydrophilicity at the liquid-solid interface (for reduced foulant adhesion). Meeting those needs simultaneously likely entails a dynamic surface, capable of shifting the surface energy landscape in response to wetting conditions and thus enabling hydrophobicity in air and hydrophilicity in water. Here, we designed a facile approach to render existing surfaces resistant to biofilm formation at the triple interface. By adding trace amounts (∼0.1 mM) of surfactants, biofilm formation of Pseudomonas aeruginosa (known to form biofilm at the triple interface) was reduced on all surfaces tested, ranging from hydrophilic to hydrophobic, polar to nonpolar. That reduced fouling was not a result of the known antimicrobial effects. Instead, it was attributed to the surface-adsorbed surfactants that dynamically control surface energy at the triple interface. To further understand the effect of surfactant-surface interactions on biofilm reduction, we systematically varied the surfactant charge type and surface properties (surface energy and charge). Electrostatic interactions between surfactants and surfaces were identified as an influential factor when predicting the relative fouling reduction upon introduction of surfactants. Nevertheless, biofilm formation was reduced even on the charge-neutral, fluorinated surface made of poly(1H, 1H, 2H, 2H-perfluorodecyl acrylate) by more than 2-fold simply via adding 0.2 mM dodecyl trimethylammonium chloride or 0.3 mM sodium dodecyl sulfate. Given its robustness, this strategy is broadly applicable for reducing fouling on existing surfaces, which in turn improves the cost-effectiveness of membrane separations and mitigates contaminations and nosocomial infections in healthcare.

Engineering the Microstructure and Morphology of Explosive Films via Control of Interfacial Energy.

Physical vapor deposition of organic explosives enables growth of polycrystalline films with a unique microstructure and morphology compared to the bulk material. This study demonstrates the ability to control crystal orientation and porosity in pentaerythritol tetranitrate films by varying the interfacial energy between the substrate and the vapor-deposited explosive. Variation in density, porosity, surface roughness, and optical properties is achieved in the explosive film, with significant implications for initiation sensitivity and detonation performance of the explosive material. Various surface science techniques, including angle-resolved X-ray photoelectron spectroscopy and multiliquid contact angle analysis, are utilized to characterize interfacial characteristics between the substrate and explosive film. Optical microscopy and scanning electron microscopy of pentaerythritol tetranitrate surfaces and fracture cross sections illustrate the difference in morphology evolution and the microstructure achieved through surface energy modification. X-ray diffraction studies with the Tilt-A-Whirl three-dimensional pole figure rendering and texture analysis software suite reveal that high surface energy substrates result in a preferred (110) out-of-plane orientation of pentaerythritol tetranitrate crystallites and denser films. Low surface energy substrates create more randomly textured pentaerythritol tetranitrate and lead to nanoscale porosity and lower density films. This work furthers the scientific basis for interfacial engineering of polycrystalline organic explosive films through control of surface energy, enabling future study of dynamic and reactive detonative phenomena at the microscale. Results of this study also have potential applications to active pharmaceutical ingredients, stimuli-responsive polymer films, organic thin film transistors, and other areas.

Chemical treatment of Ag paste electrodes for surface energy control

Though various metal powders are used as the main components of conductive pastes, silver is most widely used owing to its high conductivity and strong corrosion resistance. Hence, silver paste is required for the manufacturing of many items, such as large-area display panels and semiconductor chips. However, electrodes made of silver paste commonly have low surface energy levels, resulting in hydrophobicity. To strengthen the adhesive force between films when silver paste is used as a component in items consisting of many film layers, the silver paste must have high surface energy. In other words, it must show low contact angles in water-drop measurements. Despite the proposal and practicality of the plasma treatment method, this method can cause radical damage, and it is undesirable for batch processes. In this study, the surface energy of a silver paste electrode was changed by dipping it into a sulfuric acid solution. A simple but effective controllable method by which to manage the surface energy is demonstrated, which may be useful for the selective control of specific films on large-area substrates in the future.

Preparation and Properties of Superhydrophobic Surface of Conducting Polymer Based on Linking Reaction

Superhydrophobic Surfaces Have Great Application Value in the Fields of Self-Cleaning, Corrosion Resistance, Fluid Drag Reduction, Ice Resistance and the Like, While Superhydrophobic Surfaces with Transparency, Conductivity or Other Functions Have Larger Application Space. the Appearance of the Lotus Leaf Has a Self-Cleaning Function, and the Most Typical Example is the Lotus Leaf Surface Which is out of Silt But Not Imbrued. through the Research and Analysis of Superhydrophobic Phenomena in Nature, the Low Surface Energy Substances on Superhydrophobic Surfaces and the Micro-Nano Scale Hierarchical Structure Are Considered as the Two Decisive Factors for Forming Superhydrophobic. the Classical Theory of Surface Wettability Indicates That the Wettability of Liquid Depends on the Surface Energy and Surface Roughness. Various Methods Have Been Developed for the Preparation of Superhydrophobic Surfaces with Conducting Polymers. by Selecting Materials with Appropriate Surface Energy and Fine Control of Surface Structure, Various Surface Functionalization Can Be Realized.

Surface-Energy Control and Characterization of Nanoparticle Coatings

Accurate and reproducible measurement of the structure and properties of high-value nanoparticles is extremely important for their commercialization. A significant proportion of engineered nanopart...

Direct transfer of graphene by control of polydimethylsiloxane surface energy

In this study, graphene direct transfer patterning was investigated by using plasma surface modification of polydimethylsiloxane (PDMS) with inductively coupled C4F8/O2/Ar gas mixture plasma. The spin-coated graphene on the PDMS was directly transferred to a polyethylene terephthalate (PET) substrate. Direct transfer characteristics were analyzed using the film's properties such as the contact angle, and sheet resistance, and the degree of adhesion between the PDMS and graphene. Further analysis was performed on results obtained via transmission electron microscopy (TEM), and Raman spectroscopy. As the O2 gas ratio in the C4F8/O2/Ar plasma increased, the contact angle at the PDMS surface decreased. This indicates that the PDMS surface changes from hydrophobic to hydrophilic because of the plasma treatment. As-grown graphene films exhibited D, G, and 2D-peaks in their Raman spectra, and post-annealing was used to reduce or eliminate the D-peak. The direct transfer of graphene from PDMS to the PET substrate occurred at an O2 gas ratio that was above 50%. TEM and Raman mapping were used for the evaluation of the direct transfer characteristics. The adhesion between the PDMS and the coated graphene was calculated to confirm the direct transfer mechanism. The adhesion decreased as a consequence of the C4F8/O2/Ar plasma treatment, while the graphene direct transfer characteristics to the PET substrate were, in turn, improved. Therefore, an important indicator of the efficiency of the direct transfer of graphene is the degree of adhesion between the graphene and the PDMS. The touch sensor was fabricated using the directly transferred graphene thin film and an indium tin oxide (ITO) transparent electrode. The mutual capacitance value, which is characteristic of the touch sensor, confirmed the mutual capacitance value similar to that of the existing ITO.

Control of dielectric surface energy by dry surface treatment for high performance organic thin film transistor based on dibenzothiopheno[6,5-b:6′,5′-f]thieno[3,2-b]thiophene semiconductor

We studied organic thin film transistors using vacuum-deposited para-sexiphenyl (p-6P) as a sublayer to reduce the surface energy of the dielectric material. The correlation between the growth mode of a thin film of the organic semiconductor dibenzothiopheno[6,5-b:6′,5′-f]thieno[3,2-b]thiophene and the number of p-6P sublayers could be explained by a surface energy difference resulting from molecular orientation changes in the p-6P layer. A local surface energy difference was confirmed by measuring the adhesion force using a nanomechanical force measurement method.

The influence of dopants on the surface enthalpy of Yttrium aluminum garnet (YAG)

Surface enthalpy is an important parameter to predict the phase stability of crystalline materials at the nanoscale, having parametric influence in processes such as coarsening and single crystal nucleation and growth. Yttrium aluminum garnet (Y3Al5O12, YAG) is a base material for solid state laser, with limited thermodynamic information on interfacial energies available. In the present study, we experimentally determined the surface enthalpy of YAG by using microcalorimetry. Nanoparticles were used to maximize the respective measurable heat effect exploiting their intrinsically high surface areas. We further tracked the effect of La or Mg as dopants on the surface enthalpy of YAG. The results indicate that there is a slight reduction in the surface enthalpy of YAG nanoparticles after doping with 2 mol%-La or Mg. The anhydrous surface enthalpy of undoped YAG was measured as 1.28 ± 0.11 J/m2 and was reduced to 0.98 ± 0.09 and 1.11 + 0.07 J/m2 for 2 mol%-La, and Mg doped YAG nanoparticles, respectively, confirming anhydrous surface energies of YAG can be modified by dopants. The effect of water adsorption on the energies, however, show that the differences between doped and undoped YAG surface energies become negligible at relative pressures as low as 20%, challenging surface energy control as a viable process optimization parameter in the presence of humidity.

Texture dependent surface energy measurements on magnetostrictive alloys for abnormal grain growth modeling

Galfenol is a magnetostrictive alloy used in sensing, actuating, and energy harvesting devices. Developing protocols for making thin sheet Galfenol with abnormally grown Goss or Cube grains is challenging because the mechanisms that regulate grain boundary mobility and texture development in these alloys are not well understood. Grain boundary energy models do not account for extraneous driving forces caused by the control of surface energy from atmospheric annealing conditions. By characterizing the surface energy of specific Galfenol grains at room temperature, we can develop a more accurate thermodynamic-based framework for modeling abnormal grain growth and texture development. This will be used to understand why a high temperature atmospheric anneal under 0.5%H2S in Ar transforms myriad grains into highly textured, single-crystal-like polycrystalline material while pure Ar does not. To experimentally measure surface energy, we have developed a non-destructive process to directly probe highly-textured and single-crystal Galfenol. The process involves high quality polishing to sub-nanometer roughness, Ar plasma cleaning to remove native oxides, and preserving the bare metal surface by immersion in hydrocarbon liquid. In this bulk hydrocarbon liquid, we use the two-liquid-phase contact angle method to measure surface energy. Experimental surface energy values on single crystals agree with DFT calculations, confirming the validity of this process. We use this method to observe a decrease in surface energy for sulfur contaminated Galfenol.

Biomimetic magnetic-responsive cilia-like soft device: surface energy control and external field actuation

Many natural systems that are capable of self-regulated, autonomous controlling their shapes, generally match or even exceed the performance of rigid robotic systems. Currently, designing biomimetic soft devices by mimicking the natural intelligence with tunable ability still remains a grand challenge. Herein, we demonstrate a novel biomimetic cilia-like soft device using the magnetic feedback of microrod arrays. Such cilia-like microrod arrays are fabricated by distributing Co nanoparticles into silicon-based polymer. The critical aspect ratio of the microrod arrays can reach 48.7, which is 5.4-times higher than original 9.1 through considerably reducing its surface energy. This large increase in critical aspect ratio will endow the microrods an excellent durability and ensure the posture recovery during the magnate-responsive actuation. Meanwhile, magnetic-responsive Co nanoparticles are aligned and concentrated in the top of each microrod, which leads to the differentiated elastic modulus and ultimate strength along the length. Thereby, as the magnetic field intensity increases, the microrod arrays autonomously perform correspondingly reversible bending deformation without collapse, successfully achieving remotely controlled magnetic actuation. Therefore, this work opens up a new avenue towards soft, autonomous smart devices.