Contact Angle Of Water Droplet Research Articles

Superhydrophobic Surface Modification of a Co-Ru/SiO2 Catalyst for Enhanced Fischer-Tropsch Synthesis

Commercial silica support pellets were impregnated and calcined to contain cobalt oxide and ruthenium oxide for Fischer-Tropsch synthesis (FTS). The precatalyst pellets were split evenly into two groups, the control precatalyst (c-precat) and silylated precatalyst (s-precat), which were treated with 1H,1H, 2H, 2H-perfluorooctyltriethoxysilane (PFOS) in toluene. The samples of powderized s-precat were superhydrophobic, as determined by the water droplet contact angle (>150°) and sliding angle (<1°). Thermal analysis revealed the PFOS groups to be thermally stable up to 400 °C and temperature programmed reduction (TPR) studies showed that H2 reduction of the cobalt oxide to cobalt was enhanced at lower temperatures relative to the untreated c-precat. The two active catalysts were examined for their FTS performance in a tubular fixed-bed reactor after in situ reduction at 400 °C for 16 h in flowing H2 to give the active catalysts c-cat and s-cat. The FTS runs were performed under identical conditions (255 °C, 2.1 MPa, H2/CO = 2.0, gas hourly space velocity (GHSV) 510 h–1) for 5 days. Each catalyst was examined in three runs (n = 3) and the mean values with error data are reported. S-cat showed a higher selectivity for C5+ products (64 vs. 54%) and lower selectivity for CH4 (11 vs. 17%), CO2 (2 % vs. 4 %), and olefins (8% vs. 15%) than c-cat. S-cat also showed higher CO conversion, at 37% compared to 26%, leading to a 64% increase in the C5+ productivity measured as g C5+ products per g catalyst per hour. An analysis of the temperature differential between the catalyst bed and external furnace temperature showed that s-cat was substantially more active (DTinitial = 29 °C) and stable over the 5-day run (DTfinal = 22 °C), whereas the attenuated activity of c-cat (DTinitial = 16 °C) decayed steadily over 3 days until it was barely active (DTfinal < 5 °C). A post-run surface analysis of s-cat revealed no change in the water contact angle or sliding angle, indicating that the FTS operation did not degrade the PFOS surface treatment.

A dual resin application system for improved bamboo-wood bonding

In this work, a dual resin application system using commercial phenol formaldehyde (PF) resins with different molecular weight (MW) was investigated to improve bonding performance of bamboo and wood composite laminates. Water droplet contact angle was deemed to be unreliable for assessing resin wettability on bamboo due to its unique tissue structure compared with wood. Microscopic observation of the resin penetration showed high MW PF largely remained in the glueline and only entered the lumens of cut or damaged bamboo cells near the bondline. Low MW PF appeared in cell corners of bamboo parenchyma but not lumens. Applying low MW PF to the bamboo and high MW PF to the wood surface separately significantly improved bond shear strength with reduced difference between dry and wet conditions. The dry and wet bond strengths using the new method were enhanced by 36.5 % and 97.4 %, respectively, compared to high MW PF alone. The results suggest that low MW PF can permeate bamboo cell walls and fortify them against swelling and stress on the bamboo-resin interface in wet conditions. Further modifications are required to produce a stronger adhesive than the bamboo tissue to improve wet shear fiber failure rates and develop a viable structural bond qualification test for bamboo and bamboo-wood composites.

Organic-inorganic hybrid-modified polyester/cotton fabric: Strategy for enhanced flame retardancy, chemical stability and amphiphobicity

As surface treatments for the application of functional components to substrates have gained increasing attention, there is a growing interest in endowing fabrics with multiple functionalities in addition to flame retardancy. This study describes the successful formation of a fluorination treatment of Al2O3 cross-linked onto the surface of a self-assembled PEI/PA coating for polyester/cotton (PC) fabrics. This coating approach aims to improve the flame retardancy, amphiphobicity, chemical stability, and self-cleaning properties of PC fabrics. The treated fabrics demonstrated exceptional fire resistance, with a significant reduction of 55.4 % in the peak heat release rate (pHRR) during combustion. Correspondingly, there was a decrease of 53.8 % in the peak release rate of CO2, while the limiting oxygen index increased from 17.9 % to 30.4 %. Additionally, the contact angles of water, glycol, and peanut oil droplets before and after treatment increased from 20.4°, 65.1°, and 34.6° to 146.0°, 143.1°, and 97.9°, respectively. The coating exhibits durable self-cleaning performance in both ambient and hot water and remains stable across a pH range of 1–14. This research offers a viable pathway for achieving flame retardancy on fabrics while enhancing their multifunctionality.

Superhydrophobic quasi-periodic concave microlens array on fused silica prepared by spatially modulated picosecond laser parallel processing

Fused-silica-based microlens array (MLA) has excellent stability in the harsh environment. However, it is still a challenge to efficiently prepare superhydrophobic quasi-periodic MLA and keep the optical performance of the microlens. In this paper, we proposed spatial modulated picosecond laser parallel processing method to prepare a superhydrophobic quasi-periodic MLA on fused silica. By using a spatial light modulator, the picosecond laser was shaped to multi-focal spots and line-shape beam, respectively, which improved the fabrication efficiency. The line-shape beam was the key to induce micro-nanostructures on the smooth MLA and keep the optical performance of the microlens. The results showed that the surface roughness of the microlens region was less than 100 nm. Combing with shaping picosecond laser processing and chemical treatment, the superhydrophobic MLAs showed the excellent anti-fogging and self-cleaning properties. The average contact angle of the superhydrophobic MLAs was 162.3°. The superhydrophobic MLA showed low adhesion to water droplet (<10 μN) and low contact angle hysteresis (2.1° ± 0.7°). We believe shaping picosecond laser parallel processing method is a flexible and low-cost approach to prepare superhydrophobic micro-optical elements on fused silica.

Characterization of hydrophobic metasurfaces fabricated on Ni-Mn-Ga-based alloys using femtosecond pulsed laser ablation

The generation of hydrophobic surfaces through laser ablation has garnered considerable attention, particularly for its prospective diverse applications across various industries. This study explores the possibility of generating controllable hydrophobic metasurfaces on Ni-Mn-Ga-based magnetic shape memory (MSM) alloys using femtosecond pulse width laser (FPWL). While hydrophobic surfaces have been achieved on different materials through a variety of different techniques, the research marks the first systematic attempt to tailor hydrophobicity on the surface of Ni-Mn-Ga-based alloys. By characterizing surfaces treated with different laser parameters, the distinct morphologies and hydrophobic properties corresponding to each surface were identified. This newfound control over surface properties with specific machining parameters opens possibilities for applications in microfluidic devices. Additionally, the potential of utilizing the magnetic-field-induced strain (MFIS) exhibited by Ni-Mn-Ga single crystals to alter surface hydrophobicity was explored. Metasurfaces mimicking the dimensional changes in elongation induced by MFIS demonstrated higher static contact angles (SCAs) for water droplets compared to the original surfaces. This approach presents a promising avenue for creating multifunctional microdevices with controllable hydrophobicity using Ni-Mn-Ga-based alloys. Our findings not only offer insights into tailoring of hydrophobic/hydrophilic properties on Ni-Mn-Ga-based MSM alloys but also provide a novel methodology for fabricating functional metasurfaces on other metals.

Instantaneous fundamental modes and contact angles of droplets from surface atoms

Contact angle measurements of sessile or moving droplets are by far the most common way to characterize their wetting properties. The typical route to obtain contact angle estimates from atomistic molecular dynamics simulations requires the calculation of an isochore or the equimolar dividing surface, both of which need sizeable statistics to achieve acceptable accuracy and are less suitable in non-stationary conditions. Here, we propose an algorithm for estimating the contact angle that relies on the identification of interfacial molecules, which can determine the instantaneous location of the liquid surface. We apply this algorithm to calculate the contact angles of water droplets at equilibrium and out of equilibrium on graphite-like substrates, paying particular attention to modeling the presence of excited modes using general ellipses to fit the droplet surface. The algorithm is implemented in a user-friendly way in the Pytim software package.

Wood sponge with photothermal, magnetically driven, and superhydrophobic characteristics for high-viscosity oil–water separation

In this work, naturally degradable porous balsa wood was used as a raw material to prepare a highly elastic wood sponge (WS) substrate using a two-step chemical method and a freeze-drying method. The surface hydrophobic modification of Fe3O4 nanoparticles using the fluorine-free material octadecyltrimethoxysilane (C18TMS) solved the problem of agglomeration caused by the high nanoparticle surface energy. Polydopamine (PDA), hydrophobically modified Fe3O4 (C18TMS/Fe3O4), and low-surface-energy polydimethylsiloxane (PDMS) were sprayed onto WS substrates using a simple spraying method. An environmentally friendly adsorption sponge with photothermal, magnetically driven, and superhydrophobic properties was prepared for the first time using this method. The prepared sponge had a water droplet contact angle of 156.8° and exhibited excellent oil–water separation performances. Due to the addition of PDA and Fe3O4, the modified sponge exhibited excellent photothermal performance, rapidly heating to 63.4°C under a sunlight intensity of 1 kW m−2. The superhydrophobic WS prepared in this experiment provides a more environmentally friendly and low-cost way for high viscosity oil–water separation and targeted removal of oil pollution.

Kinetics of Surface Wettability of Aromatic Polymers (PET, PS, PEEK, and PPS) upon Treatment with Neutral Oxygen Atoms from Non-Equilibrium Oxygen Plasma.

The wettability of polymers is usually inadequate to ensure the appropriate spreading of polar liquids and thus enable the required adhesion of coatings. A standard ecologically benign method for increasing the polymer wettability is a brief treatment with a non-equilibrium plasma rich in reactive oxygen species and predominantly neutral oxygen atoms in the ground electronic state. The evolution of the surface wettability of selected aromatic polymers was investigated by water droplet contact angles deposited immediately after exposing polymer samples to fluxes of oxygen atoms between 3 × 1020 and 1 × 1023 m-2s-1. The treatment time varied between 0.01 and 1000 s. The wettability evolution versus the O-atom fluence for all aromatic polymers followed similar behavior regardless of the flux of O atoms or the type of polymer. In the range of fluences between approximately 5 × 1020 and 5 × 1023 m-2, the water contact angle decreased exponentially with increasing fluence and dropped to 1/e of the initial value after receiving the fluence close to 5 × 1022 m-2.

Preparation of Hydrophobic Au Catalyst and Application in One-Step Oxidative Esterification of Methacrolein to Methyl Methacrylate.

The water produced during the oxidative esterification reaction occupies the active sites and reduces the activity of the catalyst. In order to reduce the influence of water on the reaction system, a hydrophobic catalyst was prepared for the one-step oxidative esterification of methylacrolein (MAL) and methanol. The catalyst was synthesized by loading the active component Au onto ZnO using the deposition-precipitation method, followed by constructing the silicon shell on Au/ZnO using tetraethoxysilane (TEOS) to introduce hydrophobic groups. Trimethylchlorosilane (TMCS) was used as a hydrophobic modification reagent to prepare hydrophobic catalysts, which exhibited a water droplet contact angle of 111.2°. At a temperature of 80 °C, the hydrophobic catalyst achieved a high MMA selectivity of over 95%. The samples were characterized using XRD, N2 adsorption, ICP, SEM, TEM, UV-vis, FT-IR, XPS, and water droplet contact angle measurements. Kinetic analysis revealed an activation energy of 22.44 kJ/mol for the hydrophobic catalyst.

Multifunctional carbon nanotubes coated stainless steel mesh for electrowetting, hydrophobic, and dye absorption behavior

Electrowetting behaviour for carbon nanotubes (CNT) grown on stainless steel mesh was investigated. The effect of temperature, time, and applied bias voltage on the contact angle of water droplets was studied. The impact of temperature variation on contact angle was also performed for the temperature ranging from 25 to 70 °C. A decrement of contact angle by 68% was observed for the mentioned range indicating a transition from a hydrophobic to hydrophilic nature. A similar trend was observed on the application of electric potential to the CNT-modified stainless-steel mesh ranging from 0 to 8 V with a transition of contact angle from 146 to 30 deg respectively. A comparative analysis for the contact angle variation with time for CNT-coated mesh and uncoated mesh was performed for 180 min. It is observed that uncoated mesh shows a reduction in contact angle to 0 deg with time while the CNT coated mesh shows surplus hydrophobicity with a 2 deg decrement in the extent of time. CNT-modified mesh successfully absorbs 95% of rhodamine B (RB) dye and detergent from water in 10 cycles.

Cellulose Nanofiber as Mask/Personal Protective Equipment Surface Agent for Enhanced Anti-Bacterial Performance

The utilization of face-covering masks as an extended form of personal protective equipment has led to exponential waste measures during the COVID-19 pandemic, with estimations of up to 7200 tons of medical-type waste daily. A primary cause of this waste is surgical layered disposable masks that are constructed by melt-blown nonwovens usually made of non-biodegradable thermoplastic polymers like polypropylene. To increase widespread sustainable options to the public, commercialized or do-it-yourself-based fabric masks serve as a solution, but their resistance to harmful molecules is less than that of the medical-grade masks due to the fabric structure that leaves space for penetration. This project examines a water-soluble dispersion composed of cellulose nanofiber and polyvinyl alcohol, as a spray agent capable of treating the mask fabric surface to promote protection and sustainability against harmful aerosol particles. Cellulose nanofiber spray is also low-cost and biocompatible and could allow multi-use through home laundering. Polyvinyl alcohol was chosen as the water-soluble bonding system and polymer matrix to effectively adhere cellulose nanofiber onto the mask surface. This project follows the biomimic concept of dragonfly wings having uneven nanopillar surfaces to trap and rip bacterial membranes, as the spray decreases the water droplet contact angle on fabric surface, resulting in an increase in adhesion for incident bacteria and/or viruses.

Preparation of super-hydrophobic BN nanotube mesh and theoretical research of wetting state

In this study, we have fabricated stainless steel mesh with columnar super-hydrophobic boron nitride nanotubes (BNNTs) through the ‘gas-liquid-solid’ mechanism annealing method. We employed iron (Fe) powder as the catalyst and utilized boron (B) and boron oxide (B2O3) as the raw materials. The synthesis took place within a tubular furnace, operating under an NH3 atmosphere at a temperature of 1250C∘. The contact angle of water droplets on the experimental surface measures approximately 150∘, while the sliding angle is approximately 3∘. In the next place, the laboratory carried out a series of experiments on the tensile properties, corrosion resistance, and erosion resistance of the prepared samples. The experimental results showed that the sample material had good mechanical properties and corrosion resistance. In addition, the erosion resistance test results showed that the sample material even at high speed (2800 rpm/min). After washing the sample for 5 min, the surface of the material still has good wettability (contact angle is 136.49∘). Finally, droplet bouncing experiments have demonstrated that the adhesion force on the surface of the boron nitride nanotube stainless steel mesh is notably minimal, indicating its substantial hydrophobic properties. Additionally, we conducted an investigation into the wetting interaction between droplets and the surface of the boron nitride nanotube stainless steel mesh. By applying the Wenzel and Cassie formulas and considering the pertinent geometric parameters of the material surface, we theoretically elucidated that, upon contact, the droplets assume a ‘Cassie’ state on the surface of the super-hydrophobic boron nitride nanotube stainless steel mesh. The research results show that the superhydrophobic boron nitride nanotube stainless steel mesh has broad application prospects in the fields of hydrogen storage, sewage treatment and oil-water separation.

Cotton fabrics modified with tannic acid/1-eicosanamine grafting layer for oil/water separation

The wettability of the surface of hydrophilic cotton fabrics was modified using a one-step protocol with tannic acid (TA) to provide its excess catechol groups to be grafted with 1-eicosanamine at pH 8.5 and room temperature with catalysts CuSO4/H2O2. The modification over the synthesis conditions revised the contact angles of water and diiodomethane droplets from 132.68 ± 0.49° to 143.95 ± 0.80° and from 100.08°±1.42° to 82.96 ± 1.38°, respectively. The corresponding dispersive of the so-yielded cotton surface ranged from 8.6 to 16.0 mJ/m2, and the polar components ranged from 0.08 to 2.7 mJ/m2, much lower than polytetrafluoroethylene. The modified cotton fabrics are omniphobic and can repel water and commercial oil products. The absorption tests revealed that the modified cotton fabrics absorbed 1.10 g hexane/g cotton by contacting hexane (top)-water (bottom) layers and absorbed 1.26 g hexane/g cotton by contacting water first for 30 s, then hexane for another 30 s. The modified fabrics reveal good absorption reusability as hexane absorbent is even pre-saturated with water. This conclusion is also valid for commercial unleaded gasoline #95 and diesel. A parametric study revealed that the added catalysts and prolonged reaction time would enhance the hydrophobicity of the surface. These modified cotton fabrics can absorb oil from water and oil spills. Mechanisms corresponding to this observation are discussed.

Extraction and characterization of cellulose microfibers from cornhusk for application as reinforcing agent in biocomposite

This study aims to extract and characterize cellulose microfibers from cornhusk, an agricultural by-product. The extracted fibers will then be used as a reinforcing agent in a biocomposite made of thermoplastic corn starch. The process of extracting cellulose microfibers involved two treatments: sequential alkali treatment (using sodium hydroxide at 120 °C for 120 min) and peroxide bleach treatment (using hydrogen peroxide at 90 °C for 60 min). Various techniques such as Fourier transform infrared (FTIR), X-Ray diffraction (XRD), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA) were employed to characterize the extracted fibers. The properties of the composite were examined through tensile strength tests, contact angle measurements, and UV–Vis spectrophotometry. The study found that cellulose microfibers were successfully extracted from cornhusks, with a diameter of 7 to 30 μm and a crystallinity of 65 %. The treated fibers showed gradual degradation between 150 °C and 350 °C, indicating a lower amount of non-cellulosic substances compared to untreated cornhusks. Adding 10 % of the microfibers to the thermoplastic starch composite increased the tensile stress at breaking and the Young's modulus, but decreased the contact angle of water droplets and the film's transparency.

Effects of ultrasound combined with hydrothermal treatment on the quality of brown rice

In order to improve the rough mouthfeel of brown rice, the effects of ultrasound (U) combined with hydrothermal (H) treatment on texture, sensory score and cooking quality of brown rice were studied, and the improvement mechanism was revealed from the aspects of room temperature water absorption, water droplet contact angle, microstructure and starch ordered structures. The results showed that ultrasound hydrothermal treatment cycle (UH-UH) can significantly improve the eating quality of brown rice. After UH-UH, the hardness, chewiness, optimal cooking time and volume expansion rate all reached to the level of white rice, and the stickiness significantly increased from 0.126 N of the control to 1.114 N. The sensory score of cooked brown rice rose from 57.37 to 76.70. On the other hand, room temperature water absorption rate far exceeded that of white rice, and the water droplet contact angle and relative crystallinity decreased significantly. In addition, scanning electron microscopy found that the cracks and micropores on the surface of treated brown rice grains increased greatly, which may be the underlying reasons for the improvement in the eating quality of brown rice. This study helps to provide a new way for producing high-quality brown rice.

The design and performance research of PTFE/PVDF/PDMS superhydrophobic radiative cooling composite coating with high infrared emissivity

High infrared emissivity in the atmospheric transparent spectral band, high reflectivity in the solar radiation band, self-cleaning and no heat treatment process are crucial for the application of the radiative cooling materials. In this work, a superhydrophobic radiative cooling composite coating was facilely prepared by using two sizes of polytetrafluoroethylene (PTFE) particles as main fillers and silica (SiO2) nanoparticles as auxiliary fillers, and polydimethylsiloxane (PDMS) and polyvinylidene fluoride (PVDF) as binders. The coating can be scraped onto the substrate through a scraper without any heat treatment procedure. The water droplet contact angle (WCA) and rolling angle (SA) of the coating can reach a maximum of 158 ± 0.5° and a minimum of 3 ± 0.3°, respectively. The average reflectance of the coating in the visible spectral band was around 90.6%. The average infrared emissivity of the coating in 8 ∼ 13 µm spectral band was about 0.989. The test results show that the coating has excellent self-cleaning and cooling properties. Furthermore, the coating also exhibits good abrasion resistance, preferable adhesion performance, ultraviolet radiation resistance, high temperature stability, self-cleaning and anti-icing performance.

Performance Evaluation of a Multifunctional Road Marking Coating for Tunnels Based on Nano SiO2 and TiO2 Modifications

Multifunctional road marking coatings with the functions of high-temperature stability, degradation of exhaust gas, and self-cleaning are of great significance for the safe operation and environmental protection of tunnels. This article uses active acrylic resin and an organosilicon hydrophobic agent as the base material, selects expanded vermiculite and glass microspheres as insulation fillers, and uses ammonium polyphosphate, pentaerythritol, melamine, and aluminum hydroxide as high-thermal-stability systems to prepare a two-component road marking coating base material. Then, nano SiO2 and modified nano TiO2 are added as modifiers to prepare a multifunctional road marking coating for tunnels. The physical and chemical properties of multifunctional road marking coatings are evaluating based on laboratory tests including thermogravimetry and derivative thermogravimetry, differential scanning calorimetry, infrared spectroscopy, scanning electron microscopy, exhaust degradation, and contact angle tests. The results indicate that the developed multifunctional road marking coating effectively reduces the thermal conductivity of the carbon layer through physical changes in the flame retardant system and the heat resistance formed by the high breaking bond energy of nano SiO2 during the combustion process. It forms a ceramic-like structure of titanium pyrophosphate with nano TiO2 that is beneficial for improving flame retardancy without generating harmful volatile gases and has good flame retardant properties. N–V co-doping reduces the bandgap of TiO2, broadens the absorption range of visible light by nano TiO2, improves the catalytic efficiency of visible light, and achieves the degradation efficiency of the four harmful components NOx, HC, CO, and CO2 in automotive exhaust by 23.4%, 8.3%, 2.5%, and 2.9%, respectively. The solid–liquid phase separation in the multifunctional road marking coating in the tunnel causes the formation and accumulation of nano SiO2 and TiO2 particles on the coating surface, resulting in a microstructure similar to the “micro–nano micro-convex” on the lotus leaf surface and making a water droplet contact angle of 134.2° on the coating surface.

Impact of argon dielectric barrier discharge cold plasma on the physicochemical and cooking properties of lightly-milled rice

This study investigated the influence of argon dielectric barrier discharge-cold plasma (DBD-CP) applied at different voltage settings (1 kV and 2 kV) and exposure durations (5 min and 10 min) on the physicochemical properties, cooking behavior, textural attributes, and flavor characteristics of lightly-milled-rice (LMR). The DBD-CP treatment increased the brightness of untreated LMR from 62.93 to 76.69, and reduced the water droplet contact angle from 66.66° to 58.99° following a treatment of 2 kV-10 min. Moreover, the treatment enhanced the crystallinity and gelatinization enthalpy of LMR starch by 8.93% and 60.55%, respectively. Conversely, it led to a decrease in the amylose content by 7.66% when compared to the control group. Metabolomic analysis revealed a decrease in the content of key compounds involved in metabolic pathways, including amino acids, α-hydroxy acids, and GABA. The cooking experiment demonstrated a substantial reduction by 5.4 min in optimal cooking time, along with water absorption capacity and volume expansion rate increased by 54.19% and 68.42% in 2 kV-10 min DBD-treated LMR, respectively. Notably, DBD-CP treatment positively influenced the production of important aroma compounds such as alcohols, aldehydes, and ketones. Overall, DBD-CP proved to be an effective physical processing method for significantly enhancing the edible quality and aroma of LMR.

Chemically bound hydrophobic modification in hydrogel surface layer using poly(N-vinylamide)s

The novel hydrophobic surface modification of hydrogel structure, referred to as organohydrogel, was firstly achieved through the utilization of poly(N-vinylamide)s hydrogels, taking advantage of the property of polycation precursor. Following the shrinkage of poly(N-acetamide-co-N-vinylformamide), only the surface moiety was subjected to hydrolysis. Subsequently, a radical initiator was chemically tethered to the amino groups on the hydrogel surface to facilitate atom transfer radical polymerization (ATRP) of hydrophobic monomer, phenylethylacrylate. Hydrophobic layer characteristics were differentiated by varying hydrolysis time (xt) and ATRP time (yt), resulting in the creation of hydrophobic surface-modified gel (HSMgel). All HSMgels resulted in stable swelling ratio (S.R.) regardless of yt. The contact angle of water droplets increased gradually with both increasing xt and yt, from 17.6° to 91.9°, while maintaining a relatively constant S.R. The drying process of hydrophobic surface-modified HSMgels was accelerated, while that of precursor hydrophilic gels was delayed. These unique properties stemmed from the chemical structure of poly(N-vinylamide)s, which led to the formation of a chemically bound hydrophobic layer within the hydrogels.

Changes in the hydrophilicity of the surface of PADC under ionizing radiations: Anomalous increase of the contact angle of water droplets under protons

The contact angle of water droplets decreases above certain absorbed doses in the case of heavy ions (He, C and Kr ions). Similarly, monotonic decreases are seen due to exposures to corona discharge and UV lights. The present trends indicate that the hydrophilicity of PADC surface increases by the contribution of hydroxyl groups.In comparison, the contact angle increases due to proton irradiations up to 1.3×105 Gy. Then it begins to decrease monotonically with increasing the absorbed dose. The present anomalous trend is discussed based on the combination of the track overlapping model and the Young’s formula.