Keeping a Clean Surface under Water: Nanoscale Nipple Array Decreases Surface Adsorption and Adhesion Forces

While nanoscale nipple arrays are expected to reduce light reflection and/or dust contamination in some insects, similar structures have been reported in various marine invertebrates. To evaluate the anti-contamination property of the structure in aquatic regimes, we measured the adsorption and adhesion forces on the flat surface and MOSMITE™ (Mitsubishi Chemical Corporation, Tokyo, Japan), a synthetic material mimicking the nipple array, under water. A small force toward the surface occurred when the probe approached the substrate surface. This adsorption force was significantly smaller on MOSMITE™ than on the flat surface. The adhesion force toward the surface occurred when the probe was detached from the surface, and it was also significantly smaller on MOSMITE™ than on the flat surface. The adhesion force in the air was much greater than the force under water, and the force was also significantly smaller on MOSMITE™ than on the flat surface. In the aquatic regime, the nipple array provides less adsorption/adhesion properties for the surface and thus, the organisms would have less contamination of microparticles on their body surface. As the adsorption and adhesion forces are also involved in the attachment of cells, tissue, and larvae, less adhesive body surfaces should be beneficial for survival in aquatic environments, as well as land environments.

Effects of Humidity on Dust Particle Removal during Solar Panel Cleaning

Solar panel cleaning is important to maintain the efficiency of energy production. In this research, we investigated the effects of relative humidity and condensation on the effectiveness of cleaning. The dust particles are subjected to various forces once they are deposited on the surface of a solar panel. When the dust particles continue to build up, they are also subjected to the adhesion forces from the neighboring dust particles. The adhesion forces from the substrates and the neighboring particles are dependent on the ambient conditions. Fundamentally, the interaction between the adhesion force of particle-particle and particle-substrate under various conditions was discussed in this manuscript.

The choice of adhesive for the production of yarn glue method

It is proposed to use sericin, a component of silkworm cocoons, as an adhesive compound for the production of yarn by the adhesive method. An experiment was conducted to study the dependence of the adhesion forces of the binder to cellulose on the concentration of the adhesive substance on the example of solutions of PVA, PVA and sericin. A comparative analysis of this dependence is carried out. Mathematical models are constructed to predict the strength of the adhesive joint depending on the concentration of the adhesive composition. The calculation of the adhesion forces per one elementary fiber is carried out.

Accurate Electroadhesion Force Measurements of Electrostrictive Polymers: The Case of High Performance Plasticized Terpolymers

Electroadhesion is a phenomenon ruled by many characteristic intrinsic parameters. To achieve a good adhesion, efficient and durable, a particular attention must be provided to the adhesion forces between the involved parts. In addition to the size and geometry of electrodes, parameters of materials such as dielectric constant, breakdown electric field, and Young’s modulus are key factors in the evaluation of electroadhesion efficiency for electrostrictive polymers and electroactive devices. By analyzing these material parameters, a method is proposed to justify the choice of polymer matrices that are fit to specific electroadhesion applications. Another purpose of this work aims to demonstrate a possibility of accurately measuring the electroadhesion force. This physical parameter has been usually estimated through equations instead, because of the complexity in setup implementation to achieve highly precise measure. Comparisons based on the parameters criterion reveal that besides the intrinsic properties of material, some other parameters relating to its physical phenomena (e.g., saturation of dipolar orientation under high electric field leads to decrease dielectric constant), or physical behavior of the system (i.e., surface roughness reduces the active electrode area) must be thoroughly considered. Experimental results pointed out that plasticized terpolymer leads boosted electroadhesion performance compared to the other counterparts, up to 100 times higher than conventional polymers. The developed materials show high potential in applications of active displacement control for electrostrictive actuation.

Evaluation of the effects of nicotine on the friction of the articular cartilage and the reversion of the estrogen in vitro

Background: Osteoarthritis is a severe disease for menopausal women, especially for those who exposed in the smoking and second hand-smoking. This study investigated the effect of the nicotine and estrogen on the articular cartilage. Methods: The articular cartilages were treated by nicotine and estrogen in vitro. Then the frictional properties and morphology on the surface were investigated using atomic force microscope. Proteoglycan 4(PRG4), as the key boundary lubricant of articular cartilage was characterized. Results: Nicotine down-regulates the friction coefficient and secretion of PRG4 significantly and then the estrogen increase them again. The adhesion forces also showed the same trend due to the content of anti-adhesive PRG4. Discussion: This study demonstrated that the present concentration nicotine has a negative effect on the articular cartilage and the estrogen has a better protecting effect. This may provide a potential guide for OA prevention and treatment.

Theoretical and Experimental Analysis of Surface Roughness and Adhesion Forces of MEMS Surfaces Using a Novel Method for Making a Compound Sputtering Target

Achieving a compound thin film with uniform thickness and high purity has always been a challenge in the applications concerning micro electro mechanical systems (MEMS). Controlling the adhesion force in micro/nanoscale is also critical. In the present study, a novel method for making a sputtering compound target is proposed for coating Ag–Au thin films with thicknesses of 120 and 500 nm on silicon substrates. The surface topography and adhesion forces of the samples were obtained using atomic force microscope (AFM). Rabinovich and Rumpf models were utilized to measure the adhesion force and compare the results with the obtained experimental values. It was found that the layer with a thickness of 500 nm has a lower adhesion force than the one with 120 nm thickness. The results further indicated that due to surface asperity radius, the adhesion achieved from the Rabinovich model was closer to the experimental values. This novel method for making a compound sputtering target has led to a lower adhesion force which can be useful for coating microgripper surfaces.

Fabrication of an Electrically Conductive Adhesive for Skin Mounted Bioelectronic Devices

Background: Skin mounted bioelectronics are difficult to integrate with the skin since biocompatible adhesives are not conductive or unsuitable for long-term use. Skin conformability is essential but strong adhesives can damage soft tissue in younger and frail individuals as well as the device during removal. Developing a noninvasive long-lasting biocompatible conductive adhesive for skin that can be used with bioelectronics allows for better treatment options and the improvement of patient outcomes. Methods: This study creates a soft hydrogel using graphene oxide flakes (GO) and polyvinyl alcohol. Networked GO is reduced in a solution of sodium dithionite and sodium hydroxide to form a conductive network within the hydrogel. Adhesive properties are achieved by incorporating a polyacrylic acid polymer into the hydrogel with the addition of N-hydroxysulfosuccinimide (NHS) groups to the polymer. NHS reacts with amine groups found on tissue to form covalent bonds that can be released with a biocompatible trigger solution of sodium bicarbonate and glutathione. Results: Hydration of the hydrogel at 65°C demonstrated that the hydrogel swelled anistropically with swelling ratios of 1.05/1.06/5.5 (length/width/thickness). This showed that the hydrogel can integrate into various surfaces without deformation. The hydrogel demonstrated an impedance of 106.1~164.6 Ω⋅m (20~500 Hz), which is comparable to conventional devices. The hydrogel was chemically bound to amine functionalized polydimethylsiloxane (PDMS) and glass. Peel test showed peak adhesion forces of 100.5 N⋅m-1(Force⋅Width-1) when bound to PDMS or glass. Signal quality of the hydrogel showed that the hydrogels demonstrated ECG and EMG signals comparable to commercially available materials. Conclusions: The importance of this study is to create a soft material that bonds between electrodes and skin. The results demonstrate that the hydrogel has electrical characteristics comparable to conventional electrodes for use in ECG and EMG. In addition, it can create adhesion via chemical bonds that can be released on demand.

Modelling of the Motion and Interaction of a Droplet of an Inkjet Printing Process with Physically Treated Polymers Substrates

This study examines the effect of energetic surface treatment on the adhesion strength of high-density polyethylene (HDPE), polypropylene (PP) and polyethylene terephthalate (PET) substrates. The purpose of this work is to determine the surface wettability of polymers suitable for food contact. These plastics have been treated with various pre-treatment methods to improve surface tension and good adhesion for inkjet printing and avoid any visual changes. It is important to determine the adhesion of the ink to the polymer surface to improve post-consumer recycling. Digital inks have been tested on various treated plastics to analyse coating properties and adhesion forces in accordance with DIN ISO 2409 standards. The impact of the inkjet droplet on the treated and non-treated surface was also investigated using the COMSOL computer simulation software.

Local force titration of wood surfaces by chemical force microscopy

Chemical force microcopy, a variation of atomic force microscopy, opened the door to visualize chemical nano-properties of various materials in their natural state. The key function of this method is given by translating adhesion forces between a functionalized tip and the sample to chemical surface behavior. In force titration, these adhesion forces are studied in different pH buffers, which allows estimating the pKa value of the analyzed surface. Herein, we report the use of this method to study natural and chemically treated wood surfaces, which are of interest in sustainable material design. First, we show varying adhesion phenomena of OH- and COOH-functionalized tips on native spruce wood cells. Then, we demonstrate how peak force tapping with chemically functionalized tips can be used to estimate the pKa value of gold substrates (pKa ≈ 5.2) and different wood cell wall layers with high spatial resolution. Additionally, the swelling behavior of wood samples is analyzed in varying pH buffers. With the applied method, chemical surface properties of complex natural substrates can be analyzed. Graphical abstract

The Development of Fine Surface Roughness of FeCrAl Substrate by Gamma Alumina Coating Material Through Nickel Oxide Catalyst

The most commonly used method for protecting atmospherically exposed steel against corrosion, is the application of protective organic coating systems. It is widely recognized that the stability of the coating-substrate interface is related to the interfacial adhesion forces and electrochemical properties of this region. This study aim to develop fine surface roughness by ultrasonic and electroplating coating methods that applied for FeCrAl catalytic converter. This method consists of thwo methods which are ultrasonic bath that carried out by frequency of 35 kHz and various ultrasonic times of 1, 1.5, 2, 2.5 and 3 hours is imposed and the electroplating was conducted for several variation times of 15, 30, 45, 60 and 75 minutes, current density of 8 A/dm2. The result shows that the surface roughness of UB samples in between 0.11 to 0.21 µm, UBdEL samples of 0.81 to 2.17 µm, UB+EL samples of 0.64 to 1.63 µm and EL samples of 0.69 to 1.11 µm. The finest surface of each techniques are located at UB 1.5 h, UBdEL 45 minutes, UB 1.5 h+EL 30 minutes and UB 30 minutes. That data is supported by coating thickness of coated FeCrAl substrate where UB samples in between 2 -2.8 µm, UBdEL samples of 4.1 to 5 µm, UB+EL samples of 9.1 to 12 µm and EL samples of 6.2 to 11.3 µm.