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Electrostatic deposition of nanothin films on metal substrate
Thin solid film has been deposited by electrohydrodynamic spraying (electrospraying) onto a metal substrate. Electrospraying is a low-energy physical process in which tangential stress exerted by electric field on the surface of a liquid flowing form a capillary nozzle causes jet elongat...
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A novel microscale emitter employing a pointed carbon fiber (CF) can be used for electrospraying in mass spectrometric (MS) analysis. The carbon fiber is located coaxial with a fused silica capillary tube of 360 µm OD and 75 µm ID with its sharp tip extending 30 µm beyond the tube terminus. The electrospray ionization (ESI) process is simulated usi...
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... The traditional coating technology for the investigated components, i.e. wire die springs, is based on the electrostatic deposition process [39,40], with the described consequences of an inability to achieve a continuous and homogeneous, low-thickness film on the components, due to the difficulty of coating inside the coils of the springs, due to the Faraday cage effect [21]. Indeed, such electrostatic action makes it difficult to deposit the coating powder in the recesses between coils, or in the presence of areas with deep indentations, resulting in little or no coloration. ...
The subject of the present paper deals with the description of an innovative coating process, based on polymer powder fluidized bed technology, applied in combination with an adhesive silicone primer. This study aims to overcome the problems of traditional coating systems for mechanical complex-geometry components, for applications where high precision in thin film deposition and high coating uniformity, at a micrometer level, are required. In this context, the case study of wire die spring coating is here proposed, carrying out a validation of the proposed technical solution, compared to the traditional process based on electrostatic coating, through an aesthetic, morphological and mechanical experimental characterization. The results showed that the innovative deposition system ensures excellent aesthetic performance, depositing a homogeneous coating, with a constant thickness of ~15-20 μm, on the surface of the complex geometry component analyzed, as opposed to ~25-90 μm for the traditional process. The proposed technique also ensures an excellent coating uniformity both inside the coils and on the external surfaces, as well as a complete protective coverage of the springs and their uniform coloring, with significantly lower consumption of coating powder, thus verifying the full technological feasibility of the fluidized bed deposition process, which is applicable also on non-conductive surfaces. Finally, the surface morphology of the specimens coated with the advanced system showed a memory effect of the substrate, while the analysis of the mechanical behavior remarked a higher fragility in terms of scratch test resistance, typical of thin films, compared to the reference.
... Among other droplet reducing mechanism, research shows that the electrospray process is a capable, energy efficient process which produces a fine spray, [3,[12][13][14][15][16]. The meniscus is exposed to a heavy electric field so that the liquid desiccant is converted into a cone-jet by the electrostatic force, [17]. ...
... The configuration of emitters in a multi-electrospray set up can be as presented in Fig. 1 where there is a representation of a mono-hole system whose tip can be levelled or pointed, a double and a triple-hole emitter, [12]. Emitter configuration in multi-electrospray [12] Several researches have been done to analyse the interaction problem in multiplexed jets during electrospray, [13,21]. It has been found that the factors that affect jet behavior include the operating voltage, flow rate and emitter spacing in an array of emitter [12]. ...
... It has been found that the factors that affect jet behavior include the operating voltage, flow rate and emitter spacing in an array of emitter [12]. If one emitter is in operation and the distance between the emitters is reduced, more potential is needed to produce cone jet which is stable because of shielding effect [13]. The required potential decreases at a very close spacing. ...
When liquid desiccant systems are employed to dehumidify air electrospraying technique helps to increase the surface area of the liquid. Multiplexing of the jets by introducing several emitters for increased efficiency is commendable but, there is a tendency of the jets to cross talk with each other due to electrical shielding. Cross talking of jets will result in the failure of the jets to break properly into droplets for effective dehumidification. This piece of work analyzed the conditions for electrical shielding among jets which results in efficient electrospray. To evaluate how cross talking affects multiple emitter nozzles, the mathematical model was built by superimposing the electric potentials of one emitter in an array of emitters. A Computational Fluid Dynamics simulation model was developed to investigate the conditions for electrical shielding among jets during electrospray process with glycerol as the working substance. In flow modelling, Ansys Fluent with Volume of Fluid and the Taylor Dielectric model were involved. The flow rate that guarantees stability in the electrospray was determined together with the optimum voltage resulting in a spray current which reduces electrical shielding. An analysis on the electrical conductivity of the liquid to ensure stability and efficiency in electrospray was done. The pressure contours of the nozzle were determined together with velocity of the desiccant against density. Emitter spacing, applied voltage, flow rate and the electrical conductivity plays a pivotal role on the prevention of cross talking of jets during the electrospraying process.
... In addition, ESD is less expensive than chemical vapour deposition and vapour condensation, in which a large amount of precursor material is lost in the thin film production process, or than plasma spraying requiring high vacuum conditions. Finally, the film thickness and quality obtained with ESD technique can be controlled by adjusting different experimental variables (i.e., liquid flowrate and concentration of the precursor solution, applied voltage, deposition temperature, among others) [25][26][27][28], providing high versatility for multiple applications. Therefore, it is not surprising that this atomization technique has attracted considerable attention to the scientific community, with a large amount of applications in different fields such as the nuclear instrumentation, solar cells, fuel cells, lithium batteries, micro and nanoelectronic devices, biotechnology or some industrial applications, among many others [26][27][28][29][30][31]. ...
... Finally, the film thickness and quality obtained with ESD technique can be controlled by adjusting different experimental variables (i.e., liquid flowrate and concentration of the precursor solution, applied voltage, deposition temperature, among others) [25][26][27][28], providing high versatility for multiple applications. Therefore, it is not surprising that this atomization technique has attracted considerable attention to the scientific community, with a large amount of applications in different fields such as the nuclear instrumentation, solar cells, fuel cells, lithium batteries, micro and nanoelectronic devices, biotechnology or some industrial applications, among many others [26][27][28][29][30][31]. ...
... For this reason, dispersions of graphene oxide prepared in different ethanol-water mixtures having increasing ethanol content were evaluated. In these studies, the GO dispersion flowrate and glass substrate temperature in the ESD system were set at 13 μL min − 1 whereas the applied voltage and the H distance were adjusted in each experiment in order to obtain the cone-jet mode in the electrospray for maximum spray stability [25][26][27][28]32,33,40]. The speed and travel distance of the computer-controlled linear stage of the ESD system were kept at 0.5 mm s − 1 and 20 mm, respectively. ...
In this work, a solid phase microextraction procedure, denoted as Thin Film Microextraction (TFME), was combined with Laser-induced Breakdown Spectroscopy for the detection of several analytes in aqueous solutions (Cu, Cr, Ni and Pb). The adsorbent films, consisting of a thin layer of graphene oxide deposited on glass substrates, were generated by using the electrospray deposition technique (ESD). Several parameters affecting the quality and shape of the films resulting from the ESD process were studied, and the morphology and adsorption capacity of the films were evaluated. The generated films were used for extraction of the target analytes from aqueous solutions and, after extraction, the analytes-enriched adsorbents were analysed by LIBS without the need of any desorption or elution step. In order to assess the analytical capability of the TFME-LIBS procedure, different analytical figures of merit of the proposed TFME-LIBS methodology were evaluated. The obtained limits of detection were 14 μg kg⁻¹ for Pb and 15 μg kg⁻¹ for the rest of the tested analytes. Measurement repeatability was better than 4% RSD at low concentration level (20 μg kg⁻¹) but deteriorated by increasing the concentration level at 100 μg kg⁻¹, with %RSD ranging from 3.6% (Cr) to 24% (Pb). Method trueness, evaluated from the analysis of a real sample of bottled water, led to recovery values in the range 85%–106%.
... There are several benefits of using the electrospray technique such as efficient process, easy operation, good materials compatibility, and a uniformly and homogenously deposited layer [82,84]. However, during the customary electrospray where a considerable space between the substrate and the nozzle takes a place, the charged particles become unbalanced and the deposition area increases. ...
This study aims to the preparation and characterization of the C60 thin film. The C60 thin film was prepared and deposited using two steps preparation/deposition processes, namely laser ablation and electrospray methods, respectively. The deposition process was achieved under an electric field. this application was studied as an electrochemical biosensor for the prostate-specific antigen (PSA).
... The electrostatic spray deposition (ESD) technique is a simple process for thin-film preparation. Normally, nanostructure thin films such as metal, metal oxide, and polymer [12][13][14][15] can be prepared by this method. In this technique, the precursor solution is fed through a metal nozzle. ...
... The properties of the deposited film are dependent on the deposition parameters such as substrate temperature and deposition times. In addition, the ESD technique uses a scalability system to prepare large-area films with more advantages such as low-temperature deposition, operation at ambient atmosphere, and repeatability [14]. In other reports, the ESD technique was used to prepare GO or reduced GO thin films for various applications such as super hydrophilic surfaces and energy storage. ...
In this work, transparent and flexible humidity sensors based on graphene oxide film were prepared using the electrostatic spray deposition technique. Graphene oxide (GO) powder was synthesized using the modified Hummer’s method, which was used as a precursor for thin-film deposition. The properties of GO films were characterized by X-ray diffraction, field-emission scanning electron microscope, Raman spectroscopy, Fourier transform infrared spectroscopy, and UV–Vis spectrophotometer. The effect of substrate temperature on the sensor properties was observed. The impedance of the device exhibited a lower value when increasing the relative humidity level. In addition, the device showed high sensitivity of more than 1117.3, fast response with 5 s, more than 60% optical transparency, and flexible property more than 2000 cycles. In addition, the equivalent circuit models of the devices were evaluated from complex impedance measurements used to explain the sensing mechanisms of the device.
... High resolution Scanner was used for scanning photo papers with 1200 dpi scan resolution. Computer based image analysis software Image-J-2016, Version 1.37.1 was used to analyze the scanned images and spectrum (Jaworek et al., 2009;Mishra et al., 2014). ...
An electrostatic induction spray charging system as attachment to powered knapsack mist-blower was developed and evaluated for the performance. A high voltage generator was fabricated on the basis of Cockcroft-Walton voltage multiplier principle with input of 6 V DC battery to provide high voltage required at the developed charging electrode assembly (Model-I and II) for inducing electrostatic charge on spray droplets. The working
prototypes were evaluated for charge to mass ratio (mC.kg-1) at five electrode potentials (1kV, 2 kV, 3 kV, 4 kV and 5 kV), four electrode placement positions (0 mm,5 mm, 10 mm and 15 mm) and five distances (50 cm, 100cm, 150 cm, 200 cm and 250 cm) from the nozzle. Model-II with electrode voltage potential at 5 kV and EPP at 5 mm shown the maximum CMR value (1.088 mC.kg-1),.In contrast with commercial system (ESS-MBP90)
it was observed that except at 50 cm distance from nozzle, Model-II (at 4 kV and 5 kV)
surpassed commercial system in CMR from 100 cm to 250 cm distance. To avoid air blast injury of plant, the nozzle has to be 100 cm to 150 cm away from the plant. The droplet spectrum of the developed system was analyzed and observed that the size of droplets were 100 to 200 μm. The deposition efficiency of the developed system was on par with that commercial unit, and was within the range of 60 to 70 per cent. The developed system found to be cost effective and significantly consistent than the commercial system.
... Previous works have established that only a thin volume of the MnO x electrode participates in the charge-storage mechanism under EC demands [1], which makes synthesizing MnO x thin-films an attractive solution for pseudocapacitive needs. Electrostatic Spray Deposition (ESD) is a thin-film synthesis technique, which essentially involves the disintegration of a precursor solution into an aerosol spray upon the application of a high voltage between the feeding source and a grounded preheated substrate [13][14][15][16]. ESD provides the feasibility to tailor the film morphology by fine-tuning the deposition parameters, without the need for vacuum or addition of binders making it a popular method for EES applications [15][16][17][18][19][20][21][22][23]. ...
In this study, three binder-free manganese oxide-carbon nanotube (MnOx-CNT) composite films were synthesized using electrostatic spray deposition (ESD) and evaluated as electrochemical capacitor (EC) electrodes in aqueous media. The MnOx-CNT 9-1 composition exhibited superior electrochemical performance as compared to both the pristine MnOx and MnOx-CNT 8-2 composite films, exhibiting a high specific capacitance of 281 F g-1 in addition to excellent rate handling and cyclability. In order to investigate the practical viability of the MnOx-CNT 9-1 electrodes, a comprehensive two-electrode analysis was performed using activated carbon (AC) counter electrodes for different mass ratios to obtain optimal energy-power trade-off. The asymmetric capacitor with the AC electrode with a mass 2.6 times that of the MnOx-CNT 9-1 electrode exhibited the best energy-power characteristics reaching a maximal gravimetric energy density of 30.3 Wh kg-1; the excellent electrochemical performance of the asymmetric capacitor is attributed to the wider cell voltage of 2V as well as the high gravimetric capacitance of the ESD- based MnOx-CNT composite cathode.
... The advantages of spray by EHD include simple operational steps, an efficient process, an evenly deposited layer, and a good compatibility of materials. 8,9 The electrospray techniques have been used for preparing numerous different thin films from biomaterials, 10 to composite metals, 11 ceramics, 3 and nonmetal oxides. 12−16 Conventional electrospray process uses a working distance of 10 cm (far field) so that the deposition area is too large to collect the micropatterns. ...
We present for the first time an investigation on the spraying modality for the pyroelectrohydrodynamic (pyro-EHD) system. We show that the pyro-EHD spray (p-Spray) works well in the range from far field (d > 10 mm) to near field (d < 2 mm) without the need of external voltage and without the needs to change the experimental apparatus in that wide range of distances. Because the proposed method works without a counter electrode, no limitations are connected with the geometric shape of the substrate on which the spray coating is deposited. We report on several examples of the formation of disperse sprayed droplets, whose size can be varied between hundreds of micrometers and hundreds of nanometers, as well as on the production of sprayed pattern footpaths. The results reported here demonstrate the direct writing of spray patterns of nano/microdroplets with different materials in a very wide range, that is, from low- to high-viscous liquid solutions. Finally, as an example of application, we show the use of the p-Spray for the fabrication of silver-coated devices showing antimicrobial properties of the pattern produced by the p-Spray through a customizable and environmental friendly approach.
... ESD is an electrohydrodynamic spraying technique, which essentially involves the disintegration of a precursor solution into an aerosol spray upon the application of a high voltage between the feeding source and a grounded preheated substrate. The ability to tailor the film morphology by fine-tuning deposition parameters, without the need for vacuum, is what makes ESD an attractive and cost-effective thin-film synthesis method [24][25][26][27][28][29]. The ESD-derived manganese oxide films were able to deliver specific capacitances as high as 225 F·g −1 from 72 F·g −1 upon electrochemical cycling in neutral aqueous media. ...
In this study, porous manganese oxide (MnO
x
) thin films were synthesized via electrostatic spray deposition (ESD) and evaluated as pseudocapacitive electrode materials in neutral aqueous media. Very interestingly, the gravimetric specific capacitance of the ESD-based electrodes underwent a marked enhancement upon electrochemical cycling, from 72 F∙g-1 to 225 F∙g-1, with a concomitant improvement in kinetics and conductivity. The change in capacitance and resistivity is attributed to a partial electrochemical phase transformation from the spinel-type hausmannite Mn₃O₄ to the conducting layered birnessite MnO₂. Furthermore, the films were able to retain 88.4% of the maximal capacitance after 1000 cycles. Upon verifying the viability of the manganese oxide films for pseudocapacitive applications, the thin films were integrated onto carbon micro-pillars created via carbon microelectromechanical systems (C-MEMS) for examining their application as potential microelectrode candidates. In a symmetric two-electrode cell setup, the MnO
x
/C-MEMS microelectrodes were able to deliver specific capacitances as high as 0.055 F∙cm-2 and stack capacitances as high as 7.4 F·cm-3, with maximal stack energy and power densities of 0.51 mWh·cm-3 and 28.3 mW·cm-3, respectively. The excellent areal capacitance of the MnO
x
-MEs is attributed to the pseudocapacitive MnO
x
as well as the three-dimensional architectural framework provided by the carbon micro-pillars.
... Considerable advantage of the EHD method is the easy upscaling of the printing to RECEIVED larger surfaces [3], while the production rate is still limited by the number of the emitting needles. At the same time, EHD printing is a good alternative to the most advanced manufacturing techniques such as lithography, because it is not necessary to create special process conditions [4] and follow the procedures in many interdependent steps [5]. ...
In implantable systems, most of the surfaces have to be treated to become biologically active. Herein, we use the electrohydrodynamic printing method (EHD) that is based on the same principle as the electrospinning technology for the modification of implantable surfaces with biocompatible polymers with microscale precision. Application of polymeric micropatterns on implantable surfaces improves their interaction with the host tissue, enables the delivery of growth factors, antibiotics, anti-inflammatory cytokines etc. from the implant surface and controls the immune responses to the implant via controlling the attachment of immune cells, such as macrophages. Surface patterns with a resolution of less than 50 μm can be created using an electrohydrodynamic printing, a template-free and single-step process. Thanks to the similarity of the EHD process to electrospinning, the 4SPIN® laboratory device for nanofibrous layers preparation was modified for patterning of primary conductive, but in some cases, also for non-conductive, substrates. Reduction of distance between the electrodes (emitter, collector) to only several millimetres causes that the gradient of electrostatic field preserves only the stable phase of the standard electrospinning process and enables us to deposit periodic and regular structures. Process parameters, as well as solution properties, play key role in the patterning process. In recent work, we used EHD for the deposition of parallel stripes of photocrosslinkable, cell adhesive polymeric composites with spacing of around 20 micrometres onto medical grade titanium substrates. We focused especially on optimisation of the process parameters - the solution, voltage, feed rate and collection speed. Using a very rapid movement of the grounded rotating collector we were able to prepare polymeric stripes as well as angled multilayer structures on titanium substrates. These patterns have highly precise periodic distances between individual stripes. A titanium foil patterned by mixture of modified polyethylene glycol and modified gelatin was used for in vitro tests.
