Electrohydrodynamic Technique Research Articles

All-printed and highly stable organic resistive switching device based on graphene quantum dots and polyvinylpyrrolidone composite

We propose all printed and highly stable organic resistive switching device (ORSD) based on graphene quantum dots (G-QDs) and polyvinylpyrrolidone (PVP) composite for non-volatile memory applications. It is fabricated by sandwiching G-QDs/PVP composite between top and bottom silver (Ag) electrodes on a flexible substrate polyethylene terephthalate (PET) at ambient conditions through a cost effective and eco-friendly electro-hydrodynamic (EHD) technique. Thickness of the active layer is measured around 97nm. The proposed ORSD is fabricated in a 3×3 crossbar array. It operates switching between high resistance state (HRS) and low resistance state (LRS) with OFF/ON ratio ∼14 for more than 500 endurance cycles, and retention time for more than 30days. The switching voltage for set/reset of the devices is ±1.8V and the bendability down to 8mm diameter for 1000 cycles are tested. The elemental composition and surface morphology are characterized by XPS, FE-SEM, and microscope.

Design of versatile printed organic resistor based on resistivity (ρ) control

We demonstrate the design and fabrication of a printed organic resistor based on resistivity (ρ) control method. Two types of resistor are reported by utilizing three types of material poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate), poly(methyl methacrylate), and silver (Ag) nano-particles. Materials are blended for the required value of resistivity (ρ), to overcome the size and resistance value constraints of the printed resistors. The design function ρ(x) is also proposed to estimate the required resistivity value, and this function is obtained from the measured resistivity and mixing ratio of materials. The proposed resistivity design function is verified by comparing measured and theoretical estimated values of the resistivity. The resistors are fabricated on polyethylene terephthalate substrate through electro-hydrodynamic technique. The proposed two types of organic resistors are electrically and mechanically characterized by using various methods of their current–voltage (I–V) relation analysis, endurance time, bendability, heating temperature analysis, and frequency response.

Surface-Enhanced Raman Scattering Using Silver Nanoparticles Produced by Laser Ablation in Liquid

The active substrates with rings of silver nanoparticles arising by drying of sessile colloid drops were used for realization of the surface-enhanced Raman scattering. The colloids have been produced by laser ablation in water using pulse Yb fiber laser. The droplets with diameter down to 10 μm were dispensed by electrohydrodynamic technique by means of pyroelectric field produced by lithium tantalate plate. The optimal spatial distribution of hotspots was obtained for substrate covered by the micron-size rings of silver nanoparticles. The method was applied for various organic molecules rhodamine 6G, thymine, and RNA with enhancement factor up to 105.

Organic non-volatile memory cell based on resistive elements through electro-hydrodynamic technique

By utilizing electro-hydrodynamic (EHD) technique, we propose an organic non-volatile memory cell capable of storing one bit data. It consists of an organic resistor and a memristor, which stores a bit in the memristor and be read by a voltage divider operation. The proposed device is fabricated by utilizing the materials poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) for resistor and zirconium dioxide (ZrO2) for memristor. The fabricated device is in the size of 4mm×2mm, and thickness of the memristor and the resistor are 76nm and 1μm, respectively. To verify the device, reliable read/write operations are presented for more than 100 cycles. The device is also measured a stable performance against bending, and a minimum applicable bending diameter is 12mm. The device is analyzed for surface morphology by taking SEM images.

Condensation enhancement by means of electrohydrodynamic techniques

Abstract Short state-of-the-art on the enhancement of condensation heat transfer techniques by means of condensate drainage is presented in this paper. The electrohydrodynamic (EHD) technique is suitable for dielectric media used in refrigeration, organic Rankine cycles and heat pump devices. The electric field is commonly generated in the case of horizontal tubes by means of a rod-type electrode or mesh electrodes. Authors proposed two geometries in the presented own experimental investigations. The first one was an electrode placed just beneath the tube bottom and the second one consisted of a horizontal finned tube with a double electrode placed beneath the tube. The experimental investigations of these two configurations for condensation of refrigerant R-123 have been accomplished. The obtained results confirmed that the application of the EHD technique for the investigated tube and electrode arrangement caused significant increase in heat transfer coefficient. The condensation enhancement depends both on the geometry of the electrode system and on the applied voltage.

Novel preparation of controlled porosity particle/fibre loaded scaffolds using a hybrid micro-fluidic and electrohydrodynamic technique

The purpose of this research was to produce multi-dimensional scaffolds containing biocompatible particles and fibres. To achieve this, two techniques were combined and used: T-Junction microfluidics and electrohydrodynamic (EHD) processing. The former was used to form layers of monodispersed bovine serum albumin (BSA) bubbles, which upon drying formed porous scaffolds. By altering the T-Junction processing parameters, bubbles with different diameters were produced and hence the scaffold porosity could be controlled. EHD processing was used to spray or spin poly(lactic-co-glycolic) (PLGA), polymethysilsesquioxane (PMSQ) and collagen particles/fibres onto the scaffolds during their production and after drying. As a result, multifunctional BSA scaffolds with controlled porosity containing PLGA, PMSQ and collagen particles/fibres were obtained. Product morphology was studied by optical and scanning electron microscopy. These products have potential applications in many advanced biomedical, pharmaceutical and cosmetic fields e.g. bone regeneration, drug delivery, cosmetic cream lathers, facial scrubbing creams etc.

Study on Photoelectric Properties of Dye-Sensitized Solar Cells Based on Thixotropy Electrolyte

A series of experiments have been carried out to study on the efficiencies in solar energy materials and solar cells. Dye-sensitized solar cells (DSSCs) are good examples of where the quality of the nanomaterials and their interfacial properties are important to device performance. In this report, Nanometer TiO2 sol for coating film was prepared by cooperating hydrothermal colloidal sol with organic polymer dispersing agent (PVA). Nanocrystalline TiO2 porous films were prepared by using electro-hydrodynamic technique (EHD). The results show the films prepared by EHD technique have multilevel hierarchical structure, therefore, better optical scattering properties. Different constituent quasi-solid electrolytes with blood mimetic thixotropy were prepared by cooperating ionic liquid electrolyte with nanometer TiO2 colloidal sol synthetized by sol-gel method. The resulting Quasi-Solid-State dye-sensitized solar cells consist of nanoporous TiO2 Film and the dye N3, show conversion efficiencies up to 3.7 percent (8. 51 percent with a mask).

Selective Catalytic Reduction of Nitric Oxide by Ammonia over V2O5/TiO2 in a Hollow Cylindrical Catalyst under Enhancing Effect of Electrohydrodynamics: A Kinetic Modeling Study

Emissions of nitrogen oxides (NOx) in fuel combustion from stationary and mobile sources contribute to the greenhouse effects and cause a variety of environmentally harmful results. Meanwhile, the selective catalytic reduction (SCR) of NOx using ammonia over a vanadia-based catalyst in heterogeneous reactors is still a well-proven technique for NOx abatement. However, to meet forthcoming restrictive legislation, greater De-NOx performance can be achieved by eliminating operational setbacks such as diffusion resistance, poor catalyst activity at low temperatures, etc. In this study, an electrohydrodynamic (EHD)-SCR model was developed to evaluate the enhancing effect of the EHD technique on NH3-SCR of NO through a hollow cylindrical catalyst. Computational investigations were performed based on the proposed model in different operational conditions to examine the effect of various operating parameters on SCR enhancement. Simulation results showed that catalyst utilization was intensified significantly by EHD application and generation of additional flow known as EHD-induced secondary flow through the catalyst porous layer, which undermined the proposed drawbacks of the catalyst medium and provided higher catalyst effectiveness with greater NO conversion. Results also indicated that the maximum enhancement of almost 4.2-fold could be obtained for NO conversion with electric potentials and operating temperatures of 150–270 V and 150–165 °C, respectively.

A portable device for in situ deposition of bioproducts

The electrohydrodynamic (EHD) technique has traditionally been confined to the bench-top. Recently, a portable EHD device was constructed that allows the process to be applied in a much more flexible and versatile manner. In this article, the effect of electrode and collector height on the fibers generated by EHD and wound-dressing forming capabilities of the device tested on different types of simulated wound morphologies were investigated. Dressings were also fabricated on living tissue to investigate jet behavior and product morphology. The EHD device was found to be capable of controlled deposition of micrometer-sized poly(D,L-lactide-co-glycolide) acid fibers that can form an opaque, waterproof wound dressing on human skin within a few minutes with excellent adherence.

Patterning of graphene microscale structures using electrohydrodynamic atomisation deposition of photoresist moulds

In this reported work, a graphene suspension was atomised and deposited using the electrohydrodynamic atomisation technique, enabling the formation of a wide range of graphene thin films. The influences of the atomisation-substrate distance on the characteristics of the graphene films and their sheet resistances were analysed. A distance of 3 mm was found to be the optimum deposition distance for this graphene suspension to produce an even film and a low sheet resistance. At a lower and a higher working distance the graphene films exhibited a sharp-angled heave surface behaviour and a high sheet resistance. In addition, electrohydrodynamic atomisation combined with a photolithography polymeric micromoulding technique was used to form graphene structures. After removing the photoresist micromould, the graphene structures remained under well-arranged characteristics. After two layers of electrohydrodynamic atomisation deposition at a working distance of 3 mm, the thickness of the film was approximate to 400 nm and exhibited a sheet resistance of 127.5 sq(-1) (ohms per square).

Electrohydrodynamic atomization approach to graphene/zinc oxide film fabrication for application in electronic devices

Graphene-based composites represent a new class of materials with potential for many applications. Metal, semiconductor, or any polymer properties can be tuned by attaching it to graphene. Here, a new route for fabrication of graphene based composites thin films has been explored. Graphene flakes (<4 layers) and a well-known semiconductor zinc oxide (ZnO) (<50 nm particle size) have been dispersed in N-methylpyrrolidone and ethanol, respectively. Thin film of graphene flakes is deposited and decorated with ZnO nanoparticles to fabricate graphene/ZnO composite thin film on silicon substrate by electro hydrodynamic atomization technique. Graphene/ZnO composite thin film has been characterized morphologically, structurally and chemically. To investigate electronic behavior of the composite thin film, it is deployed as cathode in a diode device i.e. indium tin oxide/poly (3,4-ethylenedioxythiophene) poly (styrenesulfonate)/polydioctylfluorene-benzothiadiazole/(graphene/ZnO). The J–V analysis of diode device has shown that at voltage of 1 V, the current density in organic structure is at low value of 4.69 × 10−3 A/cm2 and when voltage applied voltage is further increased; the device current density has increased by the order of 200 that is 1.034 A/cm2 at voltage of 12 V.

Electrosprayed core–shell polymer–lipid nanoparticles for active component delivery

A key challenge in the production of multicomponent nanoparticles for healthcare applications is obtaining reproducible monodisperse nanoparticles with the minimum number of preparation steps. This paper focus on the use of electrohydrodynamic (EHD) techniques to produce core–shell polymer–lipid structures with a narrow size distribution in a single step process. These nanoparticles are composed of a hydrophilic core for active component encapsulation and a lipid shell. It was found that core–shell nanoparticles with a tunable size range between 30 and 90 nm and a narrow size distribution could be reproducibly manufactured. The results indicate that the lipid component (stearic acid) stabilizes the nanoparticles against collapse and aggregation and improves entrapment of active components, in this case vanillin, ethylmaltol and maltol. The overall structure of the nanoparticles produced was examined by multiple methods, including transmission electron microscopy and differential scanning calorimetry, to confirm that they were of core–shell form.

Plasmon resonance of gold nanorods for all-optical drawing of liquid droplets

We present a laser-assisted system for dispensing liquid micro-droplets by near infrared illumination of a pyroelectric crystal functionalized with gold nanorods embedded into polyvinyl alcohol. The non-invasive near infrared source resonates with the plasmon oscillations of the gold nanorods, providing a controlled thermal stimulus able to generate the pyroelectric effect. The resulting electric field interacts electro-hydrodynamically with a liquid reservoir leading to precise drawing of micro-litre droplets. This laser-assisted electro-hydrodynamic technique may open the way to the development of more compact and non-invasive nano-dispensing devices.

Numerical investigation of using various electrode arrangements for amplifying the EHD enhanced heat transfer in a smooth channel

Abstract Forced convection heat transfer enhancement with electrohydrodynamic (EHD) technique of turbulent flow inside a smooth channel has been numerically investigated. A two dimensional numerical approach has been chosen to evaluate the local and average heat transfer coefficient. In addition, the swirling flow pattern in the presence of an electric field has been studied. To achieve higher enhancement while using multiple electrodes, variety of electrode arrangements have been examined for specified values of Reynolds number, applied voltage, and wire radius. The results demonstrate that different electrode arrangements cause significant improvement of the heat transfer coefficient.

Targeted electrohydrodynamic printing for micro-reservoir drug delivery systems

Microfluidic drug delivery systems consisting of a drug reservoir and microfluidic channels have shown the possibility of simple and robust modulation of drug release rate. However, the difficulty of loading a small quantity of drug into drug reservoirs at a micro-scale limited further development of such systems. Electrohydrodynamic (EHD) printing was employed to fill micro-reservoirs with controlled amount of drugs in the range of a few hundreds of picograms to tens of micrograms with spatial resolution of as small as 20 µm. Unlike most EHD systems, this system was configured in combination with an inverted microscope that allows in situ targeting of drug loading at micrometer scale accuracy. Methylene blue and rhodamine B were used as model drugs in distilled water, isopropanol and a polymer solution of a biodegradable polymer and dimethyl sulfoxide (DMSO). Also tetracycline-HCl/DI water was used as actual drug ink. The optimal parameters of EHD printing to load an extremely small quantity of drug into microscale drug reservoirs were investigated by changing pumping rates, the strength of an electric field and drug concentration. This targeted EHD technique was used to load drugs into the microreservoirs of PDMS microfluidic drug delivery devices and their drug release performance was demonstrated in vitro.

Advances in drug delivery via electrospun and electrosprayed nanomaterials

Electrohydrodynamic (EHD) techniques refer to procedures that utilize electrostatic forces to fabricate fibers or particles of different shapes with sizes in the nano-range to a few microns through electrically charged fluid jet. Employing different techniques, such as blending, surface modification, and coaxial process, there is a great possibility of incorporating bioactive such molecules as drugs, DNA, and growth factors into the nanostructures fabricated via EHD techniques. By careful selection of materials and processing conditions, desired encapsulation efficiency as well as preserved bioactivity of the therapeutic agents can be achieved. The drug-loaded nanostructures produced can be applied via different routes, such as implantation, injection, and topical or oral administration for a wide range of disease treatment. Taking advantage of the recent developments in EHD techniques like the coaxial process or multilayered structures, individually controlled delivery of multiple drugs is achievable, which is of great demand in cancer therapy and growth-factor delivery. This review summarizes the most recent techniques and postmodification methods to fabricate electrospun nanofibers and electrosprayed particles for drug-delivery applications.

Solution processed fabrication of single wall carbon nanotubes thin film by electrohydrodynamic atomization deposition technique and its characterization

An effective method for the fabrication of thin film of single wall carbon nanotubes (SWCNT) using the electro-hydrodynamic atomization (EHDA) deposition technique was demonstrated. In this study, the SWCNT aqueous based dispersion ink was subjected to electrostatic atomization by using an EHDA deposition system. The ink flow visualization under the influence of electric field was performed and the operating EHDA parametric envelope of the ink was explored. Then the deposition of SWCNT through the EHDA process was carried out onto a metallic substrate at a fixed flow rate and corresponding applied voltage thereby achieving thickness ranging from ∼70 to 130 nm by making multiple deposition passes. The microscopic inspection of the film was performed and thin film quality was examined by scanning electron microscope analysis. Finally, electrical behavior of the SWCNT film onto a metallic substrate through temperature dependent current-voltage measurements was investigated. The SWCNT film deposited onto the metallic substrate showed electrical conductivity of ∼2.98 S/cm.

Chitosan Coated Alginate Microparticles for Oral Vaccine Delivery

The aim of this study was to prepare Caalginate and chitosan (CS)Caalginate microparticles for peroral delivery of ovalbumin (OVA). Microparticles containing different loading of OVA (10, 20 and 40 % w/w) were prepared by cross-linking alginate with calcium chloride using an electrohydrodynamic spraying technique, and then coated with CS. The particle sizes of OVA-loaded microparticles were in the range of 1-5 µm. The negative charge was obtained for Caalginate microparticles (-14±1.9 mV) whereas CSCaalginate microparticles were positive charge (+6.06±3.4 mV). Caalginate microparticles with initial 20% w/w OVA showed the highest entrapment efficiency and amount of OVA content (24.91±0.4% and 33.22±0.1 mg/g, respectively) as similar to CSCaalginate microparticles with initial 20% w/w OVA that showed the highest entrapment efficiency and amount of OVA content (35.74±0.1% and 10.35±0.5 mg/g, respectively). It was found that the release rate of OVA from Caalginate microparticles was higher than CSCaalginate microparticles, and the lowest release rate, sustained release for 24 h, was found in the initial 40% w/w OVA. This study revealed that CSCaalginate microparticles have a considerable potential as controlled release antigen delivery systems.

Electrohydrodynamic atomization deposition and patterning of a carbon nano-suspension

In this paper, a 6 wt% carbon nano-suspension was prepared and atomized using electrohydrodynamic atomization technique. The different atomization modes at certain regions of working parameters (applied voltage and flow rate) were studied. In the stable cone-jet mode, the effect of the working distance (distance between needle exit and substrate) on the size and distribution of the deposited relics was examined. It was observed that higher working distance resulted in larger size and higher number density of relics, mainly at the range of 0.2–0.4 µm. A continuous carbon line with the width of ~50 µm was also print-patterned using the electrohydrodynamic atomization deposition technique from the carbon nano-suspension.

Development of Chitosan Nanoparticles for Gene Delivery Using Electrohydrodynamic Spraying Techniques

Chitosan nanoparticles were prepared by crosslinking chitosan (CS) with tripolyphosphate (TPP) solution using electrohydrodynamic spraying technique. The effects of CS and TPP concentration as well as electrical potential on particle size and shape were investigated. Appropriated formulations for preparing nanoparticles were chosen to encapsulate DNA. In vitro evaluation of the obtained nanoparticles as gene carrier such as entrapment efficiency and DNA release was performed. The results showed that 2 mg/ml TPP was dropped at 10 kV into 1 mg/ml CS (MW 20 kDa (F1) and 200 kDa (F2)) yielded the spherical shape and small particles of 227.67 and 240.33 nm, respectively. In DNA entrapment study, all formulations were tested by altering DNA loading to 10, 25 and 50 mg/g of CS. The results revealed that F1 with initial DNA 10 mg/g of CS showed the highest entrapment efficiency of 95.31%. While F2 with initial DNA of 25 mg/g of CS showed the highest entrapment efficiency of 89.16%. The DNA release study from CS nanoparticles indicated that the increasing of DNA amount slowed down the release rate. F1 and F2 with the initial DNA of 10 mg/g of CS had faster release rate than those with 25 and 50 mg/g of CS. It can be concluded that F1 yielded the nanoparticles with the smallest size, high DNA entrapment efficiency and enabled DNA sustained release.