Vasileios Koutsos - Academia.edu (original) (raw)

Papers by Vasileios Koutsos

Nanomanufacturing and Metrology

The morphology of linear polybutadiene physisorbed on freshly cleaved mica from a dilute polymer ... more The morphology of linear polybutadiene physisorbed on freshly cleaved mica from a dilute polymer solution is investigated through atomic force microscopy. A fine-structure study shows that the monolayer morphology in air (after rapid solvent evaporation) depends strongly on the molecular weight (Mw) of the linear polymer, the adsorbed amount, and the conformation adopted by the adsorbed polymer chains under good solvent conditions. The dependence of the observed polymer structure on Mw is most significant for samples with high surface density, where the intermolecular interactions among the adsorbed polymers are important. For high surface density, the adsorbed polymers tend to aggregate and minimize unfavorable contacts with air for all of the different Mw samples, leading to an isotropic structural pattern. These structural phenomena with increasing surface density are explained on the basis of the intermolecular interactions of the adsorbed polymers under good solvent conditions,...

Procedia IUTAM, 2015

Peer-review under the responsibility of the organizing committee of DYNACAPS 2014 (Dynamics of Ca... more Peer-review under the responsibility of the organizing committee of DYNACAPS 2014 (Dynamics of Capsules, Vesicles and Cells in Flow).

Additional file 7. All the STL files of the parts compressed.

Additional file 5. CAD drawing of the support stand part.

Journal of Applied Polymer Science, 2021

Fiber-metal laminates (FMLs) offer the superior characteristics of polymer composites (i.e., ligh... more Fiber-metal laminates (FMLs) offer the superior characteristics of polymer composites (i.e., light weight, high strength and stiffness) with the ductility and fracture strength of metals. The bond strength between the two dissimilar materials, composite and metal, dictates the properties and performance of the FMLs. The bonding becomes more critical when the polymer matrix is thermoplastic and hydrophobic in nature. This work employed a novel bonding technique between thermoplastic composites and a metal layer using six different combinations of organic coatings. The flexural, and interlaminar shear strength of the thermoplastic fiber metal laminates (TP-FMLs) were examined to investigate the bond strengths in the different cases along with fracture characteristics revealed from the tested samples using scanning electron microscopy. The viscoelastic performance of the fabricated TP-FMLs were also investigated using the dynamic mechanical thermal analysis method.

Bulletin of the American Physical Society, 2018

Take-down policy If you believe that this document breaches copyright please contact us providing... more Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.

Concrete is the most consumed construction material in the world. The cement production contribut... more Concrete is the most consumed construction material in the world. The cement production contributes around 5% of CO2 emissions globally. Due to this substantial production, conventional resource supplies are in decline. This unsustainable supply has prompted a paradigm shift towards alternative raw materials to reduce the consumption of conventional concrete constituents and produce 'green concrete'. One of the most effective ways is to replace cement with pozzolans derived from industry wastes, such as ceramic. Ceramics are the single largest contributor to construction and demolition waste globally, 54% in 2014 alone. There are approximately 68 million tonnes of ceramic waste sent to landfills annually in the UK. Current research into utilizing ceramics waste as a potential pozzolanic material in the production of 'green concrete' has had promising results. This study investigates the feasibility of using recycled ceramic waste in order to produce high performance concrete, while simultaneously reducing the consumption of cement. In this project, the mechanical performance of cement mortar samples, with a 15 % ceramic-cement replacement by weight was analysed and discussed. Further, the chemical properties of the concrete samples were determined using Xray Powder Diffraction and the results were correlated with the mechanical strength tests. This study shows that ceramic waste of UK source can be a promising cement replacement to produce "green concrete".

Bulletin of the American Physical Society, 2019

Submitted for the DFD19 Meeting of The American Physical Society Evaporation of sessile drops on ... more Submitted for the DFD19 Meeting of The American Physical Society Evaporation of sessile drops on soft membranes with capillary origami 1 YUHONG CHEN, DANIEL OREJON, PRASHANT VALLURI, VASILEIOS KOUTSOS, KHELLIL SEFIANE, the University of Edinburgh-Drops evaporating on soft substrates are common in nature, such as raindrops on tree leaves. If the substrate is thin enough, it can get folded by the action of surface tension of a drying drop. This folding is known as 'capillary origami', which provides a simple and cheap method for fabricating predetermined 3D structures at the micro/nano-scale. Here, we explore the influence of capillary origami on drop evaporation. Our experiments concern with evaporation of sessile microliter water drops on soft PDMS membranes. We consider the effect of substrate thickness noting that bending stiffness is a cubic function of thickness. Thus, drying sessile droplets of the same size can lead to either absent, partial or complete folding of the substrate. The evolution of evaporation fluxes is obtained through a microbalance with a resolution of 0.01 mg. Simultaneously the profiles of drops and membranes are recorded by a side-view CCD camera and a top-view optical camera, respectively. These videos are processed using ImageJ to extract the data and quantify the folding extent of the membranes. Our results show that foldable membranes reduce evaporation rates of sessile droplets thereby lengthening the drop lifetimes.

Energies, 2021

Plastics are versatile materials used in a variety of sectors that have seen a rapid increase in ... more Plastics are versatile materials used in a variety of sectors that have seen a rapid increase in their global production. Millions of tonnes of plastic wastes are generated each year, which puts pressure on plastic waste management methods to prevent their accumulation within the environment. Recycling is an attractive disposal method and aids the initiative of a circular plastic economy, but recycling still has challenges to overcome. This review starts with an overview of the current European recycling strategies for solid plastic waste and the challenges faced. Emphasis lies on the recycling of polyolefins (POs) and polyethylene terephthalate (PET) which are found in plastic packaging, as packaging contributes a signification proportion to solid plastic wastes. Both sections, the recycling of POs and PET, discuss the sources of wastes, chemical and mechanical recycling, effects of recycling on the material properties, strategies to improve the performance of recycled POs and PET,...

Development of wearable sensing platforms is essential for the advancement of continuous health m... more Development of wearable sensing platforms is essential for the advancement of continuous health monitoring and point-of-care testing. Eccrine sweat pH is an analyte that can be noninvasively measured and used to diagnose and aid in monitoring a wide range of physiological conditions. Surface-enhanced Raman scattering (SERS) offers a rapid, optical technique for fingerprinting of biomarkers present in sweat. In this paper, a mechanically flexible, nanofibrous, SERS-active substrate was fabricated by a combination of electrospinning of thermoplastic polyurethane (TPU) and Au sputter coating. This substrate was then investigated for suitability toward wearable sweat pH sensing after functionalization with two commonly used pH-responsive molecules, 4-mercaptobenzoic acid (4-MBA), and 4-mercaptopyridine (4-MPy). The developed SERS pH sensor was found to have good resolution (0.14 pH units for 4-MBA; 0.51 pH units for 4-MPy), with only 1 μL of sweat required for a measurement, and displayed no statistically significant difference in performance after 35 days (p = 0.361). Additionally, the Au/TPU nanofibrous SERS pH sensors showed fast sweat-absorbing ability as well as good repeatability and reversibility. The proposed methodology offers a facile route for the fabrication of SERS substrates which could also be used to measure a wide range of health biomarkers beyond sweat pH.

Pharmaceutics, 2021

Nanofibers of the poorly water-soluble antibiotic ciprofloxacin (CIP) were fabricated in the form... more Nanofibers of the poorly water-soluble antibiotic ciprofloxacin (CIP) were fabricated in the form of an amorphous solid dispersion by using poly(vinyl pyrrolidone) as a polymer matrix, by the low-cost electrospinning method. The solubility of the nanofibers as well as their in vitro diffusion were remarkably higher than those of the CIP powder or the physical mixture of the two components. The fiber size and morphology were optimized, and it was found that the addition of the CIP to the electrospinning solution decreased the nanofiber diameter, leading to an increased specific surface area. Structural characterization confirmed the interactions between the drug and the polymer and the amorphous state of CIP inside the nanofibers. Since the solubility of CIP is pH-dependent, the in vitro solubility and dissolution studies were executed at different pH levels. The nanofiber sample with the finest morphology demonstrated a significant increase in solubility both in water and pH 7.4 buf...

Sustainability, 2020

4D printing can be defined as the fabrication of structures using smart materials that allow the ... more 4D printing can be defined as the fabrication of structures using smart materials that allow the final object to change its shape, properties, or function in response to an external stimulus such as light, heat, or moisture. The available technologies, materials, and applications have evolved significantly since their first development in 2013, with prospective applications within the aerospace, manufacturing, and soft robotic industries. This review focuses on the printing technologies and smart materials currently available for fabricating these structures. The applications of 4D printing within biomedicine are explored with a focus on tissue engineering, drug delivery, and artificial organs. Finally, some ideas for potential uses are proposed. 4D printing is making its mark with seemingly unlimited potential applications, however, its use in mainstream medical treatments relies on further developments and extensive research investments.

Medical Engineering & Physics, 2021

There is a high demand for small diameter vascular grafts having mechanical and biological proper... more There is a high demand for small diameter vascular grafts having mechanical and biological properties similar to that of living tissues. Tissue-engineered vascular grafts using current methods have often failed due to the mismatch of mechanical properties between the implanted graft and living tissues. To address this limitation, a hybrid bioprinting-electrospinning system is developed for vascular tissue engineering applications. The setup is capable of producing layered structure from electrospun fibres and cell-laden hydrogel. A Creality3D Ender 3D printer has been modified into a hybrid setup having one bioprinting head and two electrospinning heads. Fortus 250mc and Flashforge Creator Pro 3D printers were used to print parts using acrylonitrile butadiene styrene (ABS) and polylactic acid (PLA) polymers. An Arduino mega 2560 and a Ramps 1.4 controller board were selected to control the functions of the hybrid bioprinting setup. The setup was tested successfully to print a tubular construct around a rotating needle.

Biofabrication, 2021

Recent advancements in the bioinks and three-dimensional (3D) bioprinting methods used to fabrica... more Recent advancements in the bioinks and three-dimensional (3D) bioprinting methods used to fabricate vascular constructs are summarized herein. Critical biomechanical properties required to fabricate an ideal vascular graft are highlighted, as well as various testing methods have been outlined to evaluate the bio-fabricated grafts as per the Food and Drug Administration (FDA) and International Organization for Standardization (ISO) guidelines. Occlusive artery disease and cardiovascular disease are the major causes of death globally. These diseases are caused by the blockage in the arteries, which results in a decreased blood flow to the tissues of major organs in the body, such as the heart. Bypass surgery is often performed using a vascular graft to re-route the blood flow. Autologous grafts represent a gold standard for such bypass surgeries; however, these grafts may be unavailable due to the previous harvesting or possess a poor quality. Synthetic grafts serve well for medium to...

Polymers, 2021

Aramid fibers are high-strength and high-modulus technical fibers used in protective clothing, su... more Aramid fibers are high-strength and high-modulus technical fibers used in protective clothing, such as bulletproof vests and helmets, as well as in industrial applications, such as tires and brake pads. However, their full potential is not currently utilized due to adhesion problems to matrix materials. In this paper, we study how the introduction of mechanical adhesion between aramid fibers and matrix material the affects adhesion properties of the fiber in both thermoplastic and thermoset matrix. A microwave-induced surface modification method is used to create nanostructures to the fiber surface and a high throughput microbond method is used to determine changes in interfacial shear strength with an epoxy (EP) and a polypropylene (PP) matrix. Additionally, Fourier transform infrared spectroscopy, atomic force microscopy, and scanning electron microscopy were used to evaluate the surface morphology of the fibers and differences in failure mechanism at the fiber-matrix interface. W...

Sensors, 2021

The addition of piezoelectric zinc oxide (ZnO) fillers into a flexible polymer matrix has emerged... more The addition of piezoelectric zinc oxide (ZnO) fillers into a flexible polymer matrix has emerged as potential piezocomposite materials that can be used for applications such as energy harvesters and pressure sensors. A simple approach for the fabrication of PDMS-ZnO piezoelectric nanocomposites based on two ZnO fillers: nanoparticles (NP) and nanoflowers (NF) is presented in this paper. The effect of the ZnO fillers’ geometry and size on the thermal, mechanical and piezoelectric properties is discussed. The sensors were fabricated in a sandwich-like structure using aluminium (Al) thin films as top and bottom electrodes. Piezocomposites at a concentration of 10% w/w showed good flexibility, generating a piezoelectric response under compression force. The NF piezocomposites showed the highest piezoelectric response compared to the NP piezocomposites due to their geometric connectivity. The piezoelectric compound NF generated 4.2 V while the NP generated 1.86 V under around 36 kPa pre...