Biomolecular interactions control the shape of stains from drying droplets of complex fluids

When a sessile droplet of a complex fluid dries, a stain forms on the solid surface. The structure and pattern of the stain can be used to detect the presence of a specific chemical compound in the sessile droplet. In the present work, we investigate what parameters of the stain or its formation can be used to characterize the specific interaction between an aqueous dispersion of beads and its receptor immobilized on the surface. We use the biotin-streptavidin system as an experimental model. Clear dissimilarities were observed in the drying sequences on streptavidin-coated substrates of droplets of aqueous solutions containing biotin-coated or streptavidin-coated beads. Fluorescent beads are used in order to visualize the fluid flow field. We show differences in the distribution of the particles on the surface depending on biomolecular interactions between beads and the solid surface. A mechanistic model is proposed to explain the different patterns obtained during drying. The model describes that the beads are left behind the receding wetting line rather than pulled towards the drop center if the biological binding force is comparable to the surface tension of the receding wetting line. Other forces such as the viscous drag, van der Waals forces, and solid–solid friction forces are found negligible. Simple microfluidics experiments are performed to further illustrate the difference in behavior where is adhesion or friction are present between the bead and substrate due to the biological force. The results of the model are in agreement with the experimental observations which provide insight and design capabilities. A better understanding of the effects of the droplet–surface interaction on the drying mechanism is a crucial first step before the identification of drying patterns can be promisingly applied to areas such as immunology and biomarker detection

Experimental Investigation and Data-Driven Analysis of Binary and Multi-Component Droplet Evaporation

Sessile droplet evaporation is an omnipresent phenomenon both in nature and technologies such as biodiagnostics, microfabrication, inkjet printing, spray cooling, and agriculture irrigation. Evolution of single component sessile droplets has been extensively studied under various parameters. However, in real applications, sessile droplets usually consist of two or more components. It has been shown that the environmental conditions such as humidity and temperature substantially change the behavior of sessile droplets. The strong tendency of organic fluids to absorb water is an important factor in evaporation of these fluids in humid environment. The water vapor present in the surrounding adsorbs/absorbs and possibly condenses into the droplet transforming the droplet into a binary system. While the humidity of surrounding is typically an imposed condition resulting in unwanted effects for many industries, we have proposed that these undesired effects can be controlled and eliminated by tuning the temperature of the substrate. We have studied the combined effect of relative humidity of surrounding and substrate temperature on evaporation of methanol droplets. Our results demonstrated that the diffusion of water into the droplet can be limited by changing temperature of the substrate by both shortening the lifetime of droplet or increasing the temperature of the liquid-gas interface above the due point. Additionally, we have developed machine learning, classification and regression, models to analyze the behavior of droplet under different conditions. We have shown that the regime of droplet evaporation can be accurately classified by analyzing the profile of the evolution of droplet macroscopic parameters. We have also demonstrated that the humidity of surrounding can be accurately estimated by analysis of droplet profile. Furthermore, the time evolution of diameter and contact angle are estimated by the regression model. As the number of components in the droplet increases, the underlying mechanisms become more complex. The proposed approach to analyze the dynamics of sessile droplet evaporation through data-driven techniques opens up ways to better understand the complicated physics behind multi-component droplet evaporation and in general intricate interfacial fluid mechanics problems. The combined effect of surrounding humidity and substrate temperature has been experimentally studied on the behavior of ternary droplet consisting of methanol, anise oil, and water. The simultaneous optical microscopy and infrared thermography revealed different mechanisms in the droplet such as hydrothermal waves, oil microdroplet nucleation, etc. Our results showed three stages in the evolution of hydrothermal waves during droplet lifetime. The experimental procedures and results in this work introduce easy and inexpensive method to control sessile droplet behavior which are crucial for the final product resolution in numerous applications

Osteoid osteoma of distal phalanx: A rare disorder and review of literature

Osteoid osteomata are rarely found in the distal phalanges of the hand. The usual presenting features are chronic pain, nail enlargement and increase in size of the terminal part of the digit. Diagnosis is difficult but surgical excision is effective for treating the patients′ pain. We reported this tumor in distal phalanx of the middle finger

Thermal efficiency enhancement of parabolic trough receivers using synthesized graphene oxide/SiO2 nanofluid and a rotary turbulator

Enhancing the thermal efficiency of parabolic solar collectors is still a challenging issue. In this study, two strategies including using nanofluid and a rotary turbulator are applied to ameliorate thermal efficiency. Here, graphene oxide/SiO2 nanofluids are fabricated in different concentrations and their thermophysical properties are measured. Subsequently, a numerical model is carried out to study the influence of applying nanofluid and the rotary turbulator on thermal efficiency. The results indicate that using nanofluid leads to a 9% increase in thermal efficiency and adding the turbulator enhances thermal efficiency by more than 20%. Although hydraulic analysis reveals the Performance Evaluation Criteria remains in an acceptable range, the friction factor and Nusselt number increase by the addition of nanoparticles to the basefluid

Biomolecular interactions control the shape of stains from drying droplets of complex fluids

When a sessile droplet of a complex fluid dries, a stain forms on the solid surface. The structure and pattern of the stain can be used to detect the presence of a specific chemical compound in the sessile droplet. In the present work, we investigate what parameters of the stain or its formation can be used to characterize the specific interaction between an aqueous dispersion of beads and its receptor immobilized on the surface. We use the biotin-streptavidin system as an experimental model. Clear dissimilarities were observed in the drying sequences on streptavidin-coated substrates of droplets of aqueous solutions containing biotin-coated or streptavidin-coated beads. Fluorescent beads are used in order to visualize the fluid flow field. We show differences in the distribution of the particles on the surface depending on biomolecular interactions between beads and the solid surface. A mechanistic model is proposed to explain the different patterns obtained during drying. The model describes that the beads are left behind the receding wetting line rather than pulled towards the drop center if the biological binding force is comparable to the surface tension of the receding wetting line. Other forces such as the viscous drag, van der Waals forces, and solid–solid friction forces are found negligible. Simple microfluidics experiments are performed to further illustrate the difference in behavior where is adhesion or friction are present between the bead and substrate due to the biological force. The results of the model are in agreement with the experimental observations which provide insight and design capabilities. A better understanding of the effects of the droplet–surface interaction on the drying mechanism is a crucial first step before the identification of drying patterns can be promisingly applied to areas such as immunology and biomarker detection.NOTICE: this is the author’s version of a work that was accepted for publication in Chemical Engineering Science. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Chemical Engineering Science, [137, (2015)] doi:10.1016/j.ces.2015.06.059</p

Discovering giant magnetoelasticity in soft matter for electronic textiles.

We discovered a giant magnetoelasticity in soft matter with up to 5-fold enhancement of magnetomechanical coupling factors compared to that of rigid metal alloys without an externally applied magnetic field. A wavy chain analytical model based on the magnetic dipole-dipole interaction and demagnetizing field was established, fitting well to the experimental observation. To explore its potentials in electronic textiles, we coupled it with magnetic induction to invent a textile magnetoelastic generator (MEG), a new working mechanism for biomechanical energy conversion, featuring an intrinsic waterproofness, an ultralow internal impedance of approximately 20 Ω, and a high short-circuit current density of 1.37 mA/cm2, which is about four orders of magnitude higher than that of other textile generator counterparts. Meanwhile, assisted by machine learning, the textile MEG could continuously monitor the respiratory activities on heavily perspiring skin without any encapsulation, allowing a timely diagnosis of the respiration abnormalities in a self-powered manner. We foresee that this discovery can be extended to wide-range soft-matter systems, emerging as a compelling approach to develop electronic textiles for energy, sensing, and therapeutic applications