Ali Dhinojwala

Ali Dhinojwala
University of Akron · Department of Polymer Science

PhD

About

304
Publications
45,439
Reads
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7,880
Citations
Citations since 2016
122 Research Items
4446 Citations
20162017201820192020202120220200400600800
20162017201820192020202120220200400600800
20162017201820192020202120220200400600800
20162017201820192020202120220200400600800
Additional affiliations
August 1997 - present
University of Akron
Position
  • H. A. Morton Professor

Publications

Publications (304)
Article
Microscopic papillae on polar bear paw pads are considered adaptations for increased friction on ice/snow, yet this assertion is based on a single study of one species. The lack of comparative data from species that exploit different habitats renders the ecomorphological associations of papillae unclear. Here, we quantify the surface roughness of t...
Article
We correlate the strength of interfacial interactions with the adhesive force necessary to separate a polymer from a surface. It is intuitive that interactions would influence adhesion and friction; however, challenges in the direct measurement of the interaction strength at interfaces have obscured the connection between these interactions and suc...
Preprint
Full-text available
Inspired by structural colors in avian species, various synthetic strategies have been developed to produce non-iridescent, saturated colors using nanoparticle assemblies. Mixtures of nanoparticles varying in particle chemistry (or complex refractive indices) and particle size have additional emergent properties that impact the color produced. For...
Article
Bright, saturated structural colors in birds have inspired synthesis of self-assembled, disordered arrays of assembled nanoparticles with varied particle spacings and refractive indices. However, predicting colors of assembled nanoparticles, and thereby guiding their synthesis, remains challenging due to the effects of multiple scattering and stron...
Article
Friction is one of the leading causes of energy loss in moving parts, and understanding how roughness affects friction is of utmost importance. From creating surfaces with high friction to prevent slip and movement, to creating surfaces with low friction to minimize energy loss, roughness plays a key role. By measuring shear stresses of crosslinked...
Article
Spider aggregate glue can absorb moisture from the atmosphere to reduce its viscosity and become tacky. The viscosity at which glue adhesion is maximized is remarkably similar across spider species, even though that viscosity is achieved at very different relative humidity (RH) values matching their diverse habitats. However, the molecular changes...
Article
The subdigital adhesive pads of Caribbean Anolis lizards are considered to be a key innovation that permits occupation of novel ecological niches. Although previous work has demonstrated that subdigital pad morphology and performance vary with habitat use, such investigations have only considered the macroscale aspects of these structures (e.g. pad...
Article
Full-text available
The roughness and wettability of surfaces exploited by free-ranging geckos can be highly variable and attachment to these substrates is context dependent (e.g., presence or absence of surface water). Although previous studies focus on the effect of these variables on attachment independently, geckos encounter a variety of conditions in their natura...
Article
Full-text available
We present a new open-source, machine learning (ML) enhanced computational method for experimentalists to quickly analyze high-throughput small-angle scattering results from multicomponent nanoparticle mixtures and solutions at varying compositions and concentrations to obtain reconstructed 3D structures of the sample. This new method is an improve...
Preprint
Full-text available
Bright, saturated structural colors in birds have inspired synthesis of self-assembled, disordered arrays of colloidal particles with varied particle spacings and refractive indices. However, predicting colors of assembled colloidal particles, and thereby guiding their synthesis, remains challenging due to the effects of multiple scattering and str...
Chapter
Polymer interfaces control many properties such wetting, adsorption, adhesion, friction, and mechanical properties, and understanding interfacial interactions has remained of central importance for years. In this chapter, we discuss the measurements of interfacial interactions (van der Waals and ”polar” acid–base) by measuring shifts in hydrogen bo...
Article
Melanin is a ubiquitous natural pigment that exhibits broadband absorption and high refractive index. Despite its widespread use in structural color production, how the absorbing material, melanin, affects the generated color is unknown. Using a combined molecular dynamics and finite-difference time-domain computational approach, this paper investi...
Article
Full-text available
Melanin, a widespread pigment found in many taxa, is widely recognized for its high refractive index, ultraviolet (UV) protection, radical quenching ability, metal binding, and many other unique properties. The aforementioned characteristic traits make melanin a potential candidate for biomedical, separation, structural coloration, and space applic...
Preprint
Full-text available
Melanin is a ubiquitous natural pigment that exhibits broadband absorption and high refractive index. Despite its widespread use in structural color production, how the absorbing material, melanin, affects the generated color is unknown. Using a combined molecular dynamics and finite-difference time-domain computational approach, this paper investi...
Article
Full-text available
Water and adhesives have a conflicting relationship as demonstrated by the failure of most man-made adhesives in underwater environments. However, living creatures routinely adhere to substrates underwater. For example, sandcastle worms create protective reefs underwater by secreting a cocktail of protein glue that binds mineral particles together,...
Article
Significance Understanding underwater contact mechanics between soft materials and hard surfaces is of prime importance due to its ubiquity and practical relevance. From biological creatures climbing on flooded surfaces and human figures getting grip on wet surfaces to adhesives sealing a wound underwater, performance depends upon water evacuation...
Preprint
Full-text available
When adhesive elastomeric materials slide over hard rough surfaces at low velocities, there are two primary dissipative mechanisms that control how friction changes with sliding velocity: viscoelastic dissipation and adhesive dissipation. To distinguish the contribution of these dissipative mechanisms we have measured frictional shear stresses for...
Article
Full-text available
Silica aerogels are interesting porous materials with extremely low density and high surface area, making them advantageous for a number of aerospace and catalysis applications. Here, we report the preparation of polydopamine (PDA)-functionalized silica aerogels using an in situ coating method, wherein the dopamine monomer was allowed to diffuse th...
Article
The diverse colours of bird feathers are produced by both pigments and nanostructures, and can have substantial thermal consequences. This is because reflectance, transmittance and absorption of differently coloured tissues affect the heat loads acquired from solar radiation. Using reflectance measurements and heating experiments on sunbird museum...
Article
Full-text available
Mussels, which are marine creatures, stick strongly to various substrates underwater using foot proteins rich in amino acids like L-3,4-dihydroxyphenylalanine (DOPA). This stimulates the synthesis of catechol-containing polymers that possess strong underwater adhesion; consequently, the mechanism is ascribed solely to catechol functionality. Howeve...
Article
The spider major ampullate (MA) silk exhibits high tensile strength and extensibility and is typically a blend of MaSp1 and MaSp2 proteins with the latter comprising glycine–proline–glycine–glycine-X repeating motifs that promote extensibility and supercontraction. The MA silk from Darwin's bark spider ( Caerostris darwini ) is estimated to be two...
Patent
Full-text available
In one or more embodiments, the present invention provides a method of applying or printing structural colors to a substrate that involves pre-treatment of the substrate surface to prevent absorption of the fluid containing the particles. This allows the fluid to maintain their sessile drop shapes and as the water evaporates, the colloidal particle...
Article
A single layer of graphene when transferred to a solid substrate has the ability to screen or transmit interactions from the underlying substrate, which has direct consequences in applications of this 2D material to flexible electronics and sensors. Previous reports using a multitude of techniques present contradictory views on graphene's ability t...
Article
Full-text available
While it is generally accepted that van der Waals (vdW) forces govern gecko adhesion, several studies indicate contributions from non-vdW forces and highlight the importance of understanding the adhesive contact interface. Previous work hypothesized that the surface of gecko setae is hydrophobic, with nonpolar lipid tails exposed on the surface. Ho...
Article
Spider viscid silk adheres to insects in orb webs and is a "smart-adhesive" that quickly changes droplet size, viscosity, and adhesiveness in response to atmospheric humidity. Different species of spiders "tune" water uptake to match the humidity of their foraging environments, achieving a similar "universal" viscosity that optimizes tradeoffs in s...
Preprint
Full-text available
Thermodynamics tells us to expect underwater contact between two hydrophobic surfaces to result in stronger adhesion compared to two hydrophilic surfaces. However, presence of water changes not only energetics, but also the dynamic process of reaching a final state, which couples solid deformation and liquid evacuation. These dynamics can create ch...
Preprint
p>A single layer of graphene when transferred to a solid substrate has the ability to screen or transmit interactions from the underlying substrate, which has direct consequences in applications of this 2D material to flexible electronics and sensors. Previous reports using a multitude of techniques present contradictory views on graphene’s ability...
Article
Melanin is ubiquitous in living organisms across different biological kingdoms of life, making it an important, natural biomaterial. Its presence in nature from microorganisms to higher animals and plants is attributed to the many functions of melanin, including pigmentation, radical scavenging, radiation protection, and thermal regulation. General...
Article
Gecko substrate use is likely influenced by adhesive performance, yet few studies have demonstrated this empirically. Herein we examine the substrate use, adhesive performance, and vertical clinging behaviour of Gekko gecko in captivity to investigate whether adhesive performance influences patterns of substrate use. We found that geckos were obser...
Chapter
Improvement in adhesion in wet environments serves as a potential avenue for enhancing numerous technologies. Understanding the adhesion between varying surface chemistry interfaces in the presence of water can aid in designing materials. Sum frequency generation spectroscopy (SFG) provides a unique opportunity to measure the presence of water at t...
Article
The functional morphology of squamate fibrillar adhesive systems has been extensively investigated and has indirectly and directly influenced the design of synthetic counter- parts. Not surprisingly, the structure and geometry of exemplar fibrils (setae) have been the subject of the bulk of the attention in such research, although variation in seta...
Article
Structurally colored supraparticles, formed from dispersed nanoparticle building blocks through self-assembly, have tremendous potential for applications in displays, coatings, paints, inks, and cosmetics. Mechanical stability and solvent compatibility of supraparticles is critical in these applications. Here, we describe the scalable synthesis of...
Article
Full-text available
Melanin, with its high refractive index (RI) and broadband absorption, is an important biomaterial responsible for many of the vibrant structural colors observed in nature and for UV protection. Even though the RI plays an important role in the function of melanin, there is an ambiguity in its reported complex RI and a lack of understanding of whet...
Preprint
Full-text available
The functional morphology of squamate fibrillar adhesive systems has been extensively investigated and has indirectly and directly influenced the design of synthetic counterparts. Not surprisingly, the structure and geometry of exemplar fibrils (setae) have been the subject of the bulk of the attention in such research, although variation in setal...
Article
The bacterium Caulobacter crescentus is known to attach irreversibly to underwater surfaces by utilizing an adhesive structure called the holdfast, which exhibits the highest adhesive strength known for any organism. The very small size of the holdfast (~ 400 nm wide and ~ 40 nm high) has made direct chemical analysis difficult, and its structure r...
Article
Molecular disordering of the ice surface occurs below the bulk melting temperature of 273 K, termed surface premelting. The top-most molecular layer begins gradually premelting at 200 K, and has been linked to its low coefficient of friction through an increase in molecular mobility. The second molecular bilayer premelts around 257 K, but no study...
Article
Melanin is a widespread multifunctional biological pigment that has emerged as a promising platform for applications in coating, catalysis, energy, drug delivery, and medical therapy. Melanin is also a compelling material for photonic applications because of its favorable material characteristics, including broadband absorption, high refractive ind...
Article
Full-text available
Melanins are a family of heterogeneous biopolymers found ubiquitously across plant, animal, bacterial, and fungal kingdoms where they act variously as pigments and as radiation protection agents. There exist five multifunctional yet structurally and biosynthetically incompletely understood varieties of melanin: eumelanin, neuromelanin, pyomelanin,...
Preprint
Full-text available
In a likely coevolutionary arms race, insects evolved a variety of counter strategies to avoid capture by spider webs, while spiders evolved innovations web structure and especially their adhesive silks. For instance, insect cuticles employ a variety of potential anti-adhesion mechanisms such as the detachable scales of moths and surface waxes and...
Article
Full-text available
To stop blood loss and accelerate wound healing, conventional wound closure techniques such as sutures and staples are currently used in the clinic. These tissue-piercing wound closure techniques have several disadvantages such as the potential for causing inflammation, infections, and scar formation. Surgical sealants and tissue adhesives can addr...
Preprint
Molecular disordering of the ice surface occurs below the bulk melting temperature of 273 K, termed surface premelting. The top-most molecular layer begins gradually premelting at 200 K, and has been linked to its low coefficient of friction through an increase in molecular mobility. The second molecular bilayer premelts around 257 K, but no study...
Article
Full-text available
Use of colloidal suspensions to generate structural colors has the potential to reduce the use of toxic metals or organic pigments in inkjet printing, coatings, cosmetics, and other applications, and is a promising avenue to create large-scale nanostructures that produce long-lasting colors. However, expanded use of structural colors requires a red...
Article
Melts of long-chain polar amphiphiles do not wet polar substrates (autophobic) due to the formation of a monolayer that lowers the surface energy of the substrate. The monolayer adsorbed onto the substrate melts at a temperature (Ts) much higher than the bulk melting temperature (Tm) on account of strong headgroup-substrate interactions. Contrary t...
Article
Use of a plasma polymerized (pp) layer under a polyurethane (PU) coating on aluminum dramatically improves the corrosion resistance provided. Compared to conventional polymer coatings, plasma polymerized coatings are more highly crosslinked, have better adhesion to substrates and result in lower emission of volatile organic contents (VOCs). While p...
Article
Full-text available
Contaminants decrease adhesive strength by interfering with substrate contact. Spider webs adhering to moths present an ideal model to investigate how natural adhesives overcome contamination because moths' sacrificial layer of scales rubs off on sticky silk, facilitating escape. However, Cyrtarachninae spiders have evolved gluey capture threads th...
Article
Melanins are macromolecules that are ubiquitous in nature and impart a large variety of biological functions, including structure, coloration, radiation resistance, free radical scavenging, and thermoregulation. Currently, in the majority of investigations, melanins are either chemically synthesized or extracted from animals, which presents signifi...
Article
Full-text available
The properties of nanoconfined water arise in direct response to the properties of the interfaces that confine it. A great deal of research has focused on understanding how and why the physical properties of confined water differ greatly from the bulk. In this work, we have used all-atom molecular dynamics (MD) simulations to provide a detailed des...
Article
Adhesive attachment systems consisting of multiple tapes or strands are commonly found in nature, for example in spider web anchorages or in mussel byssal threads, and their structure has been found to be ingeniously architected in order to optimize mechanical properties: in particular, to maximize dissipated energy before full detachment. These pr...
Article
Full-text available
A mechanistic understanding of adhesion in soft materials is critical in the fields of transportation (tires, gaskets, and seals), biomaterials, microcontact printing, and soft robotics. Measurements have long demonstrated that the apparent work of adhesion coming into contact is consistently lower than the intrinsic work of adhesion for the materi...
Article
Line-shape broadness in vibrational spectra is usually associated with structural heterogeneity of the surrounding environment. At the solid/liquid interface, surface-sensitive sum-frequency generation spectroscopy (SFG) has shown a variety of distributions of the vibrational frequency for sapphire surface hydroxyl groups in contact with several li...
Article
The remarkable properties of the gecko adhesive system have been intensively studied. Although many gecko-inspired synthetic adhesives have been designed and fabricated, few manage to capture the multifunctionality of the natural system. Analogous to previously documented self-cleaning, recent work demonstrated that gecko toe pads dry when geckos t...
Article
The competitive adsorption of molecules on a surface has both beneficial and detrimental effects for technological applications, such as chromatography (material separation) and protein adsorption on medical implants. A comprehensive understanding of adsorption can aid in the design of surfaces with desired functional properties. Molecular dynamics...
Article
Eumelanin is a ubiquitous natural pigment that has a broad absorption across ultraviolet (UV, 100-400 nm) and visible wavelengths (400-700 nm), and can protect against radiation. Synthetic eumelanin with properties similar to natural eumelanin has been made using dopamine or dihydroxyindole (DHI). Here, we use solid-state nuclear magnetic resonance...
Preprint
Inspired from the one-component self-coacervation of tropoelastin and mussel foot protein-3s, we created the first non-ionic, single component coacervates that can coacervate in a all ranges of pH (acidic to basic) and wide range of ionic strengths with degradability, rapid curing and strong underwater adhesion. In contrast to the complex coacervat...
Article
Full-text available
Surface segregation in binary colloidal mixtures offers a simple way to control both surface and bulk properties without affecting their bulk composition. Here, we combine experiments and coarse-grained molecular dynamics (CG-MD) simulations to delineate the effects of particle chemistry and size on surface segregation in photonic colloidal assembl...
Article
Chlorophyll (Chl) f and d are the most recently discovered chlorophylls, enabling cyanobacteria to harvest near infrared radiation (NIR) at 700‐780 nm for oxygenic photosynthesis. Little is known about the occurrence of these pigments in terrestrial habitats. Here we provide first details on spectral photon irradiance within the photic zones of fou...
Preprint
Full-text available
Contaminants decrease adhesive strength by interfering with substrate contact. Spider webs adhering to moths present an ideal model to investigate how natural adhesives overcome contamination because moths’ sacrificial layer of scales rub off on sticky silk, facilitating escape. The Cyrtarachninae spiders are moth-specialists that evolved gluey cap...
Article
Interfacial interactions govern a number of macroscopic behaviors including adsorption and self-assembly. Acid-base interactions have been previously shown to comprise a significant portion of the interaction strength for polar liquids in contact with high-energy solids. Previous studies using interface-sensitive sum frequency generation spectrosco...
Article
Full-text available
Background: Mucus and mucus glands are important features of the amphibian cutis. In tree frogs, the mucus glands and their secretions are crucial components of the adhesive digital pads of these animals. Despite a variety of hypothesised functions of these components in tree frog attachment, the functional morphology of the digital mucus glands an...
Article
Clinically used bio-based tissue sealants bring in the risk of animal borne infections, non-degradability, allergic reactions, tissue compression, tissue necrosis, and poor wet adhesion. Motivated by these unsatisfactory properties of existing tissue sealants, herein, we designed a library of solvent- and initiator- free hydrophobic mussel-inspired...
Article
Full-text available
Nanostructured materials producing structural colors have a great potential in replacing toxic metals or organic pigments. Electrophoretic deposition (EPD) is a promising method for producing these materials in a large scale, but it requires improvements in brightness, saturation, and mechanical stability. Herein we use EPD assembly to co-deposit s...