Patrick T. Spicer

Patrick T. Spicer
UNSW Sydney | UNSW · School of Chemical Engineering

PhD

About

90
Publications
7,686
Reads
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3,485
Citations
Introduction
After 15 years with P&G, Pat began work as an Associate Professor of Chemical Engineering at the University of New South Wales in Sydney, Australia in 2012. There his research focuses on the design and development of microstructured fluid materials by understanding their kinetic behavior. His areas of focus in the field include the understanding of particle shape effects on materials performance and interactions of soft matter with biological systems.
Additional affiliations
December 2012 - present
UNSW Sydney
Position
  • Professor (Associate)
December 1997 - October 2012
Procter & Gamble
Position
  • Section Head - Complex Fluid Development and Processing
Education
September 1992 - September 1997
University of Cincinnati
Field of study
  • Chemical Engineering
September 1987 - June 1992
University of Delaware
Field of study
  • Chemical Engineering

Publications

Publications (90)
Article
Full-text available
Grass pollens have been identified as mediators of respiratory distress, capable of exacerbating respiratory diseases including epidemic thunderstorm asthma (ETSA). It is hypothesised that during thunderstorms, grass pollen grains swell to absorb atmospheric water, rupture, and release internal protein content to the atmosphere. The inhalation of a...
Article
Bacterial cellulose biofilms are complex networks of strong interwoven nanofibers that control transport and protect bacterial colonies in the film. The design of diverse applications of these bacterial cellulose films also relies on understanding and controlling transport through the fiber mesh, and transport simulations of the films are most accu...
Preprint
Full-text available
Bacterial cellulose biofilms are complex networks of strong entangled nanofibers that control transport and protect bacterial colonies in the film. Design of diverse applications of bacterial cellulose films also relies on understanding and controlling transport through the fiber mesh, and transport simulations of the films are most accurate when g...
Article
Hypothesis A micron-scale oil-in-water emulsion droplet frozen in the presence of surfactants can be induced to eject the crystallizing solid from its liquid precursor. This dynamic process produces highly elongated solids whose shape depends critically on the rate of crystallization and the interfacial properties of the tri-phase system. Experime...
Article
Microscopic high aspect ratio particles have many applications including enhanced delivery of active ingredients and food stability. Here, we develop a simple, scalable process that produces particles with a continuously controllable aspect ratio. Oil-in-water emulsion droplets are quenched and crystallize in the presence of surfactants that facili...
Article
Chemical engineers are well positioned to design and manufacture formulated liquid products, but formulated product design is not often taught in a unified way.
Article
Arrested, or partial, coalescence of viscoelastic emulsion droplets can occur when elastic resistance to deformation offsets droplet surface area minimization. Arrest is a critical element of food and consumer product microstructure and performance, but direct studies of structural arrest and rearrangement have been carried out using only two or th...
Article
We explore the flow behavior of concentrated emulsions for which the viscosity of the continuous phase can be significantly varied by changing the temperature. The exponents obtained by fitting the shear rate-dependent stress with the popular Herschel–Bulkley (HB) model display a systematic dependence on the viscosity of the continuous phase, revea...
Article
Full-text available
Wearable fabrics are predominantly produced from synthetic polymer fibers derived from petrochemicals. These have negative effects on the natural environment as a consequence of the manufacturing process, insurmountable waste production, and persistence of the fibers in ecosystems. With the use of wearables worldwide set to increase exponentially,...
Article
Control of particle shape is of increased interest, as it can broaden the versatility of dispersed material applications. The design of targeted and selective response, such as shape-change, in synthetic materials offers an opportunity to mimic and understand biophysical motion, but also enhance commercial active material delivery. Although solids...
Article
Full-text available
Correction for ‘Comparison of bulk and microfluidic methods to monitor the phase behaviour of nanoparticles during digestion of lipid-based drug formulations using in situ X-ray scattering’ by Ben J. Boyd et al. , Soft Matter , 2019, 15 , 9565–9578.
Article
The performance of orally administered lipid-based drug formulations is crucially dependent on digestion, and understanding the colloidal structures formed during digestion is necessary for rational formulation design. Previous studies using the established bulk pH-stat approach (Hong et al. 2015), coupled to synchrotron small angle X-ray scatterin...
Chapter
Food emulsions are complex formulations developed with many success criteria, including stability, safety, taste, and process feasibility. A key component of all these attributes is the correct choice of one, or multiple, emulsifiers that are compatible with all ingredients, food regulations, and the above criteria. The physical chemistry of emulsi...
Article
Arrested coalescence occurs in Pickering emulsions where colloidal particles adsorbed on the surface of the droplets become crowded and inhibit both relaxation of the droplet shape and further coalescence. The resulting droplets have a nonuniform distribution of curvature and, depending on the initial coverage, may incorporate a region with negativ...
Article
Full-text available
Microcapsules with controlled stability and permeability are in high demand for applications in separation and encapsulation. We have developed a bio-interfacial process to fabricate strong, but flexible, porous microcapsules from bacterial cellulose at an oil-water emulsion interface. A broad range of microcapsule sizes has been successfully produ...
Article
Cubic and hexagonal liquid crystalline particles, or cubosomes and hexosomes, are used as templates to polymerize various monomers to produce particles with unique micron-scale geometric shapes. Emulsion droplets containing water, ethanol, and the lipid glyceryl monooleate are suspended in a yield stress fluid and used to produce shapes based on cu...
Article
Polyelectrolyte microgels find many uses as rheological modifiers and stimulus-responsive materials. Understanding their swelling and collapse dynamics therefore holds broad importance in science and technology. We report remarkably simple experiments, requiring little sophistication, that reveal the subtle physics of microgel collapse. Millimeter-...
Article
Full-text available
Microstructural effects on suspension and yielding are studied in aqueous dispersions of bacterial cellulose fibers using a small suspended air bubble as a sensitive probe particle. An external pressure field is used to control the applied stress and characterize very early stages of fluid yielding, as well as more developed flow. The bubble allows...
Article
Full-text available
Complex fluids are widely used in formulated products to impart rheological properties like stability, performance, and aesthetics. Yield stress fluids are a particularly important example, enabling applications like particle suspension, surface coating, and therapeutic delivery. Recent work has shown that particle suspension in yield stress fluids...
Preprint
Full-text available
An important strategy to stabilize emulsions is to arrest coalescence of the constituent droplets with an opposing rheological force. Colloidal particles adsorbed on the surface of emulsion droplets in a Pickering emulsion become increasingly crowded during successive coalescence events because the combined surface area of coalescing droplets is le...
Article
Soft, rotationally symmetric particles of dispersed hexagonal liquid crystalline phase are produced using a method previously developed for cubosome microparticle production. The technique forms hexosome particles via removal of ethanol from emulsion droplets containing monoolein, water, and one of the various hydrophobic molecules: vitamin E, hexa...
Article
The stable configurations formed by two poroelastic, ellipsoid-shaped droplets during their arrested coalescence has been investigated using micromanipulation experiments. Ellipsoidal droplets are produced by millifluidic emulsification of petrolatum into a yield stress fluid that preserves their elongated shape. The liquid meniscus between droplet...
Article
The interfacial structures of a range of amphiphilic molecules are studied with both 'soft' and 'hard' hydrophobic substrates. Neutron reflection and quartz crystal microbalance with dissipation (QCM-D) measurements highlight the differences between the adsorbed structures adopted by sodium dodecyl sulfate (SDS), cetyltrimethylammonium bromide (C16...
Preprint
Full-text available
The stable configurations formed by two viscoelastic, ellipsoid-shaped droplets during their arrested coalescence has been investigated using micromanipulation experiments. Ellipsoidal droplets are produced by millifluidic emulsification of petrolatum into a yield stress fluid that preserves their elongated shape. The liquid meniscus between drople...
Article
Through several complementary experiments, an investigation of the bulk and interfacial flows that emerged during the coalescence of two water-in-oil droplets with asymmetric compositional properties was performed. By adding surfactant to one of the coalescing droplets and leaving the other surfactant-free, a strong interfacial tension gradient (i....
Article
Atmospheric air plasma has previously been shown to be a novel and effective method for biofilm eradication. Here we study the effects of plasma on both microbial inactivation and induced structural modification for forming biofilms. New structures are created from aggregates of extracellular polysaccharides and dead bacterial cells, forming a prot...
Article
Oil-in-water emulsion droplets, containing an elastic endoskeleton that holds the droplets in various non-spherical shapes, are formed by crystallizing a portion of the oil phase into a network of wax crystals. Such structures have recently been found to provide enhanced active ingredient delivery and shape-changing responsiveness, but robust metho...
Article
A model of internally-structured emulsion droplets is presented that accounts for the traction forces generated by interfacial tension and the von Mises yield criterion of the internal supporting network. For symmetric droplets, the method calculates the total stress acting on a droplet locally, allowing droplet stability and location of failure to...
Article
Soft polyhedral particles based on variations of the cubic symmetry group are produced from a precursor emulsion by extracting solvent to grow facets on the droplets. The droplets transform into liquid crystals with solid-like rheology and controlled size and shape. Small-angle x-ray scattering confirms a bicontinuous cubic liquid crystalline phase...
Article
Purpose: Thickening polymers have been used as excipients in nasal formulations to avoid nasal run-off (nasal drip) post administration. However, increasing the viscosity of the formulation can have a negative impact on the quality of the aerosols generated. Therefore, the study aims to investigate the use of a novel smart nano-cellulose excipient...
Article
The stability of shapes formed by three viscoelastic droplets during their arrested coalescence has been investigated using micromanipulation experiments. Addition of a third droplet to arrested droplet doublets is shown to be controlled by the balance between interfacial pressures driving coalescence and internal elasticity that resists total cons...
Article
Oil-in-water emulsions stabilized with methylcellulose (MC) varied in stability depending on the composition of the fat phase. When droplets were composed entirely of liquid oil, MC was able to form a continuous, protective film around the droplets. Therefore, when two liquid oil droplets were brought into contact, they underwent extreme shape defo...
Article
Infections arising in hospitalized patients, particularly those who have undergone surgery and are reliant on receiving treatment through biomedical devices, continue to be a rising concern. It is well known that aqueous mixtures of oppositely charged surfactant and polymer molecules can self-assemble to form liquid crystalline structures primarily...
Article
For two approaching oil droplets, a region of arrested coalescence lies between full coalescence and total stability. Here the fusion of two droplets begins, but they are stopped from fully relaxing into one spherical droplet. The internal rigidity of the solid fat network within each droplet can provide the resistance necessary to arrest the shape...
Article
Arrested droplet coalescence produces stable anisotropic shapes and is a key mechanism for microstructure development in foods, petroleum and pharmaceutical formulations. Past work has examined the dynamic elastic arrest of coalescing monodisperse droplet doublets and developed a simple model of doublet strain as a function of physical variables. A...
Presentation
Full-text available
A method to calculate the shear rate (or G-value) that takes account of impeller geometry. The energy dissipation rate in the trailing vortices, which form at the the tip of impeller blades, determines the shear that the flocs experience and their size.
Article
The photoinitiators used in light mediated hydrogelation have been limited due to cytotoxicity and solubility issues. Here we report the use of riboflavin and flavin mononucleotide as nontoxic, naturally occurring photoinitiators for the thiol-ene hydrogelation of functionalised poly(ethylene glycol). High Resolution Magic Angle Spinning (HRMAS) NM...
Article
The self-assembly of ordered structures in mixtures of oppositely charged surfactant and polymer systems has been exploited in various cleaning and pharmaceutical applications and continue to attract much interest since their discovery in the late twentieth century. The ability control the electrostatic and hydrophobic interactions that dictate the...
Article
Full-text available
The synthesis of polymeric nanocapsules in the approximate diameter range 40-100 nm (TEM/SEM) using catanionic surfactant vesicle templates stabilized by subcritical CO2 is demonstrated. Near equimolar aqueous solutions of the surfactants sodium dodecyl sulfate (SDS) and dodecyltrimethylammonium bromide (DTAB) experienced immediate vesicle destabil...
Article
Micron-scale rod-shaped droplets with a range of aspect ratios are produced using extrusion of oil containing a soft wax crystal network to permit shape customization. A physical model of the droplet shape stability is developed based on balancing interfacial stresses with the internal crystal network yield stress. The model predicts the mechanical...
Article
Full-text available
Non-spherical emulsion droplets can be stabilized by densely packed colloidal particles adsorbed at their surface. In order to understand the microstructure of these surface packings, the ordering of hard spheres on ellipsoidal surfaces is determined through large scale computer simulations. Defects in the packing are shown generically to occur mos...
Article
Fat crystals, like other colloidal particles, can influence the stability of food emulsions. Unlike colloidal particles added to form Pickering emulsions, however, crystals form within food emulsion droplets via crystallization and then the crystal wettability determines its ultimate partitioning relative to the oil-water interface. Most descriptio...
Article
The delivery of suspended active ingredients to a surface is a central function of numerous commercial cosmetic, drug, and agricultural formulations. Many products use liquid droplets as a delivery vehicle but, because interfacial tension keeps droplets spherical, these materials cannot exploit the benefits of anisotropic shape and shape change off...
Article
Nanostructured capsules comprised of the anionic bile salt, sodium taurodeoxycholate (STDC) and the biocompatible cationic polymer, chitosan, were prepared to assess their potential as novel tailored release nanomaterials. For comparison, a previously studied system, sodium dodecyl sulphate (SDS) and polydiallyldimethylammonium chloride (polyDADMAC...
Article
Yield stress fluids are widely used in industry, deeply studied as an example of soft matter, and easy to conceptually describe: A solid-like material that can be yielded and made to flow by applying a minimum stress but will re-solidify once the applied stress is removed. Similarly, a particle will be stably suspended against sedimentation by a yi...
Article
Full-text available
There are many new approaches to designing complex anisotropic colloids, often using droplets as templates. However, droplets themselves can be designed to form anisotropic shapes without any external templates. One approach is to arrest binary droplet coalescence at an intermediate stage before a spherical shape is formed. Further shape relaxation...
Article
Droplet breakup of many Newtonian fluids is well described by current experiments, theory, and simulations. Breakup in complex fluids where interactions between mesoscopic structural features can affect the flows remains poorly understood and a burgeoning area of research. Here, we report on our investigations of droplet breakup in thermotropic liq...
Article
Full-text available
When two emulsion drops begin to coalesce, their complete fusion into a single spherical drop can sometimes be arrested in an intermediate shape if a rheological resistance offsets the Laplace pressure driving force. Arrested coalescence of droplets is important, both for its broad impact on commercial food production as well as its potential for f...
Article
The flocculation of polystyrene particles with aluminum sulfate or alum (Al2 (SO4)3) by turbulent shear was studied as a function of the applied shear rates (63–129 s−1) and flocculant concentrations (11 and 32 mg/L) in a stirred tank. Increasing the shear rate increased the floc growth rate but decreased the maximum attainable floc size. Increasin...
Article
We investigate droplet breakup of a thermotropic liquid crystal in the smectic, nematic, and isotropic phases. The experiment consists of varying the ambient temperature to control the liquid crystalline phase and imaging breakup using a fast video camera. We find breakup of the smectic phase is well described by existing theory for a shear thinnin...
Conference Paper
Whether you are manufacturing multi-ingredient suspensions on the industrial scale or designing model biological systems in the laboratory, controlling the scale and uniformity of the sample's rheology is necessary. In order to enable predictive and inferential assessments of a complex fluid's mechanical properties, the underlying structure has to...
Article
We review the diverse range of materials made up of rod-shaped colloids. A common feature of such suspensions is the strong and efficient contribution of rods to the material's solid-like rheological properties such as elastic modulus and yield stress. Colloidal rod suspensions span from biomaterials such as f-actin and fd virus to inorganic materi...
Article
Droplet pinch-off of fluids with liquid crystalline order is a common yet poorly understood process. We report on measurements of pinch-off dynamics for a lyotropic surfactant/water solution in the lamellar phase and a thermotropic liquid crystal in the smectic phase. We find pinch-off is universal and well described by a similarity solution for a...
Conference Paper
Particle sedimentation in complex fluid products is rarely desirable and rheological modification is frequently used to guard against such instabilities. However, a fluid rheology that prevents sedimentation under static conditions may not be useful during transport when a wide range of vibrational frequencies is encountered. This work studies the...
Article
We introduce a model system consisting of self-assembled polyamide anisotropic colloids suspended in an aqueous surfactant solution for studies of the dynamics of rod networks, gels, and glasses. The colloidal particles are formed by recrystallization of a polyamide from an aqueous surfactant phase at temperatures from 59 to 100 degrees C. The aspe...
Article
Droplet pinch-off in air is a common phenomenon that occurs all around us. At the point of pinch-off, the drop radius shrinks to zero in a finite amount of time. The pressure exerted by the interface is inversely proportional to the minimum radius and becomes singular at Pinch-off. In Newtonian fluids, this finite time singularity gives rise to uni...
Article
We introduce a model system consisting of self-assembled polyamide anisotropic colloids suspended in aqueous surfactant solutions. The colloidal particles are formed by precipitation from an amorphous polyamide powder that is dispersed with mechanical agitation in an aqueous surfactant phase at temperatures from 59 to 100^oC. The aspect ratio incre...
Article
Full-text available
The authors describe a rational approach to an important step in video microscopy particle tracking called noise discrimination. Using the morphol. of the brightness profiles produced by the particles, false and dubious detections are eliminated from the valid tracking data. This selection process is found to affect the spatial resoln. .vepsiln. an...
Article
The emulsion templating of ordered colloidal microsphere assemblies by Manoharan et al. involves a consolidation process where dispersed phase fluid is transported from droplets into a continuous phase. Consolidation can be approximated as a diffusion process with moving boundaries. The kinetics of consolidation are investigated here by following d...
Article
Full-text available
Particle tracking microrheology is used to study the effect of a constant applied shear during gelation of aqueous gellan gum with a monovalent salt. Shear modifies the gellan gum hydrogel microstructure and the bulk rheological properties of the system, depending on whether shear is applied during gelation or afterwards. The microstructure determi...
Article
Full-text available
Dense packing of small clusters of microspheres proposed by Manoharan, et al. involves removal of fluid from the droplets (dispersed phase) into the continuous phase, which is referred to as the consolidation process. The consolidation process can be characterized as a diffusion process with moving boundaries. Therefore its dynamics is largely cont...
Article
When a droplet approaches a solid surface, the thin liquid film between the droplet and the surface drains until an instability forms and then ruptures. In this study, we utilize microfluidics to investigate the effects of film thickness on the time to film rupture for water droplets in a flowing continuous phase of silicone oil deposited on solid...
Article
Liquid oil emulsion droplets can violently dewet their own solid crystals during crystallization as a result of surfactant adsorption. The crystal shape formed is a function of the relative rates of dewetting and crystallization as controlled by surfactant adsorption, cooling rate, and lipid purity. For negligible dewetting rates, crystals nucleate...
Article
Dispersed particles of bicontinuous cubic liquid crystalline phase, cubosomes, are self-assembled nanostructured particles that can be formed in aqueous lipid and surfactant systems. Contributions to cubosome research have come from the fields of biology, material science, medicine, and mathematics and much is known about their formation and proper...
Article
Cubosomes are nanoparticles but instead of the solid particles usually encountered, cubosomes are self-assembled liquid crystalline particles with a solid-like rheology that provides unique properties of practical interest. The discovery of cubosomes is a unique story and spans the fields of food science, differential geometry, biological membranes...
Conference Paper
Processing complex fluid products on the industrial scale requires knowledge linking microstructure and rheology to product stability against phase separation. Although homogeneous complex fluids offer many challenges to reproducible processing, fluids with shear-dependent heterogeneous microstructures are especially complicated. Particle tracking...
Conference Paper
Liquid oil emulsion droplets can violently dewet their own solid crystals during crystallization as a result of surfactant adsorption. The crystal shape formed is a function of the relative rates of dewetting and crystallization as controlled by surfactant adsorption, cooling rate, and lipid purity. For negligible dewetting rates, crystals nucleate...
Article
Optical microscopy is used to study the mechanism of cubosome formation via dilution of ethanol solutions of the monoglyceride monoolein. When water is used for dilution, large cubosomes form that require further dispersion. When aqueous Poloxamer 407 solution is used for dilution, spontaneous emulsification occurs, forming numerous sub- micron par...
Article
Over the past few years, bicontinuous cubic phase liquid crystals have been investigated for their applicability to controlled delivery of active ingredients. These liquid crystals have a unique structure of interpenetrating channels of water and lipid that provides compatibility with water-soluble, lipid-soluble, and amphiphilic active ingredients...
Conference Paper
Optical microscopy is used to study the mechanism of cubosome formation via dilution of ethanol solutions of the monoglyceride monoolein. When water is used for dilution, large cubosomes form that require further dispersion. When aqueous Poloxamer 407 solution is used for dilution, spontaneous emulsification occurs, forming numerous sub-micron part...
Article
Cubosomes are dispersed nanostructured particles of cubic phase liquid crystal that have stimulated significant research interest because of their potential for application in controlled-release and drug delivery. Despite the interest, cubosomes can be difficult to fabricate and stabilize with current methods. Most of the current work is limited to...
Article
Titania particle formation by TiCl4 gas phase oxidation, surface growth and coagulation is investigated by a moving sectional population balance model. The dynamic evolution of the detailed particle size distribution is studied accounting for and neglecting the effect of surface growth. The effects of process temperature, T, and precursor volume fr...
Article
A novel process for producing cubic liquid crystalline nanoparticles (cubosomes) has been developed. The process entails simple mixing of two waterlike solutions with a minimal input of energy. The key to this process is the inclusion of hydrotrope. Most lipids, such as monoolein, used to form cubic liquid crystals are essentially insoluble in wate...