Nancy R. Sottos

• University of Illinois Urbana-Champaign

Frontal polymerization (FP) has emerged as a rapid and energy-efficient process for fabricating thermoset polymers and composites. In this process, a self-propagating reaction front cures the polymer rapidly by the exothermic heat of polymerization reaction instead of an external heat source. Design for FP-based manufacturing in commercial applicat...

The representative volume element (RVE) in fiber composites refers to the smallest volume of material that contains all constituents of the composite, i.e., fiber and matrix, and is a domain in which the homogenization of microscale response will lead to the macroscale behavior. Therefore, the RVE size in fiber composites is the length scale at whi...

Frontal polymerization (FP) is an out-of-autoclave, self-sustaining cure process that enables rapid and energy-efficient manufacturing of composites compared to conventional processes. Prior FP demonstrations for both polymer and composite materials rely on one polymerization front to achieve full cure. In this work, we investigate the effect of mu...

We formulate a homogenized thermo-chemical model to simulate the manufacturing of unidirectional composites made of carbon fibers embedded in a thermosetting dicyclopentadiene (DCPD) matrix using frontal polymerization (FP). The reaction-diffusion model is then solved using the finite element method to investigate the evolution of the temperature a...

Electrodes experience significant mechanical degradation at fast charging/discharging rates, ultimately leading to particle fracture and capacity loss. In this work, we investigate the role of an Au surface coating on the intercalation-induced strain changes in lithium manganese oxide (LiMn2O4, LMO) composite cathode electrodes. In-situ strain meas...

Digital image correlation of scanning electron microscope images is a powerful technique for measuring full-field deformation at microstructural length scales. A major challenge in applying this technique is the fabrication of speckle patterns small enough to facilitate full-field measurements with high spatial resolutions and at high magnification...

Volumetric changes due to repeated lithiation and delithiation are a significant source of electrode degradation and capacity fade in rechargeable batteries. Measurement of such volumetric changes and their resultant electro-chemo-mechanical strains and stresses have previously been investigated in conventional liquid-electrolyte Li-ion batteries....

Thermoset polymers are commonly used as the matrix material in fiber-reinforced polymer composites (FRPCs) due to their good mechanical properties, chemical stabilities, and ease of manufacturing. Conventional curing of thermosets and their composites requires heating the matrix monomers at elevated temperatures during long cure cycles for producin...

Detection and assessment of small-scale damage at early stages are essential for polymeric materials to extend lifetime, avoid catastrophic structural failure, and improve cost-efficiency. Previous self-reporting coatings provide visual indication of surface damage but have been limited to a single layer without information on the depth of crack pe...

We investigate the effect of pulling point location on the mechanochemical activation of two isomers of spiropyran in cross-linked polymeric materials through computational calculations and in situ fluorescence measurements. The threshold stress and strain required to activate the spiropyran mechanophores under tensile load are characterized. For b...

The corrosion of steel substrates causes damage that is costly to repair or replace. Current protective coatings predominately rely on environmentally harmful anticorrosive agents and toxic solvents to protect the underlying substrate. The use of lawsone (2-hydroxy-1,4-napthoquinone) together with a water-based epoxy coating provides an environment...

Microvascular self-healing systems have previously been demonstrated to restore large-scale damage and achieve repeated healing of multiple damage events in polymers. However, the healing performance of these systems is often limited because the laminar nature of flow in microchannels results in poor mixing of two-part self-healing reagents. In thi...

Thermoset polymers and composite materials are integral to today's aerospace, automotive, marine and energy industries and will be vital to the next generation of lightweight, energy-efficient structures in these enterprises, owing to their excellent specific stiffness and strength, thermal stability and chemical resistance1-5. The manufacture of h...

A new methodology is developed to activate and characterize mechanochemical transformations at a solid interface. Maleimide-anthracene mechanophores covalently anchored at a fused silica-polymer interface are activated using laser-induced stress waves. Spallation-induced mechanophore activation is observed above a threshold activation stress of 149...

Flame retardant tris(2-chloroethyl phosphate) (TCP) is successfully encapsulated in core–shell poly(urea-formaldehyde) microcapsules by in situ polymerization. The microcapsules are electrochemically stable in lithium-ion (Li-ion) battery electrolytes and thermally stable to ca. 200 °C. Thermal triggering of these microcapsules at higher temperatur...

Lithium manganese oxide, LiMn2O4 (LMO) is a promising cathode material, but is hampered by significant capacity fade due to instability of the electrode-electrolyte interface, manganese dissolution into the electrolyte and subsequent mechanical degradation of the electrode. In this work, electrochemically-induced strains in composite LMO electrodes...

Lithium manganese oxide cathodes used in Li-ion batteries suffer from manganese dissolution and capacity fade. We present a new technique for directly measuring the manganese ion (Mn²⁺) concentration in a typical Li-ion carbonate electrolyte using 4-(2-pyridylazo) resorcinol (PAR) as a UV-vis probe. Chelation between PAR and Mn²⁺ ion induces a char...

A hybrid microcapsule–microvascular system is introduced to regenerate the multiscale damage that results from impact puncture of vascularized polymeric sheets. Microvascular delivery of a two-stage healing agent restores lost damage volume (puncture) to recover impact energy absorption, while embedded microcapsules heal microcracks to facilitate s...

In article number 1704197, Scott R. White and co-workers present a novel hybrid system that incorporates both microcapsules and microvascular delivery for the restoration of impact puncture damage. The image shows the damage with radiating microcracks repaired by ruptured embedded microcapsules (green), and the central puncture being restored with...

Cyclic poly(phthalaldehyde) (cPPA) is a metastable and stimuli responsive polymer that undergoes rapid solid state depolymerization and has been utilized as a packaging and encapsulating material for transient applications. However, the early onset thermal depolymerization of cPPA severely hinders the fabrication and processing of plastic parts. He...

Self-assembled monolayers (SAMs) are aggregates of small molecular chains that form highly ordered assemblies at the nanoscale. They are excellent contenders of molecular-level tailoring of interfaces because of the wide choice of terminal groups. Molecular dynamics (MD) simulations and experimental observations of spallation of two SAM-enhanced go...

Time-release of encapsulated vinylene carbonate (VC) from microcapsules in Li-ion batteries is demonstrated to enhance the rate performance without sacrificing capacity retention. VC-filled microcapsules are successfully prepared by a solvent exchange method that allows VC to diffuse through the microcapsule shell wall at elevated temperature. The...

Unidirectional glass/epoxy prepreg with embedded microcapsules containing a liquid healing agent was developed for the fabrication of laminated self-healing fiber-reinforced polymer matrix composites (PMCs). Microcapsules containing a liquid healing agent were distributed throughout a prepreg fabric using a custom designed prepregger. The microcaps...

The integration of microchannels within structural composites enables a range of multifunctional responses such as thermal management and self-healing. In this work, we investigate how microchannels affect the crashworthiness of the host material. Corrugated panels are fabricated with aligned microchannels (ca. 400 µm diameter) at different channel...

Post-impact mechanical response of 2D and 3D woven glass/epoxy composite plates and beams of equivalent areal density are evaluated using both Compression-After-Impact (CAI) and Flexure-After-Impact (FAI) testing protocols. Residual strength and stiffness for CAI and FAI are compared after normalization of impact energy with respect to specimen vol...

Low velocity impact damage of 2D and 3D woven glass/epoxy composites with the same areal density and material constituents were examined. Characterization of damage for both plate and beam sample geometries was investigated through the collection of high-resolution cross-sectional images after impact. Load and displacement data collected during imp...

Recurrent self-healing of fracture damage in fiber-reinforced composites was accomplished by incorporating internal vascular networks for repeated delivery of reactive liquid components to an internal delamination. Double cantilever beam specimens containing embedded microvascular channels were repeatedly fractured and healed by pumping individuall...

Self-healing polymers are capable of self-repair either in response to the damage or through external stimuli, but are limited in their ability to autonomously control the volume of healing agents released, in the length scale of damage they address, and in their ability to respond to multiple damage events. Here, the authors report a novel design...

We report a microencapsulation procedure based on rapid solvent evaporation to prepare microcapsules with hydrophobic core materials and low ceiling temperature polymer shell wall of cyclic poly(phthalaldehyde) (cPPA). We use and compare microfluidic and bulk emulsions. In both methods, rapid solvent evaporation following emulsification resulted in...

Frontal ring-opening metathesis polymerization (FROMP) has potential for use in rapid fabrication of structural polymers. However, the high activity of the ruthenium catalyst used for FROMP has limited the working time to <1 h. We report the use of alkyl phosphites as inhibitors for Grubbs’ type catalysts to substantially extend working time. Subtl...

Protective coatings safeguard the underlying substrate material from environmental attack and are critical for operating in harsh conditions. Self-healing materials have been developed for the autonomous repair of damage in coatings. This work demonstrates a regenerative coating system that is a simplified synthetic analog of skin. A protective UV...

Silicon (Si) composite electrodes are developed with increased cycle lifetimes and reliability through dynamic ionic bonding between active Si nanoparticles and a polymer binder. Amine groups are covalently attached to Si nanoparticles via surface functionalization. Si composite electrodes are fabricated by combining the Si nanoparticles with a pol...

A promising pathway for multifunctionality in fiber-composites is to mimic biological vasculature that enables living organisms with concerted homeostatic functions. In this paper, newfound material and processing advancements in vaporization of sacrificial components (VaSC), a technique for creating inverse replica architectures via thermal depoly...

The lifetime of man-made materials is controlled largely by the wear and tear of everyday use, environmental stress and unexpected damage, which ultimately lead to failure and disposal. Smart materials that mimic the ability of living systems to autonomously protect, report, heal and even regenerate in response to damage could increase the lifetime...

In situ strain and stress measurements are performed on composite electrodes to monitor potential-dependent stiffness changes in lithium manganese oxide (LiMn2O4). Lithium insertion and removal results in asynchronous strain and stress generation in the electrode. Electrochemical stiffness changes are calculated by combining coordinated stress and...

Mechanical force alters the potential energy surface of a mechanophore reaction by modifying the activation energy for conversion. The effects of force on the rate constants and activation energies are not well characterized for mechanophores in bulk polymers. In this work, spiropyran-linked polyurethanes are synthesized and the kinetics of the spi...

Electrospun fibers are a promising method for encapsulation of reactive agents in self-healing coatings. Healing is initiated by mechanical damage to the coating causing the fibers to rupture and release their core materials into the damage region. Prior work has demonstrated autonomous healing in coatings containing electrospun fibers, but full ch...

We report the single crystal structure and thermal properties of 1,2-bis(phenylethynyl)benzene (PEB), revealing that PEB forms a metastable liquid at rt, ca. 35 ˚C below its melting point. Accelerated nucleation of PEB from its supercooled state was induced with high reproducibility by a shock wave with ca. 15 ns duration and 1.2 GPa peak pressure....

Transformation of naphthopyran into a colored merocyanine species in polymeric materials is achieved using mechanical force. We demonstrate that the mechanochemical reactivity of naphthopyran is critically dependent on the regiochemistry, with only one particular substitution pattern leading to successful mechanochemical activation. Two alternative...

Microscopic damage inevitably leads to failure in polymers and composite materials, but it is difficult to detect without the aid of specialized equipment. The ability to enhance the detection of small-scale damage prior to catastrophic material failure is important for improving the safety and reliability of critical engineering components, while...

Although lithium-ion batteries are ubiquitous in portable electronics, increased charge rate and discharge power are required for more demanding applications such as electric vehicles. The high-rate exchange of lithium ions required for more power and faster charging generates significant stresses and strains in the electrodes that ultimately lead...

Repeated charge and discharge of graphite composite electrodes in lithium-ion batteries cause cyclic volumetric changes in the electrodes, which lead to electrode degradation and capacity fade. In this work, we measure in situ the electrochemically-induced deformation of graphite composite electrodes. The deformation is divided into a reversible co...

The energy absorption response of polyurea thin films is investigated under laser-induced dynamic mixed-mode loading. By exploiting the substrate geometry, the arrival times and the convenience of two simultaneously detected waves (longitudinal and shear), the transient shear loading of thin films is achieved under mixed-mode conditions. Polyurea f...

Poly(urea-urethane) thermosets containing the 1-tert-butylethylurea (TBEU) structure feature a reversible dissociation/association process of their covalent linkages under mild conditions. Unlike conventional thermosets, TBEU-based poly(urea-urethane) thermosets maintain their malleability after curing. Under high temperature (100 °C) and applied p...

An automatic crack tracking scheme is developed for measuring the tensile opening (mode I) interlaminar fracture toughness (GIc) of continuous glass fiber-reinforced composite materials. The technique is directly compared to ASTM standard D5528, which contains a manual procedure to obtain GIc values from crack length data using a double cantilever...

A 3D NURBS-based interface-enriched generalized finite element method (NIGFEM) is introduced to solve problems with complex discontinuous gradient fields observed in the analysis of heterogeneous materials. The method utilizes simple structured meshes of hexahedral elements that do not necessarily conform to the material interfaces in heterogeneous...

The maximum volume that can be restored after catastrophic damage in a newly developed regenerative polymer system is explored for various mixing, surface wetting, specimen configuration, and microvascular delivery conditions. A two-stage healing agent is implemented to overcome limitations imposed by surface tension and gravity on liquid retention...

Functional groups in self-assembled monolayers (SAMs) provide a way to tailor the structural, thermal and electrical properties of interfaces, as the interaction between SAMs and target surfaces can range from weakly bonded to strong bonding. The present study focuses on evaluating the interfacial mechanical properties of SAMs with different affini...

Smart polymeric materials that autonomously indicate mechanically damaged areas are developed by N. R. Sottos and co-workers, as described on page 2189. Microcapsules containing the color-changing indicator are homogeneously dispersed in a polymer matrix. Mechanical damage (e.g., scratch, abrasion, or compression) causes the microcapsules to ruptur...

Microvascular shape memory alloy (SMA)-polymer matrix composite (PMC) hybrid materials are fabricated using the Vaporization of Sacrificial Components (VaSC) technique. Two types of sacrificial materials are used: Mg wires in the SMA (nickel titanium) and poly(lactic acid)/tin(II) oxalate fibers in the PMC (glass fiber/epoxy). These sacrificial mat...

High resolution in situ autonomous visual indication of mechanical damage is achieved through a microcapsule-based polymeric material system. Upon mechanical damage, ruptured microcapsules release a liquid indicator molecule. A sharp color change from light yellow to bright red is triggered when the liberated indicator 2′,7′-dichlorofluorescein rea...

Understanding shockwave-induced physical and chemical changes of impact-absorbing materials is an important step toward the rational design of materials that mitigate the damage. In this work, we report a series of network-forming ionic liquids (NILs) that possess an intriguing shockwave absorption property upon laser-induced shockwave. Micro-struc...

Exposure to high heat can cause polymer matrix composites (PMC) to fail under mechanical loads easily sustained at room temperature. However, heat is removed and temperature reduced in PMCs by active cooling through an internal vascular network. Here we compare structural survival of PMCs under thermomechanical loading with and without active cooli...

Self-healing is a natural process common to all living organisms which provides increased longevity and the ability to adapt to changes in the environment. Inspired by this fitness-enhancing functionality, which was tuned by billions of years of evolution, scientists and engineers have been incorporating self-healing capabilities into synthetic mat...

Selbstheilung ist ein natürlicher Vorgang, der allen lebenden Organismen zu eigen ist und eine höhere Lebensspanne sowie die Fähigkeit zur Anpassung an Umgebungsveränderungen mit sich bringt. Inspiriert von dieser evolutionär entwickelten Funktionalität haben Wissenschaftler und Ingenieure synthetische Materialien mit Selbstheilungsvermögen erschaf...

Thermally triggered degradation of transient electronics is accomplished by S.R. White and co-workers using protective wax coatings that melt and release encapsulated acid microdroplets, as described on page 3783. A self-destructive device is shown, where heat triggering is remotely controlled. The heater of the device is wirelessly powered through...

A thermoplastic resin poly(bisphenol A-co-epichlorohydrin) (PBAE) is blended with a high glass transition temperature (Tg) epoxy matrix to serve as both a toughening additive and a healing agent in combination with an encapsulated solvent. Microcapsules are coated with poly(dopamine) (PDA) to improve the thermal stability and retain the core solven...

An actively cooled vascular polymer matrix composite containing 3.0% channel volume fraction retains greater than 90% flexural stiffness when exposed continuously to 325 °C environmental temperature. Non-cooled controls suffered complete structural failure through thermal degradation under the same conditions. Glass–epoxy composites (Tg = 152 °C) m...

For the first time, repeatable self-healing was achieved in a cross-linked epoxy polymer by incorporating 2-ethyl-4-methylimidazole (24-EMI) into the matrix as a latent polymerization initiator. Upon material damage and infiltration of liquid EPON 8132 epoxy monomer healing agent into the crack plane, polymerization occurs in the damaged region wit...

Thermally triggered transient electronics using wax-encapsulated acid, which enables rapid device destruction via acidic degradation of the metal electronic components is reported. Using a cyclic poly(phthalaldehyde) (cPPA) substrate affords a more rapid destruction of the device due to acidic depolymerization of cPPA. © 2015 WILEY-VCH Verlag GmbH...

An automatic crack tracking scheme is developed for measuring the tensile opening (mode I) interlaminar fracture toughness (GIc) of continuous glass fiber-reinforced composite materials. The technique is directly compared to ASTM standard D5528, which contains a manual procedure to obtain G Ic values from crack length data using a double cantilever...

A protective polydopamine (PDA) coating is applied to core-shell microcapsule surfaces by the polymerization of dopamine monomers. A neutral aqueous solution and the addition of an oxidant (i.e. ammonium persulfate) are crucial for microcapsule survival and the initiation of PDA polymerization, respectively. The resulting PDA coating is a dense and...

Fully autonomous, room temperature self-healing in PMMA is achieved for the first time through the use of microcapsules containing a solvent. Linear PMMA is embedded with microcapsules (ca. 300 μm) containing a liquid anisole solvent core and a small amount of linear PMMA polymer for healing of crack damage. Specimens containing a range of concentr...

A non-uniform rational B-splines (NURBS)-based interface-enriched generalized finite element method is introduced to solve problems with complex discontinuous gradient fields observed in the structural and thermal analysis of the heterogeneous materials. The presented method utilizes generalized degrees of freedom and enrichment functions based on...

Introduction NIGFEM: Formulation and Implementation Results and Discussion Conclusions Acknowledgements

S. R. White and co-workers develop sacrificial templates of 0D to 3D used to create vascular and porous architectures in polymers on page 1043. Embedded sacrificial templates are removed using a thermal treatment process, VaSC, leaving behind an inverse replica. This reconstruction of microCT imaging shows 3D channel architecture created using a 3D...

Inspired by damage repair in biological systems, S. R. White and team demonstrate a novel self-healing system in a non-living commercial biomaterial on page 202. This self-healing acrylic bone cement is enabled by solvent-filled microcapsules, which heal crack damage and restore up to 80% of the initial fracture toughness of the cement. This innova...

A 3D NURBS-based interface-enriched generalized FEM (NIGFEM) is developed to analyze problems with complex, discontinuous gradient fields commonly observed in the structural analysis of heterogeneous materials, with emphasis on polymer matrix composites. In the proposed approach, the mesh generation process is significantly simplified by utilizing...

Experimental and Applied Mechanics, Volume 6: Proceedings of the 2014 Annual Conference on Experimental and Applied Mechanics, the sixth volume of eight from the Conference, brings together contributions to important areas of research and engineering. The collection presents early findings and case studies on a wide range of topics, including: Adva...

A method of making a composite material provides a composite material that includes a polymeric layer and a substrate, in contact with the polymeric layer, where the substrate includes a substrate matrix, a first microfluidic network in the substrate matrix and in fluid communication with the polymeric layer, and a polymerizer in the first microflu...

The conductive polymer precursor, 3-hexylthiophene (3-HT), is successfully encapsulated in ca. 5 μm polyamide microcapsules by interfacial polymerization. The microcapsules are thermally stable up to 300°C, and electrochemically stable in a Li-ion battery electrolyte. Mechanical rupture of the microcapsules releases the liquid core and electropolym...

Triggerable transient electronics are demonstrated with the use of a metastable poly(phthalaldehyde) polymer substrate and encapsulant. The rate of degradation is controlled by the concentration of the photo-acid generator and UV irradiance. This work expands on the materials that can be used for transient electronics by demonstrating transience in...

Complex multidimensional vascular polymers are created, enabled by sacrificial template materials of 0D to 3D. Sacrificial material consisting of the commodity biopolymer poly(lactic acid) is treated with a tin catalyst to accelerate thermal depolymerization, and formed into sacrificial templates across multiple dimensions and spanning several orde...

A self-indicating material system may include a solid polymer matrix having a first color, a first plurality of capsules in the matrix, and a plurality of particles in the matrix. The first plurality of capsules includes a first reactant, and the plurality of particles includes a second reactant, which forms a product when in contact with the first...

Self-assembled monolayers (SAMs) provide an enabling platform for molecular tailoring of the chemical and physical properties of an interface. In this work, we systematically vary SAM end-group functionality and quantify the corresponding effect on interfacial failure between a transfer printed gold (Au) film and a fused silica substrate. SAMs with...

Fracture-induced mechanochemical activation is achieved for the first time in a structural engineering polymer. Rubber toughened PMMA is lightly cross-linked (1.0 mol%) with the mechanophore spiropyran by free radical polymerization. Single Edge Notch Tension tests are performed on the spiropyran-linked material and a distinct change in color and f...

Self-healing in orthopedic bone cement is demonstrated with a novel thermoplastic solvent-bonding approach. Low toxicity solvent-filled microcapsules, embedded in a commercial acrylic bone cement matrix, enable recovery of up to 80% of the virgin fracture toughness of the cement at room and body temperature conditions without external stimuli or hu...

By incorporating 3D microvascular networks containing a two-part reactive chemistry within a fiber-reinforced composite, continuous cycles of self-healing after interlaminar delamination are achieved. An interpenetrating vasculature shows improved in situ fluid mixing over segregated microchannels, resulting in full recovery (>100%) of mode-I fract...

The cyclic stress in lithium-ion battery electrodes induced by repeated charge and discharge cycles causes electrode degradation and fracture, resulting in reduced battery performance and lifetime. To investigate electrode mechanics as a function of electrochemical cycling, we utilize digital image correlation (DIC) to measure the strains that deve...

Self-assembled monolayers (SAMs) provide an enabling platform for molecular tailoring of the chemical and physical properties of an interface in an on-demand fashion. In this work, we systematically vary SAM end-group functionality and investigate the failed interface between a transfer printed gold (Au) film and a SAM-functionalized fused silica s...

The regenerative power of tissues and organs in biology has no analog in synthetic materials. Although self-healing of microscopic defects has been demonstrated, the regrowth of material lost through catastrophic damage requires a regenerative-like approach. We demonstrate a vascular synthetic system that restores mechanical performance in response...

Robust microcapsules are prepared with carbon black suspensions high in solids loading (up to 0.2 g/mL) for electrical conductivity restoration. Oxidized carbon black is rendered more hydrophobic through surface functionalization with octadecylamine by two different methods. Functionalization significantly improves dispersability and suspension sta...

Force-induced covalent bond changes in mechanophore-linked polymers typically require large, irreversible material deformation, limiting successive activation cycles. Now, repeated force-induced reactions have been achieved by incorporating flex-activated mechanophores into elastomeric networks.

Vascularization enables multifunctional composites capable of self-healing, thermal regulation, electrical and magnetic modulation, and damage sensing. In this study, the effect of vascular channels on the in-plane tensile properties and damage progression of three-dimensional orthogonally woven textile composites is examined. Vascular channels are...

This work proposes a novel fluidic switch topology on coplanar waveguide transmission lines for high power applications. The bridge is created from a transverse fluidic network over the coplanar waveguide containing dispersions of spherical and high aspect ratio nanoparticles. In particular, the volume fraction of gold or silver nanoparticles dispe...

Thin films of mechanochemically active polymer were subjected to laser-generated, high amplitude acoustic pulses. Stress wave propagation through the film produced large amplitude stresses (>100 MPa) in short time frames (10-20 nanoseconds), leading to very high strain-rates (ca. 10(7)-10(8) s(-1)). The polymer system, spiropyran (SP)- linked polys...

A maximum of 91% recovery of interfacial shear strength (IFSS) is achieved for carbon fiber/epoxy interfaces functionalized with capsules containing reactive epoxy and ethyl phenyl acetate (EPA). We find a binder is necessary to improve the retention of capsules on the carbon fiber surface. Two different methods for applying the binder to the carbo...

Simultaneous measurements of mechanical response, optical birefringence, and fluorescence signal are acquired in situ during tensile testing of a mechanophore-linked elastomeric polymer. Mechanical stress, deformation, and polymer chain alignment are correlated with force-induced chemical reaction of the mechanophore. The mechanochemically responsi...

Abstract Microcapsules containing a liquid metal alloy core of gallium-indium (Ga-In) are prepared via in situ urea-formaldehyde (UF) microencapsulation. The capsule size, shape, thermal properties, and shell wall thickness are investigated. We prepare ellipsoidal capsules with major and minor diameter aspect ratios ranging from 1.64 to 1.08 and wi...

Mechanically induced chemical reactivity is a promising means for designing self-sensing and autonomous materials. Force sensitive chemical groups called mechanophores can be covalently linked into polymers in order to trigger specific chemical reactions upon mechanical loading. A model framework is developed to describe the response of these mecha...