Showing papers by "Emmanuel P. Giannelis published in 2020"

Autonomic perspiration in 3D-printed hydrogel actuators

Abstract: In both biological and engineered systems, functioning at peak power output for prolonged periods of time requires thermoregulation. Here, we report a soft hydrogel-based actuator that can maintain stable body temperatures via autonomic perspiration. Using multimaterial stereolithography, we three-dimensionally print finger-like fluidic elastomer actuators having a poly-N-isopropylacrylamide (PNIPAm) body capped with a microporous (~200 micrometers) polyacrylamide (PAAm) dorsal layer. The chemomechanical response of these hydrogel materials is such that, at low temperatures ( 30°C), the pores dilate to enable localized perspiration in the hydraulic actuator. Such sweating actuators exhibit a 600% enhancement in cooling rate (i.e., 39.1°C minute-1) over similar non-sweating devices. Combining multiple finger actuators into a single device yields soft robotic grippers capable of both mechanically and thermally manipulating various heated objects. The measured thermoregulatory performance of these sweating actuators (~107 watts kilogram-1) greatly exceeds the evaporative cooling capacity found in the best animal systems (~35 watts kilogram-1) at the cost of a temporary decrease in actuation efficiency.

3D printable tough silicone double networks.

Abstract: Additive manufacturing permits innovative soft device architectures with micron resolution. The processing requirements, however, restrict the available materials, and joining chemically dissimilar components remains a challenge. Here we report silicone double networks (SilDNs) that participate in orthogonal crosslinking mechanisms—photocurable thiol-ene reactions and condensation reactions—to exercise independent control over both the shape forming process (3D printing) and final mechanical properties. SilDNs simultaneously possess low elastic modulus (E100% < 700kPa) as well as large ultimate strains (dL/L0 up to ~ 400 %), toughnesses (U ~ 1.4 MJ·m−3), and strengths (σ ~ 1 MPa). Importantly, the latent condensation reaction permits cohesive bonding of printed objects to dissimilar substrates with modulus gradients that span more than seven orders of magnitude. We demonstrate soft devices relevant to a broad range of disciplines: models that simulate the geometries and mechanical properties of soft tissue systems and multimaterial assemblies for next generation wearable devices and robotics. Additive manufacturing processing requirements pose restrictions on materials and joining chemically dissimilar components. Here the authors use silicone double networks that participate in orthogonal crosslinking mechanisms for independent control of the shape forming process and final mechanical properties.

3D Printing of Viscoelastic Suspensions via Digital Light Synthesis for Tough Nanoparticle-Elastomer Composites.

Abstract: The rheological parameters required to print viscoelastic nanoparticle suspensions toward tough elastomers via Digital Light Synthesis (DLS) (an inverted projection stereolithography system) are reported. With a model material of functionalized silica nanoparticles suspended in a poly(dimethylsiloxane) matrix, the rheological-parameters-guided DLS can print structures seven times tougher than those formed from the neat polymers. The large yield stress and high viscosity associated with these high concentration nanoparticle suspensions, however, may prevent pressure-driven flow, a mechanism essential to stereolithography-based printing. Thus, to better predict and evaluate the printability of high concentration nanoparticle suspensions, the boundary of rheological properties compatible with DLS is defined using a non-dimensional Peclet number (Pe). Based on the proposed analysis of rheological parameters, the border of printability at standard temperature and pressure (STP) is established by resin with a silica nanoparticle mass fraction (ϕsilica ) of 0.15. Above this concentration, nanoparticle suspensions have Pe > 1 and are not printable. Beyond STP, the printability can be further extended to ϕsilica = 0.20 via a heating module with lower shear rate to reduce the Pe < 1. The printed rubber possesses even higher toughness (Γ ≈ 155 kJ m-3 ), which is 40% higher over that of ϕsilica = 0.15.

Slow Release of Surfactant Using Silica Nanosized Capsules

Abstract: Engineering and scaling-up nanocarriers for the controlled release of surfactant are imperative for enhanced oil recovery (EOR). Herein, using silica-based nanosized porous capsules to slowly release surfactant in saline water is reported. The results indicate that the silica shell ensures the stability of the protected surfactants in the cores under harsh conditions. Almost negligible release was noticed in salt-free brine [deionized (DI) water]. In saline brine, the particles slowly released surfactant molecules. Forty-six percent of the total surfactant encapsulated was released after 12 days as quantified by the remaining organic content after mixing with brine. Scanning electron microscopy (SEM) analysis confirms the stability of the surfactant incorporated particles in saline water that contains 56 000 mg/L salts.

Non-porous phosphonated ionic silica nanospheres as nanocarriers for efficient intracellular delivery of doxorubicin

Abstract: A novel nanoscale drug delivery system based on monodispersed non-porous ionic silica nanospheres (NISNs) decorated with phosphonated active sides homogeneously distributed all over their surface, was developed. Doxorubicin (DOX), a well-known antitumor drug, was successfully loaded on the surface of the silica nanoparticles via electrostatic interactions. The final drug vehicle possesses excellent solubility, while enhancing significantly the efficacy of the drug. The administration of DOX-loaded NISNs against two aggressive DOX-resistant human prostate adenocarcinoma cell lines DU145 and PC3 leads to increased medicinal efficacy with extremely low DOX concentrations (0.1 μM) that could significantly reduce DOX side effects. In addition, NISNs was found to be non-toxic. The efficient cellular uptake of NISNs_DOX was confirmed by flow cytometry analysis and visualized by confocal microscopy. The translocation of DOX inside cells drastically changed, when DOX was bound to NISNs nanoparticles. Specifically, DOX loaded to NISNs nanoparticles is preferentially localized in the cytosol and significant efficacy was observed due to slow controlled release of DOX to the nucleus. The results reported in this work strongly support the potential utilization of NISNs derivatives as non-toxic nanocarriers for high loading efficiency and intracellular delivery of therapeutic drugs.

Fluorine-free oil repellent coating, methods of making same, and uses of same

Abstract: Provided are fluorine-free, oleophobic layers including one more or polydimethylsiloxane resin layers. The layers can be disposed on a portion of or all of a surface of a substrate. Also provided are methods of making and using same.

Method for epoxidation to produce alkene oxide

Abstract: A hierarchical catalyst composition comprising a continuous or particulate macroporous scaffold in which is incorporated mesoporous aggregates of magnetic nanoparticles, wherein an enzyme is embedded in mesopores of the mesoporous aggregates of magnetic nanoparticles. Methods for synthesizing the hierarchical catalyst composition are also described. Also described are processes that use the recoverable hierarchical catalyst composition for depolymerizing lignin remediation of water contaminated with aromatic substances, polymerizing monomers by a free-radical mechanism, epoxidation of alkenes, halogenation of phenols, inhibiting growth and function of microorganisms in a solution, and carbon dioxide conversion to methanol. Further described are methods for increasing the space time yield and/or total turnover number of a liquid-phase chemical reaction that includes magnetic particles to facilitate the chemical reaction, the method comprising subjecting the chemical reaction to a plurality of magnetic fields of selected magnetic strength, relative position in the chemical reaction, and relative motion.

Slow Release of Surfactant Utilizing Silica Nanosized Capsules

Abstract: Engineering and scaling-up nanocarriers for the controlled release of surfactant are imperative for enhanced oil recovery (EOR). Herein, the use of silica-based nano-sized porous capsules to slowly release surfactant in saline water is reported. The results indicate that the silica shell ensures the stability of the protected surfactants in the cores under harsh conditions. Almost negligible release was noticed at salt-free brine (DI water). In saline brine, the particles slowly released surfactants molecules. 46% of the total surfactant encapsulated was released after 12 days as quantified by the remaining organic content after mixing with brine. Scanning Electron Microscopy (SEM) analysis confirms the stability of the surfactant incorporated particles in saline water that contains 56000 mg/L of salts.