Switchable Adhesion of Hydrogels to Plant and Animal Tissues.

The ability to "switch on" adhesion between a thin hydrogel and a biological tissue can be useful in biomedical applications such as surgery. One way to accomplish this is with an electric field, a phenomenon termed electroadhesion (EA). Here, it is shown that cationic gels can be adhered by EA to tissues across all of biology.

Complexity in a Simple Self-Assembling System: Lecithin-Water-Ethanol Mixtures Exhibit a Re-Entrant Phase Transition and a Vesicle-Micelle Transition (VMT) on Heating.

We report surprising results for the self-assembly of lecithin (a common phospholipid) in water-ethanol mixtures. Lecithin forms vesicles (∼100 nm diameter) in water. These vesicles are transformed into small micelles (∼5 nm diameter) by a variety of destabilizing agents such as single-tailed surfactants and alcohols.

Reversibly Sticking Metals and Graphite to Hydrogels and Tissues.

We have discovered that hard, electrical conductors (e.g., metals or graphite) can be adhered to soft, aqueous materials (e.

A Smart Skin for Hydrogels That Enables Switchable Solute Release.

Many applications of hydrogels rely on their ability to deliver encapsulated solutes, such as drugs; however, small hydrophilic solutes rapidly leak out of gels by diffusion. A need exists for a way to regulate solute release out of gels─to ensure zero release until a desired time (the OFF state) and thereafter for the release to be switched ON at a high rate. This should ideally be a repeatable switch; i.

Chemically Fueled Dissipative Cross-Linking of Protein Hydrogels Mediated by Protein Unfolding.

Cells assemble dynamic protein-based nanostructures far from equilibrium, such as microtubules, in a process referred to as dissipative assembly. Synthetic analogues have utilized chemical fuels and reaction networks to form transient hydrogels and molecular assemblies from small molecule or synthetic polymer building blocks. Here, we demonstrate dissipative cross-linking of transient protein hydrogels using a redox cycle, which exhibit protein unfolding-dependent lifetimes and mechanical properties.

Spontaneous Formation of Stable Vesicles and Vesicle Gels in Polar Organic Solvents.

The self-assembly of lipids into nanoscale vesicles (liposomes) is routinely accomplished in water. However, reports of similar vesicles in polar organic solvents like glycerol, formamide, and ethylene glycol (EG) are scarce. Here, we demonstrate the formation of nanoscale vesicles in glycerol, formamide, and EG using the common phospholipid lecithin (derived from soy).

Tensile Testing of Aged Flexible Unidirectional Composite Laminates for Body Armor.

Flexible Unidirectional (UD) composite laminates are commonly being used for ballistic-resistant body armor. These laminates comprise UD layers, each constructed by laminating thin layers of high-performance fibers held in place using very low modulus binder resins, with the fibers in each layer oriented parallel to each other. As these materials are used in body armor, it is important to investigate their long-term reliability, particularly with regards to exposure to temperature and humidity as these are known causes of degradation in other commonly used body armor materials.

Cutting Procedures, Tensile Testing, and Ageing of Flexible Unidirectional Composite Laminates.

Many body armor designs incorporate unidirectional (UD) laminates. UD laminates are constructed of thin (<0.05 mm) layers of high-performance yarns, where the yarns in each layer are oriented parallel to each other and held in place using binder resins and thin polymer films.

Multiscale Polymer Dynamics in Hierarchical Carbon Nanotube Grafted Glass Fiber Reinforced Composites.

Carbon nanotube (CNT) grafted glass fiber reinforced epoxy nanocomposites (GFRP) present a range of stiffnesses (MPa to GPa) and length scales (m to nm) at the fiber-matrix interface. The contribution of functionalized CNT networks to the local and bulk polymer dynamics is studied here by using a combination of torsion dynamical mechanical thermal analysis (DMTA), positron annihilation lifetime spectroscopy (PALS), and neutron scattering (NS) measurements. DMTA measurements highlight a reduction in the storage modulus (') in the rubbery region and an asymmetric broadening of the loss modulus (″) peak in the -transition region.