Increasing ionic conductivity within thermoplastics commercial additives results in a dramatic decrease in fiber diameter from melt electrospinning.

Polyethylene melt conductivity was increased by adding a commercial anti-static agent, which resulted in a 20× decrease in electrospun fiber diameter and formation of a significant fraction of sub-micron diameter fibers. Two polyethylene formulations and varying additive concentrations were utilized to span the parameter space of conductivity and viscosity. The key role of conductivity in determining the jet radius (which sets the upper limit on the fiber size) is discussed in the context of fluid mechanics theory and previous simulations.

Nanoparticle-based photothermal heating to drive chemical reactions within a solid: using inhomogeneous polymer degradation to manipulate mechanical properties and segregate carbonaceous by-products.

Photothermal heating via metal nanoparticles is utilized to degrade polyethylcyanoacrylate (PECA), which undergoes a thermally-driven depolymerization process, resulting in (i) monomer loss from the sample, (ii) repolymerization to form shorter chains (oligomer), and (iii) formation of carbonaceous by-products which are graphene-like and luminescent. These unique PECA properties are used to demonstrate the heterogeneous temperature distribution present during photothermal processing and the results are compared to degradation via conventional methods where a uniform temperature is present. Photothermal heating results in formation of pockets of depolymerized material around each nanoscale heating site.

Photothermally-driven thermo-oxidative degradation of low density polyethylene: heterogeneous heating plus a complex reaction leads to homogeneous chemistry.

Photothermal heating from embedded nanoparticles, a process whereby visible light is converted into heat resulting in a high temperature in each particle's immediate vicinity, was utilized to degrade low density polyethylene (LDPE) via thermo-oxidation. The spatially-varying steady-state photothermal temperature field is a potential mechanism by which ambient light (e.g.

Nanoscale steady-state temperature gradients within polymer nanocomposites undergoing continuous-wave photothermal heating from gold nanorods.

Anisotropically-shaped metal nanoparticles act as nanoscale heaters via excitation of a localized surface plasmon resonance, utilizing a photothermal effect which converts the optical energy into local heat. Steady-state temperatures within a polymer matrix embedded with gold nanorods undergoing photothermal heating using continuous-wave excitation are measured in the immediate spatial vicinity of the nanoparticle (referred to as the local temperature) from observing the rate of physical rotation of the asymmetric nanoparticles within the locally created polymer melt. Average temperatures across the entire (mostly solid) sample (referred to as the global temperature) are simultaneously observed using a fluorescence method from randomly dispersed molecular emitters.

Spatial temperature mapping within polymer nanocomposites undergoing ultrafast photothermal heating via gold nanorods.

Heat emanates from gold nanorods (GNRs) under ultrafast optical excitation of the localized surface plasmon resonance. The steady state nanoscale temperature distribution formed within a polymer matrix embedded with GNRs undergoing pulsed femtosecond photothermal heating is determined experimentally using two independent ensemble optical techniques. Physical rotation of the nanorods reveals the average local temperature of the polymer melt in the immediate spatial volume surrounding each rod while fluorescence of homogeneously-distributed perylene molecules monitors temperature over sample regions at larger distances from the GNRs.

Application of low-frequency alternating current electric fields via interdigitated electrodes: effects on cellular viability, cytoplasmic calcium, and osteogenic differentiation of human adipose-derived stem cells.

Electric stimulation is known to initiate signaling pathways and provides a technique to enhance osteogenic differentiation of stem and/or progenitor cells. There are a variety of in vitro stimulation devices to apply electric fields to such cells. Herein, we describe and highlight the use of interdigitated electrodes to characterize signaling pathways and the effect of electric fields on the proliferation and osteogenic differentiation of human adipose-derived stem cells (hASCs).

Nanofibrous composites for tissue engineering applications.

Development of artificial matrices for tissue engineering is a crucial area of research in the field of regenerative medicine. Successful tissue scaffolds, in analogy with the natural mammalian extracellular matrix (ECM), are multi-component, fibrous, and on the nanoscale. In addition, to this key morphology, artificial scaffolds must have mechanical, chemical, surface, and electrical properties that match the ECM or basement membrane of the specific tissue desired.

Dynamics within alkylsiloxane self-assembled monolayers studied by sensitive dielectric spectroscopy.

Self-assembled monolayers are a ubiquitous laboratory tool and have been the subject of many experimental investigations which have primarily focused on static properties of full coverage monolayers, with the maximum density and ordering possible. In this work, dynamics within low density, planar siloxane self-assembled monolayers are studied utilizing highly sensitive dielectric spectroscopy. Dilute, disordered films were intentionally fabricated in order to study the widest range of possible motions.

Fabrication and characterization of electrospun chitosan nanofibers formed via templating with polyethylene oxide.

Chitosan is an abundantly common, naturally occurring, polysaccharide biopolymer. Its biocompatible, biodegradable, and antimicrobial properties have led to significant research toward biological applications such as drug delivery, artificial tissue scaffolds for functional tissue engineering, and wound-healing dressings. For applications such as tissue scaffolding, formation of highly porous mats of nanometer-sized fibers, such as those fabricated via electrospinning, may be quite important.

Structure of submonolayer oleic acid coverages on inorganic aerosol particles: evidence of island formation.

A series of submonolayer deposition studies of oleic acid on both hydrophobic and hydrophilic surfaces has shown that oleic acid self-associates into islands rather than uniformly covering the surfaces. The studies were performed by vapor deposition on 1.6 mum diameter polystyrene aerosol particles as well as on polystyrene and silica surfaces.

Characterization of electrospun nanocomposite scaffolds and biocompatibility with adipose-derived human mesenchymal stem cells.

Electrospun nanocomposite scaffolds were fabricated by encapsulating multi-walled carbon nanotubes (MWNT) in poly (lactic acid) (PLA) nanofibers. Scanning electron microscopy (SEM) confirmed the fabrication of nanofibers, and transmission electron microscopy identified the alignment and dispersion of MWNT along the axis of the fibers. Tensile testing showed an increase in the tensile modulus for a MWNT loading of 0.