Three-Dimensional Deposits from Drying Particle-Laden Drops.

Formation of inhomogeneous (in the form of a "coffee ring") or homogeneous deposits accompanies the drying of a particle-laden drop. Invariably, this deposition occurs in a two-dimensional (2D) space (, plane) (and might have a finite thickness in ), where the evaporating drop is positioned. Here, we show an interesting extension of this problem: we demonstrate the occurrence of evaporation-mediated particle deposits that span three dimensions (, , and ).

Direct visualization of nanoparticle morphology in thermally sintered nanoparticle ink traces and the relationship among nanoparticle morphology, incomplete polymer removal, and trace conductivity.

A key challenge encountered by printed electronics is that the conductivity of sintered metal nanoparticle (NP) traces is always several times smaller than the bulk metal conductivity. Identifying the relative roles of the voids and the residual polymers on NP surfaces in sintered NP traces, in determining such reduced conductivity, is essential. In this paper, we employ a combination of electron microscopy imaging and detailed simulations to quantify the relative roles of such voids and residual polymers in the conductivity of sintered traces of a commercial (Novacentrix) silver nanoparticle-based ink.

Applications, fluid mechanics, and colloidal science of carbon-nanotube-based 3D printable inks.

Additive manufacturing, also known as 3D printing (3DP), is a novel and developing technology, which has a wide range of industrial and scientific applications. This technology has continuously progressed over the past several decades, with improvement in productivity, resolution of the printed features, achievement of more and more complex shapes and topographies, scalability of the printed components and devices, and discovery of new printing materials with multi-functional capabilities. Among these newly developed printing materials, carbon-nanotubes (CNT) based inks, with their remarkable mechanical, electrical, and thermal properties, have emerged as an extremely attractive option.

Ultrathin and Ultrasensitive Printed Carbon Nanotube-Based Temperature Sensors Capable of Repeated Uses on Surfaces of Widely Varying Curvatures and Wettabilities.

In this paper, we demonstrate the ability to fabricate temperature sensors by using our newly developed carbon nanotube-graphene oxide (CNT-GO) ink to print temperature-sensitive traces on highly flexible, thin, and adhesive PET (polyethylene terephthalate) tapes, which in turn are integrated on surfaces of different curvatures and wettabilities. Therefore, the strategy provides a facile, low-cost, and environmentally friendly method to deploy printed temperature sensors on surfaces of widely varying curvatures and wettabilities. The temperature sensing occurs through a thermally induced change in the resistance of the printed traces and we quantify the corresponding negative temperature coefficient of resistance (α) for different conditions of curvatures and wettabilities.

Shape-driven arrest of coffee stain effect drives the fabrication of carbon-nanotube-graphene-oxide inks for printing embedded structures and temperature sensors.

Carbon nanotube (CNT) based binder-free, syringe-printable inks, with graphene oxide (GO) being used as the dispersant, have been designed and developed. We discovered that the printability of the ink is directly attributed to the uniform deposition of the GO-CNT agglomerates, as opposed to the 'coffee-staining' despite these aggregates being micron-sized. The ellipsoidal nature of the micron-scale GO-CNT agglomerates/particles enables these particles to severely perturb the air-water interface, triggering a large long-range capillary interaction that causes the uniform deposition by overcoming the "coffee-stain"-forming forces from the evaporation-mediated flows.

A "flared-end" gradient coil with outer-wall direct cooling for human brain imaging: A feasibility study.

Optimal gradient performance is arguably a pre-requisite to realize the full potential of ultrahigh field magnetic resonance imaging (MRI). The values of using tailored gradient coils for brain imaging have been well acknowledged. Unfortunately, conventional head-only gradient coils have two major technical limitations, i.