Origin of Interface Limitation in Zn(O,S)/CuInS2‑Based Solar Cells

in ACS Applied Materials and Interfaces (2022), 14

Low-Temperature Growth of AlN Films on Magnetostrictive Foils for High-Magnetoelectric-Response Thin-Film Composites

in ACS Applied Materials and Interfaces (2021), 13

Disruption of Electrospinning due to Water Condensation into the Taylor Cone.

in ACS Applied Materials and Interfaces (2020), 12(23), 26566--26576

The well-known problems of electrospinning hygroscopic polymer fibers in humid air are usually attributed to water condensing onto the jet mid-flight: water enters the jet as an additional solvent ... [more ▼]

The well-known problems of electrospinning hygroscopic polymer fibers in humid air are usually attributed to water condensing onto the jet mid-flight: water enters the jet as an additional solvent, hindering solidification into well-defined fibers. Here, we show that fiber fusion and shape loss seen at the end of the process may actually stem from water already condensing into the Taylor cone from where the jet ejects, if the solvent is volatile and miscible with water, for example, ethanol. The addition of water can radically change the solvent character from good to poor, even if water on its own is an acceptable solvent. Moreover, and counterintuitively, the water condensation promotes solvent evaporation because of the release of heat through the phase transition as well as from the exothermic mixing process. The overall result is that the polymer solution develops a gel-like skin around the Taylor cone. The situation is significantly aggravated in the case of coaxial electrospinning to make functional composite fibers if the injected core fluid forms a complex phase diagram with miscibility gaps together with the polymer sheath solvent and the water condensing from the air. The resulting phase separation coagulates the polymer throughout the Taylor cone, as liquid droplets with different compositions nucleate and spread, setting up strong internal flows and concentration gradients. We demonstrate that these cases of uncontrolled polymer coagulation cause rapid Taylor cone deformation, multiple jet ejection, and the inability to spin coaxial fiber mats, illustrated by the example of coaxial electrospinning of an ethanolic polyvinylpyrrolidone solution with a thermotropic liquid crystal core, at varying humidities. [less ▲]

Scanning Probe Photonic Nanojet Lithography

in ACS Applied Materials and Interfaces (2017), 9(37), 32386-32393

The use of nano/microspheres or beads for optical nanolithography is a consolidated technique for achieving subwavelength structures using a cost-effective approach; this method exploits the capability of ... [more ▼]

The use of nano/microspheres or beads for optical nanolithography is a consolidated technique for achieving subwavelength structures using a cost-effective approach; this method exploits the capability of the beads to focus electromagnetic waves into subwavelength beams called photonic nanojets, which are used to expose the photoresist on which the beads are placed. However, this technique has only been used to produce regular patterns based on the spatial arrangement of the beads on the substrate, thus considerably limiting the pool of applications. Here, we present a novel microsphere-based optical lithography technique that offers high subwavelength resolution and the possibility of generating any arbitrary pattern. The presented method consists of a single microsphere embedded in an AFM cantilever, which can be controlled using the AFM motors to write arbitrary patterns with subwavelength resolution (down to 290 nm with a 405 nm laser). The performance of the proposed technique can compete with those of commercial high-resolution standard instruments, with the advantage of a one-order-of-magnitude reduction in costs. This approach paves the way for direct integration of cost-effective, high-resolution optical lithography capabilities into several existing AFM systems. [less ▲]

Design and Fabrication of a Hybrid Superhydrophobic-Hydrophilic Surface That Exhibits Stable Dropwise Condensation

in ACS Applied Materials and Interfaces (2015)