Colin R. Crick

Robust self-cleaning surfaces that function when exposed to either air or oil

A robust paintlike repellent coating Superhydrophobic materials often depend on a particular surface patterning or an applied coating. However, these surfaces can be damaged by wear or fouled by oily materials. Lu et al. devised a suspension of coated titanium dioxide nanoparticles that can be spray-painted or dipcoated onto a range of hard and soft surfaces, including paper, cloth, and glass. The coatings resisted rubbing, scratching, and surface contamination. Science, this issue p. 1132 Robust, coated self-cleaning surfaces function after either abrasion or oil contamination. Superhydrophobic self-cleaning surfaces are based on the surface micro/nanomorphologies; however, such surfaces are mechanically weak and stop functioning when exposed to oil. We have created an ethanolic suspension of perfluorosilane-coated titanium dioxide nanoparticles that forms a paint that can be sprayed, dipped, or extruded onto both hard and soft materials to create a self-cleaning surface that functions even upon emersion in oil. Commercial adhesives were used to bond the paint to various substrates and promote robustness. These surfaces maintained their water repellency after finger-wipe, knife-scratch, and even 40 abrasion cycles with sandpaper. The formulations developed can be used on clothes, paper, glass, and steel for a myriad of self-cleaning applications.

Preparation and Characterisation of Super-Hydrophobic Surfaces

The interest in highly water-repellent surfaces has grown in recent years due to the desire for self-cleaning surfaces. A super-hydrophobic surface is one that achieves a water contact angle of 150 degrees or greater. This article explores the different approaches used to construct super-hydrophobic surfaces and identifies the key properties of each surface that contribute to its hydrophobicity. The models used to describe surface interaction with water are considered, with attention directed to the methods of contact angle analysis. A summary describing the different routes to hydrophobicity is also given.

Superhydrophobic polymer-coated copper-mesh; membranes for highly efficient oil–water separation

A novel filtration system has been developed for the separation of water and hydrophobic solvents. Copper meshes of various pore diameter (297, 251, 178 and 152 μm) were coated with extremely rough silicone elastomer films. Depositions of this polymer were carried out by aerosol assisted chemical vapour deposition. The polymer coating rendered all meshes superhydrophobic, with static water contact angles of 152–167° depending on mesh diameter. The meshes were found to be exceptionally efficient in separating organic solvents (hexane, petroleum ether and toluene) from water. The dual-layered filtration system developed focuses on directing the transport of oil away from water with the highest efficiency. The device provides a scalable solution to many challenges, including microanalysis, filtration and chemical processing.

Superhydrophobic Photocatalytic Surfaces through Direct Incorporation of Titania Nanoparticles into a Polymer Matrix by Aerosol Assisted Chemical Vapor Deposition

A new class of superhydrophobic photocatalytic surfaces that are self-cleaning through light-induced photodegradation and the Lotus effect are presented. The films are formed in a single-step aerosol-assisted chemical vapor deposition (AACVD) process. The films are durable and show no degradation on continuous exposure to UV-C radiation.

A general method for the incorporation of nanoparticles into superhydrophobic films by aerosol assisted chemical vapour deposition

A general method for the synthesis of a novel class of superhydrophobic polymer thin films with embedded nanoparticles is presented. These materials combine the superhydrophobic nature of silicone polymer matrices and the properties of the nanoparticles for photocatalysis, magnetic applications, or high surface area catalysis. The films themselves are deposited using a one-pot aerosol assisted chemical vapour deposition (AACVD) process, and are characterised using electron microscopy, X-ray dispersive spectroscopy, water contact angle and bouncing measurements and elemental mapping. We show that these materials demonstrate multifunctional behaviour through magnetic, catalytic and superhydrophobic measurements.

CVD of copper and copper oxide thin films via the in situ reduction of copper (II) nitrate-a route to conformal superhydrophobic coatings

The use of copper organometallics is an established route to generate thin films of copper. This paper describes the deposition of copper and copper(I) oxide films using relatively inexpensive copper nitrate solutions in a facile aerosol assisted chemical vapour deposition process. The composition of the resultant thin film was dependant on the solvent used and temperature of deposition, with evidence to suggest an in situ production of hydrogen which protects the copper films from oxidation. The metallic copper films were subsequently modified by oxidation to copper hydroxide and functionalised with a fluorinated thiol. The treated films were extremely hydrophobic with water contact angles that approached 180° and a less than 1° tilt angle, this a product of the extremely rough and low energy surface. The conformal substrate coverage achieved with this technique could be implemented for uniform metallic, semiconductor, hydrophilic or superhydrophobic coatings.

Precise attoliter temperature control of nanopore sensors using a nanoplasmonic bullseye.

Targeted temperature control in nanopores is greatly important in further understanding biological molecules. Such control would extend the range of examinable molecules and facilitate advanced analysis, including the characterization of temperature-dependent molecule conformations. The work presented within details well-defined plasmonic gold bullseye and silicon nitride nanopore membranes. The bullseye nanoantennae are designed and optimized using simulations and theoretical calculations for interaction with 632.8 nm laser light. Laser heating was monitored experimentally through nanopore conductance measurements. The precise heating of nanopores is demonstrated while minimizing the accumulation of heat in the surrounding membrane material.

Superhydrophobic Surfaces as an On-Chip Microfluidic Toolkit for Total Droplet Control

We propose and outline a novel technique designed to utilize the unique surface repulsion present between aqueous droplets and customizable superhydrophobic surfaces for the on-chip spatial and temporal manipulation of droplets within microfluidic architectures. Through the integration of carefully designed and prepatterned superhydrophobic surfaces into polymer microfluidic chipsets, it is possible to take advantage of this enhanced surface repulsion to passively manipulate droplets on the microscale for a wide range of droplet operations, including but not limited to acceleration, deceleration, merging, and path control. This work aims to help fulfill and stimulate development based around current requirements for additional passive analytical manipulation and detection techniques in order to enable a reduction in experimental design complexity with the goal of facilitating and improving portability for Lab-on-a-chip devices.

Ambipolar Transport in Solution-Synthesized Graphene Nanoribbons

Graphene nanoribbons (GNRs) with robust electronic band gaps are promising candidate materials for nanometer-scale electronic circuits. Realizing their full potential, however, will depend on the ability to access GNRs with prescribed widths and edge structures and an understanding of their fundamental electronic properties. We report field-effect devices exhibiting ambipolar transport in accumulation mode composed of solution-synthesized GNRs with straight armchair edges. Temperature-dependent electrical measurements specify thermally activated charge transport, which we attribute to inter-ribbon hopping. With access to structurally precise materials in practical quantities and by overcoming processing difficulties in making electrical contacts to these materials, we have demonstrated critical steps toward nanoelectric devices based on solution-synthesized GNRs.

Superhydrophobic silica films on glass formed by hydrolysis of an acidic aerosol of tetraethylorthosilicate

Silica microparticle films were deposited using a new hybrid chemical vapour deposition process. The combination of gaseous tetraethylorthosilicate (TEOS) and an acidic aerosol resulted in the acid catalysis of TEOS, this produced silica microparticles which then deposited onto a glass substrate to form a continuous film. The microparticle films as formed were exceptionally rough and superhydrophilic, with water contact angles below 5°. The size of microparticles in the films could be controlled by varying the temperature at which they were deposited. The surface silanol groups of the hydrophilic films could then be functionalised using hexamethyldisilazane to form trimethylsiloxane groups. The resultant surface showed extreme hydrophobicity with water contact angles approaching 180° and a contact angle hysteresis near to zero. The functionalised silica films also demonstrated an elastic bounce of water droplets dropped onto the surface.