Optically transparent, mechanically durable, and self-cleaning superhydrophobic coatings are greatly awaited for applications in daily life. An attempt has been made to develop sol–gel processed semi-transparent, durable and self-cleaning superhydrophobic coatings on glass using a silica–PMMA composite. A water drop acquires a near spherical shape on the coating exhibiting a water contact angle of ∼159° and immediately rolled off under small disturbance. A 10 μl water drop could individually collect around 10 mg of dirt particles along the way whilst rolling off the coating surface. The superhydrophobicity of the coatings remained intact under the impact of a water jet. A water jet hits the superhydrophobic coating and was repelled straightaway off the surface, without leaving any trace of water. These coatings showed both strong superhydrophobicity and superoleophilicity. We observed an improvement in mechanical stability, as well as optical transparency of the coatings in the visible range after low loadings of PMMA polymer (2 vol%) in silica. The prepared coatings maintained excellent superhydrophobicity even after 6 months storage under normal conditions in air.

Development of sol–gel processed semi-transparent and self-cleaning superhydrophobic coatings

Polycaprolactone/Polymethylmethacrylate (PCL/PMMA) biopolymer blend can be prepared by casting technique. Structural, optical and thermal properties of the blend have been studied using X-ray diffr...

Spectroscopic studies and thermal properties of PCL/PMMA biopolymer blend

Polymer blends yield carbon materials with superior performances for supercapacitor applications since blending can lead to controlled and fine pore architectures. In this study, a supercapacitor electrode material derived from an immiscible polymer blend comprising polyacrylonitrile (PAN) and polymethyl methacrylate (PMMA) was investigated. PAN was used as the carbonizing polymer while PMMA was used as the sacrificial polymer. The polymer blend solutions in DMF were electrospun to obtain freestanding nanofiber mats. The resulting mat was carbonized and activated by CO2 at 1000 °C to obtain porous carbon nanofibers (CNFs), as PAN converts to carbon and the sacrificial polymer decomposes creating pores. We demonstrated that the pore sizes can be tuned by varying the amount of PMMA loading in the blend compositions. PAN : PMMA (95 : 5), was found to be the optimum blend composition, affording the highest surface area of 2419 m2 g−1, higher degree of graphitization, higher carbon yield and lower charge transfer resistance among the blend compositions studied. Furthermore, the PAN : PMMA (95 : 5) CNFs showed the highest capacitance of 140 F g−1 and energy densities of 67 W h kg−1 at 3.5 V and 101 W h kg−1 at 4 V in an ionic electrolyte (EMITFSI) and also showed good cycling stability with 85% capacitance retention after 1000 cycles.

Supercapacitor performance of carbon nanofiber electrodes derived from immiscible PAN/PMMA polymer blends

We present a facile, low-cost and cleanroom-free technique for the fabrication of microneedles using molds created by laser ablation. Microneedle mold with high aspect ratios is achieved on acrylic sheet by engraving a specific pattern of crossover lines (COL) using CO2 laser cutter. Ablating COL pattern on the acrylic sheet creates a sharp conical shape in the center of the design. We have shown that a variety of microneedle shapes with different heights and tip angles can be easily achieved by changing the number and the length of the COL. Polydimethylsiloxane (PDMS) microneedles were fabricated by casting the PDMS on the mold. The resulted PDMS microneedles are oxygen plasma treated and then silanized. Another PDMS layer is casted on PDMS microneedles and detached after curing. The silanization prevents those two layers of PDMS from bonding to each other and makes them easily detachable. After detachment of the PDMS mold of microneedles, the mold is used to fabricate degradable polyvinyl alcohol microneedle patch suitable for transdermal drug delivery. The release kinetics of the needles are also shown and discussed in order to prove the applicability of the needles. A low-cost method to make microneedles for non-invasive drug delivery across the skin has been devised by a team in the United States. By forming microchannels in the skin, microneedles allow drugs such as insulin to be administered without a painful injection and with improved efficacy. However, conventional methods for fabricating microneedles are expensive, requiring cleanroom facilities. Sameer Sonkusale and co-workers at Tufts University have developed a method that does not require a cleanroom. They use a laser cutter to fabricate molds for microneedles in an acrylic sheet. The cone-shaped molds are created by passing the laser beam through the same point but by different paths, resulting in the greatest amount of material being removed from the central point. The researchers demonstrate their mold by making degradable microneedle patch from various polymers.

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Low-cost and cleanroom-free fabrication of microneedles

A facile solution combustion synthesis has been adopted to synthesize ZrO2/CuO nanocomposite oxides (NCO’s) by utilizing Oxalyl dihydrazide (ODH) as fuel. The X-ray diffraction patterns and TEM analysis reveals the presence of cubic ZrO2 and CuO in ZrO2/CuO NCO’s. The NCO’s synthesized by simple, fast, highly sensitive and low-cost method is found to be an alternate to traditional luminescent powders for the detection and enhancement of finger marks in a broad range of surfaces. The photoluminescence analysis indicates that the present NCO is an effective blue component in display applications. The synthesized ZrO2/CuO (2:1) composite exhibited excellent photocatalytic activity towards the degradation of various dyes under Sunlight. In particular, Indigo carmine dye was chosen to explore the photocatalytic performance of prepared NCO’s under Sunlight illumination. It was found that ZrO2:CuO (2:1) NCO showed enhanced photocatalytic activity of 97% which was found to be 3.3 times 2.4 times and 1.5 times higher than that of pure ZrO2, CuO and commercial P25. This can be mainly attributed to the balance between the parameters, band gap, nature of morphology, crystallite size, defects and surface area which causes a slow electron-hole pair recombination rate with fast electron transfer ability. It opens new window to use this simple method to synthesize multifunctional character ZrO2-based composite materials in the area of photocatalysis particularly waste water treatment, display applications as well as a labeling agent to enhance latent fingerprints.

A simple combustion method for the synthesis of multi-functional ZrO2/CuO nanocomposites: Excellent performance as Sunlight photocatalysts and enhanced latent fingerprint detection

Superfine powders of poly (methyl methacrylate) (PMMA) have been prepared by means of an emulsion polymerization method. These have been used as templates in the synthesis of tetragonal phase mesoporous zirconia by the sol–gel method, using zirconium oxychloride and oxalic acid as raw materials. The products have been characterized by infrared spectroscopy, X-ray diffraction analysis, transmission electron microscopy, N2adsorption-desorption isotherms, and pore size distribution. The results indicate that the average pore size was found to be 3.7 nm.

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Chunxiang Zhang

Papers

Preparation and Characterization of Mesoporous Zirconia Made by Using a Poly (methyl methacrylate) Template