Development and Application of PP-CNT Composite for Hummingbird Inspired MAV Flapping Wings

Micro Air Vehicles (MAVs) are small unmanned aircrafts which have a maximum size limit of 150 mm in any direction. They can be used for surveillance, reconnaissance, targeting, etc. To perform such missions, MAVs are required to hover. Hummingbirds, having excellent flight characteristics (such as hovering, ability to fly in any direction, ability to produce a reverse camber during upstroke for generating lift in both up-down strokes), have been chosen as the bio-inspiration for wing development. Wings are required to be light, strong and fatigue resistant, to be able to properly flap during flight. Therefore, wing-material becomes a crucial component. An optimization analysis, on the basis of density and fundamental frequency values obtained through Ansys, was done for selecting the wing material. Polypropylene (PP) was observed to have desired properties such as light weight, flexibility, strength, fatigue resistance, good heat and chemical resistance etc. Mixing Carbon Nano Tubes (CNTs) with PP can further increase the strength significantly, making it more suitable for large amplitude flapping. The PP-CNT composites were developed using solution casting method. The films were characterized mechanically (using UTM). The wings were characterized by their structural dynamic properties. The modal analysis of wings was done to obtain natural frequencies and mode shapes. The analysis was aimed to get the fundamental mode in the flapping range (8-15 Hz) of hummingbirds, as resonance increases efficiency. It was also done inside vacuum chamber to observe the effect of air on the natural frequency and modes. The Ansys results were compared with the experiments in vacuum for validation of experimental results. Damping coefficient of wings was also determined. In the end, bio-mimicking of hummingbird wing was also tried by doing some material and structural advancements in the wings

Superhydrophobic PU Sponge Modified by Hydrophobic Silica NPs-Polystyrene Nanocomposite for Oil-Water Separation

In this study, the hydrophobic silica nanoparticles (NPs) are synthesized by simple sol–gel processing of polymethylhydrosiloxane (PMHS). The nanocomposite solution is prepared by adding hydrophobic silica NPs in polystyrene solution and applied on the skeleton of polyurethane sponge by simple immersion-drying process. The as-prepared sponges exhibited superhydrophobic property with water contact angle 161° and oil contact angle nearly 0° and can separate oil from oil–water and oil–muddy water mixture. The superhydrophobic sponge has sustainable anti-wetting property under cross sectional cutting, pressing and twisting, and different pH environment. Such superhydrophobic sponge is suitable for practical application on a large scale.This work is financially supported by DST ? INSPIRE Faculty Scheme, Department of Science and Technology (DST), Govt. of India. [DST/INSPIRE/04/2015/000281]. SSL acknowledges financial assistance from the Henan University, Kaifeng, P. R. China. The authors greatly appreciate the support of the National Natural Science Foundation of China (21950410531).Scopu

Spray Deposition of PDMS/Candle Soot NPs Composite for Self-Cleaning Superhydrophobic Coating

The preparation of superhydrophobic coating using cheap candle soot nanoparticles (CS NPs) collected from candle flame is a very novel research topic. A less than 30 nm sized candle soot particles are collected by passing through stainless steel mesh of pore size ̴30 nm. An optimum suspension of CS NPs and polydimethylsiloxane (PDMS) in chloroform is sprayed on clean glass substrate and dried at 100°C for 1 hour. The coating surface with water contact angle ̴173° and rolling angle ̴ 4° is achieved by spraying suspension of 100 mg CS NPs and 0.3 mL PDMS in chloroform. The stability of superhydrophobic coating is studied by finger-wiping, water jet hitting, water dripping, adhesive tape, and sandpaper abrasion test. Result showed that the coatings prepared with an optimum 100 mg CS NPs in suspension are stable under water jet hitting and water dripping test. The superhydrophobicity is destroyed for four cycles of adhesive tape peeling and seven cycles of sandpaper abrasion tests. The coated substrate showed good self-cleaning performance. The high water repellent and self-cleaning property of the prepared coating can be adopted for industrial applications.This work is financially supported by DST ? INSPIRE Faculty Scheme, Department of Science and Technology (DST), Govt. of India. [DST/INSPIRE/04/2015/000281]. SSL acknowledges financial assistance from the Henan University, Kaifeng, P. R. China. The authors greatly appreciate the support of the National Natural Science Foundation of China (21950410531).Scopu