3 research outputs found
Testing Self Healing Properties in Polymers
Mussels and barnacles have the ability to stick to underwater surfaces with the help of a cross-linked protein structure. Reduction in the plastic consumption can be achieved by using toughened polymers. Synthesized cross-linking polymers can be used for underwater adhesion by mimicking the protein structure used by mussels and barnacles. One such polymer is poly(3,4-dihydroxystyrene-co-styrene) having enhanced toughness. Traditionally, blister tests measure the adhesion between a substrate to a surface but this was modified to serve as the driving force to drive crack propagation in controlled flaws. The modified blister tests were carried out on polystyrene (PS) samples. Once the method of controlled crack propagation was perfected, the testing was extended to samples of the copolymer of styrene and 3,4-dihydroxystyrene. Samples were made in aluminium pans by solution casting PS in toluene and drying them in an inert oven. Melting PS pellets in the pans directly on a hot plate at 350°F is another way of making samples. The samples were indented with a Vickers micro-hardness tester. Samples were pressurized and changes in crack size and geometry were monitored via optical microscope. The parameters for successful control of crack growth such as sample thickness, air pressure and exposure time were optimized. These parameters will be used to consistently test and study samples for controlled crack growth. This is a part of the ongoing research about toughened polymers
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Artificial phototropism for omnidirectional tracking and harvesting of light.
Many living organisms track light sources and halt their movement when alignment is achieved. This phenomenon, known as phototropism, occurs, for example, when plants self-orient to face the sun throughout the day. Although many artificial smart materials exhibit non-directional, nastic behaviour in response to an external stimulus, no synthetic material can intrinsically detect and accurately track the direction of the stimulus, that is, exhibit tropistic behaviour. Here we report an artificial phototropic system based on nanostructured stimuli-responsive polymers that can aim and align to the incident light direction in the three-dimensions over a broad temperature range. Such adaptive reconfiguration is realized through a built-in feedback loop rooted in the photothermal and mechanical properties of the material. This system is termed a sunflower-like biomimetic omnidirectional tracker (SunBOT). We show that an array of SunBOTs can, in principle, be used in solar vapour generation devices, as it achieves up to a 400% solar energy-harvesting enhancement over non-tropistic materials at oblique illumination angles. The principle behind our SunBOTs is universal and can be extended to many responsive materials and a broad range of stimuli