Everything about Microspheres
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  • Use of Polyethylene Spheres for Analyzing Microplastic Transport in Correlation with Earthworm Presence

    Work by Matthias C. Rillig, Lisa Ziersch, and Stefan Hempel at Freie Universität and Brandenburg Institute of Advanced Biodiversity Research in Berlin has been published in an article titled Microplastic transport in soil by earthworms. This article investigates earthworms effect on microplastic movement into subsurface soil layers.

    Polyethylene Microplastic

    With the increase in plastic usage in recent decades the issue of how this discarded plastic will affect marine environments has been studied extensively. However, effects of microplastics on soil environments have not been tested to the same extent. Scientists have begun testing microplastic movement into lower soil layers by analyzing how differing sized polyethylene beads moved in a 21-day period with and without earthworm facilitation.

    The experiment was designed to confirm the assumption that earthworms would aid in particle movement. Results found earthworms to have a significant positive effect on transporting polyethylene particles from the soil surface. While particle size was also an important factor on the level of transportation into subsurface environments. With polyethylene spheres in the size range 710-850um being significantly more likely to move into the lowest layer when earthworms were present.

    With this experiment showing the ability of earthworms to transport microplastics into subsurface layers more research needs to be done to determine the effects this may have on the soil environment and the worms themselves. Including the multitude of other organisms that could also facilitate similar transportation. As well as the possibilities of microplastics reaching ground water where problems similar to those realized in marine systems could occur.

  • Glass Microspheres Used in Studying Self-Cleaning Gecko-Inspired Adhesives

    Image of Self-cleaning Adhesive of Gecko's Toes

    Image of Self-cleaning Adhesive of Gecko's Toes Source: wikipedia.com

    Researchers from Carnegie Melon University and Karlsruhe Institute of Technology have recently published an article in Journal of the Royal Society titled Staying Sticky: Contact Self-Cleaning of Gecko-Inspired Adhesives that presents the first gecko-inspired adhesive that matches both the attachment and self-cleaning properties of gecko’s foot on a smooth surface.

    Using glass microspheres to simulate contamination the scientists created a synthetic gecko adhesive that could self-clean and recover lost adhesion. Real world applications of self-cleaning adhesives are reusable adhesive tapes, clothing, medical adhesives (bandages) and pick-and-place robots, among others.

    Everyday challenge with traditional adhesives is that they loose their stickiness once contaminated. Geckos have been intriguing researchers for decades because of their unique and striking capability to maintain the stickiness of their toes through contact self-cleaning. They can travel up the walls and ceilings in a wide variety of “dirty” settings retaining adhesion.

    Upon experimentation, scientists discovered that the critical variable is the relative size of microfibers that make up the adhesive compared to the diameter of contaminant particles. Glass microspheres were used in diameters from 3 to 215microns. Glass microspheres were packed in air and used as supplied. Contamination of the samples was achieved by brining each sample in contact with a monolayer of glass microspheres with specific speeds under predetermined compressive loads. The cleaning process involved a load-drag-unload procedure.

    Best self-cleaning results were obtained with the largest contaminants (glass microspheres), with the size of the adhesive fiber much smaller than the contaminating particle. This information is important to know when designing self-cleaning adhesives—make the adhesive fibers much smaller for improved adhesion recovery. This cleaning mechanism requires unloading particles by dragging. The other extreme of contaminating microspheres being much smaller than the adhesive fibers has advantages in some situations, even though it works by a different mechanism. Smaller microspheres tended to become embedded into the adhesive material. Particle embedding is a temporary cleaning process but might be sufficient in some applications.