Mimicking the pointed structure of bee hairs and the electrostatic attraction of charged pollen grains to those hairs, Pranavayu, another of Biomimicry Institute’s 2020 Global Design Challenge Finalist, is an air filtration system designed to improve the health and livelihoods of rickshaw drivers in Delhi, India.
Bees moving through the air gather electrostatic charge on their pointed hairs. Pollen can be positively charged and so jumps onto the bee, preventing the need for physical contact. Developed in Utrecht, Netherlands, Pranavayu’s electrostatically charged metal meshes are designed to optimise the capture of pollutants, allowing the driver to breathe clean air.
Air pollution is a serious problem around the world and is often at its worst in developing countries such as India. 21 out of the 30 most polluted cities in the world, for example, are in India. While most forms of transport offer some form of protection, the most vulnerable public transport workers are India’s Rickshaw drivers, particularly those in India’s capital city-Delhi.
According to some scientists, breathing in Delhi is equivalent to 50 cigarettes a day. In 2016 a study was published showing that more than 140 million of India’s inhabitants breathe air that is 10 times worse than the World Health Organization limit. Intermediate solutions such as masks prove to be inefficient owing to their poor reusability and the fact that during smog season, the dark thick smog on the streets also irritates the eyes and skin.
So the need arose for a stable, affordable and sustainable solution to the drivers’ problems. Reducing the risk of respiratory, cardiac, and neurological pathologies to the driver helps meet the third sustainable development goal of ensuring Good Health and Well Being.
The inspiration
Air filtration is a common phenomenon and is well developed throughout the whole living world. Organisms use multiple strategies that can be regrouped in patterns. Drawing inspiration from various such organisms, the design and prototype evolved. Initially, the prototype was informed by the ability of hair to capture pollutants in organisms such as Calanoid copepods and also in camel eyelashes.
The team also incorporated the ability of gills and scales in fish to direct fluid motion, which was the flow of air into the driver’s cabin at this point. The team decided to utilise these gill-like structures to direct airflow toward bristles with hair (possibly with an additional semi-solid substance to act as mucus in the nose). To ensure the removal of the smallest particles, they drew inspiration from the electrostatic attraction of pollen grains onto flower stamens and insect legs.
Electrostatic charge
For wind-pollinated plants, a high electrostatic charge at the tip of the stamen helps to attract the pollen grains to its apex. From here, the pollen grains are transported to the ovary. Similarly, in insect-pollinated plants, the slender legs of these insects maximise the electrostatic charge to attract pollen grains.
This would require pointy structures, preferably on an electrically charged mesh to ensure the removal of every last irritant. However, deeming the bristles to be unsustainable owing to their poor reusability, the team decided to simply repeat patterns they knew to be successful, namely the electrostatic attraction of the pollutants.
They, therefore, relied on a multi-layered system consisting of the charged meshes with protruding needle-like structures to ensure a high charge at the apex and efficiently filter the air.
In a nutshell, the Pranavayu design helps the rickshaw driver breathe clean, non-toxic air. The filter isolates the driver in his cabin and regulate the flow of air into and out of the cabin. The only way for air to enter the cabin is through this filter system. A unidirectional flow of air is ensured by placing two flaps in the part that isolates the driver from the passengers, that open outward. The air that enters through the filter system is rid of its pollutants by electrostatic attraction to the charged meshes.
Unlike standard electrostatic chimneys, since this system is perpetually in motion, only a small voltage is required that can be applied by simply attaching it to the electronic fare meter. The needle- like projections maximise electrostatic charge at their apex, optimising the capture of pollutants. Not only would the design directly benefit the driver by improving his quality of life and ability to earn, but in collaboration with partners such as AIR INK, the team aims to recycle captured pollutants to create a Circular economy.
