Tag Archives: Scientific Advances

Butterfly Technology Boosts Solar Panel Output

We normally do not relate butterflies to solar panels. After all, bees and butterflies are good for pollinating flowers and transforming them to fruits so that nature can propagate. On the other hand, solar panels are human creations that collect energy from the sun for the use of humankind. The link between the two seems rather distant, apart from the fact that the sun is the basic force that drives all life on our planet. However, science finds the humble butterfly could be holding the key to unlock new techniques for making solar energy cheaper and more efficient.

Cabbage White butterflies need to heat up their flight muscles before they can take off. Researchers at the University of Exeter have observed that the butterflies adopt a specific posture to maximize solar heat capture. The butterflies position their wings in a V-shape, which, when the researchers adapted for their solar panels, increased the power-to-weight ratio of the panels by about 17 times, making them more efficient.

Scientific Reports, a leading scientific journal has published the research. The research team contained members from both the Centre for Ecology and Conservation and the Environment and Sustainability Institute, based at the University of Exeter in the Penryn Campus in Cornwall. According to Tapas Mallick, the lead author of the research, although bio mimicry is popular in engineering, such unparalleled multidisciplinary research is opening pathways for developing low cost solar panels.

Butterflies usually depend on the sun to heat up their flight muscles before they can take off. However, researchers found the Cabbage White butterflies taking flight before other butterflies did, even on cloudy days. The energy from the sun is limited on cloudy days, forcing insects to make maximum use of the available energy to heat up their flight muscles.

Researchers observed that Cabbage White butterflies adopted a v-shaped posture, known as reflectance basking. That allows the butterflies to maximize the concentration of solar energy onto their thorax, so necessary for fast heating up the flight muscles. The wings of the butterflies have a specific sub-structure that allows maximum light from the sun to be most efficiently reflected onto their muscles, which warm up to the optimal temperature as quickly as possible.

The scientists then investigated the process of replication of the butterfly wings for developing a new, lightweight reflective material solar energy products could use. They found that by replicating the simple monolayer of scale cells on the butterfly wings, they could optimize the power-to weight ration of solar concentrators. That made the solar cells lighter and more efficient.

The team also found the optimal angle at which the butterfly held its wings. When the butterflies tilted their wings by about 17 degrees to the body, they were able to increase the temperature of their bodies by 7.3°C more than when they held their wings flat. By positioning the reflectors at 17 degrees within the solar cells, researchers found the output from the solar cells increased by 50 times.

Therefore, by studying the manner in which the lowly butterfly maximized its use of solar energy, scientists could not only double the output of their solar cells. They were also able to improve its power-to-weight ratio significantly.

Quadriplegics Can Control Exoskeletons with Their Brain

Artificial limbs help people who have lost a part of their arms or legs to regain partial functionality of their extremities. However, for those who have lost control of a major part of their bodies and thus rendered quadriplegic, artificial limbs are not of much use. For addressing such and other whole-body disabilities, exoskeletons are showing great promise.

Scientists working at the Technische Universitat Berlin and Korea University are creating such lower-limb exoskeletons. The control system here is completely hands-free. Rather, it is a brain-to-computer interface, which controls the exoskeleton, by decoding and making use of signals from the wearer’s brain. According to the researchers, volunteers who were given the exoskeleton to use took only a few minutes for learning to operate the system. Therefore, substantially paralyzed people may hope to walk again with the help of this exoskeleton.

Research on such exoskeleton systems is not new and several types are in development and in limited production in many parts of the world. However, most achieve controls by detecting subtle movements in the upper body of the wearer. However, the difference in the KU/TU Berlin unit is the control is entirely dependent on brain signals. Therefore, this is useable even by a completely paralyzed person.

The human brain generates different signals when the person stares at a specific LED. These signals are detected and interpreted to be used for controlling the hands-free exoskeleton. An EEG brain control interface connects wirelessly to the main computer of the control system.

In actual practice, the wearer stares at any one of five flashing LEDs. This initiates waves in the wearer’s brain and an electroencephalogram or EEG worn as a cap reads the signals. Because each LED flashes at a different rate, focusing on any one at a time produces a specific signal pattern in the brain of the user corresponding to a desired mode of movement. The computer system interprets the readings of these signals sent to it from the EEG cap and converts them to system instructions for operating the exoskeleton.

As this method of control does not require detection of movement from any other body part, it is eminently suitable for even those who have lost the capacity for voluntary body control, except for eye movements. Ordinarily, such people would not be able to use or control a standard exoskeleton. According to the researchers, their system has a much better signal-to noise ratio.

The brain generates signals depending on external signals it receives from its surroundings. This acts like noise to the actual control signal desired for movement. By concentrating on a flashing LED, the researchers are effectively separating the user’s brain control signals from being cluttered with external stimuli. The result is a more accurate exoskeleton operation than what a conventional hard-wired system could have achieved.

Exoskeleton systems are notorious for creating loss of electrical noise, especially affecting the EEG signals. However, the frequency of the flickering LED acts as a filter to separate the EEG signal effectively. This exoskeleton system helps people with high spinal cord injuries or those with motor neuron disease who face difficulties in communicating or using their limbs.

Liquid Droplets That Levitate On a Blue Light Pad

Scientists in France have found a novel technique to levitate liquid droplets on a cushion or pad of blue light. The effect sets off a striking light show with the droplets generating sparks as they drift over the blue gap.

The effect is quite like the Leidenfrost Levitation in which a liquid drop is made to levitate on its vapor layer created over a hot surface. However, while in the Leidenfrost effect, the temperature is the initiating factor, here it is electricity creating the interesting spectacle.

Plasma creation

The researchers discovered that a high pulse of electricity applied to a gas could vaporize it so the gas glows with a bluish light. This remarkable find may present an economical technique to produce movable micro plasma layers. Furthermore, the study yields remarkable insights into basic principles of physics.

Physicist Cedric Poulain of French Alternative Energies and Atomic Energy Commission explains that the technique is a simple and an innovative way to create plasma.

In the experiment tried out by the research workers, over 50 volts of electric power was applied across a droplet of dilute hydrochloric acid suspended above a metallic plate. This made the droplet levitate over a region radiating a light blue glow.

Cushion of vapor

At voltages above 50V, the base of the acid droplet started to produce sparks. The drop rose, increasing the gap above the metal plate and a blue light filled up the gap. The scientists first assumed that the droplet was lying on a cushion of gaseous hydrogen produced by the electrolysis of the acidified water. Further scientific analysis established that the gas cushion primarily consisted of water vapor.

Poulain explained that extremely small space between the metal plate and the droplet makes it easy to set up the high electric field needed to produce the plasma layer, even with moderate electric voltages.

Contrasting boiling with electrolysis of water

The team compared the electrolytic dissociation of water with boiling. Poulain brought forward the example of a water drop placed on the surface of a heated vessel. He pointed out that at temperatures higher than 100 degrees Centigrade, the drop spreads out and bubbles form on the surface. At temperatures exceeding 280 degrees Centigrade, a vapor cushion can be seen forming in between the drop and the vessel surface. This makes the water drop levitate so that there is no contact between the drop and the vessel surface.

The team described the transition in electrolysis as somewhat similar.

Figuring out the blue light phenomenon

According to the team of researchers working on the project, the emission of blue light was the most striking feature of the study. For a proper conception of the phenomenon, the scientists plan to explore the makeup of the plasma layer. They believe that two types of plasma are superposed, though they cannot yet understand the effect.

The scientists also intend to scrutinize the liquid dynamics at the lower surface of the droplet when the sparks just start to fly out. This should give further information regarding the nature of the plasma layer.