Butterflies, bees and shrimp are the unlikely muses for engineers working on tiny more efficient solar cells, tiny drones and cameras for cancer screenings.
1. Versatile microbot
Engineers at Harvard University have been iterating different versions of their RoboBee hybrid microrobots, and the latest version is able to fly, dive into water, swim, propel itself back out of water and safely land. The latest RoboBee is 1000 times lighter than any previous aerial-to-aquatic robot, at 175 mg total.
This is 90 mg heavier than previous designs, but includes a number of new devices onboard, and the engineers said it could be used for various applications, from search and rescue operations to environmental monitoring and biological studies. The researchers combined theoretical modelling with experimental data and found the Goldilocks combination of wing size and flapping rate.
The robot flaps its wings at 220 to 300 Hz in air, and nine to 13 Hz in water. The key to the robot’s transition from the water into the air is four buoyant outriggers on the RoboBee, plus a central gas collection chamber.
2. Detecting polarisation
A new camera, inspired by the eye of the mantis shrimp, can sense polarisation as well as colour, meaning it can potentially improve early cancer detection and help provide a new understanding of underwater phenomena.
“The animal kingdom is full of creatures with much more sensitive and sophisticated eyes than our own,” said Viktor Gruev, a University of Illinois professor of electrical and computer engineering.
Compared with human vision, which has three different types of colour receptors, the mantis shrimp has 16 different types of colour receptors and six polarisation channels.
“Nature has devised materials such that different colours of light penetrate at different depths,” said Gruev.
“If we shine a blue laser and a red laser on the tip of our finger, we can only observe the red light on the other side of the finger. This is because the red light can penetrate deeper in the tissue.
“Nature has constructed the mantis shrimp eye in such a way that photosensitive elements are vertically stacked on top of each other. His team realised the same laws applied to silicon materials and, by stacking multiple photodiodes on top of each other, they were able to see colour without the use of special filters.”
3. Butterflies inspire more efficient solar cells
Nanostructures inspired by butterfly wings can be added to solar cells, enhancing their light absorption rate by up to 200 per cent. A team from the Karlsruhe Institute of Technology (KIT) in Germany has found that the wings of the butterfly Pachliopta aristolochiae are drilled by nanostructures (nanoholes) that help absorb light over a wide spectrum far better than smooth surfaces.
Dr Hendrik Hölscher of KIT’s Institute of Microstructure Technology reproduced the butterfly’s nanostructures in the silicon absorbing layer of a thin-film solar cell and found, compared to a smooth surface, the absorption rate of perpendicular incident light increased by 97 per cent rising until it reached 207 per cent at an angle of incidence of 50 degrees.
The KIT researchers determined the diameter and arrangement of the nanoholes on the wing of the butterfly by means of scanning electron microscopy. Then, they analysed the rates of light absorption for various hole patterns in a computer simulation. They found that disordered holes of varying diameters, such as those found in the black butterfly, produced most stable absorption rates over the complete spectrum at variable angles of incidence.
4. New THz Detector
Demand for higher bandwidth in wireless communications and depiction for security applications has led to intensified research on systems and components intended for terahertz (THz) frequencies. A new flexible detector for THz frequencies has been developed that can extend the use of terahertz technology to applications that will require flexible electronics, such as wireless sensor networks and wearable technology. The detector uses graphene transistors on plastic substrates.
It was developed by a team at Chalmers University of Technology in Sweden and has a number of unique features. At room temperature, it detects signals in the frequency range 330 to 500 GHz. It is translucent and flexible, and opens to a variety of applications. It may also be of potential benefit in healthcare, imaging sensors for vehicles or wireless communications.
Tech watch is a series where we highlight some of the latest innovations from around the world that flew under the radar. Check back each month for a new batch, or comment below with ones that caught your eye.
