For many years, two-dimensional nanomaterials with a thickness of only one or a few atoms have been all the rage in the field of materials science. Take graphene as an example. This kind of material produced by single-layer carbon atoms is hundreds of times stronger than steel, with high conductivity and super flexibility.

Oscar Vazquez-Mena, a professor of nanoengineering at the Jacob School of Engineering at the University of California, San Diego, is pushing these types of materials to new heights. His research focuses on integrating different nanomaterials in 3D to create new devices for environmental monitoring, energy collection and biomedical applications. Vazquez Mena recently won a five-year career award worth $500,000 for such projects of the National Research Foundation.

The project involves combining graphene with semiconductor nanoparticles called quantum dots to create devices that can "see" light with different wavelengths (such as infrared and ultraviolet) invisible to human eyes. These devices, called multispectral photodetectors, allow cameras to take pictures of infections, toxic gases and harmful radiation. Check food quality or pollution; And monitor the quality of air and water. They can also help their eyesight at night and when it is foggy.

Chip integrating graphene and quantum dots.

Vazquez-Mena method will make these devices ultra-thin. He said: "As we are using nanomaterials, in principle, we can design a very thin photodetector with a thickness of about 65,438+0 microns, which can be easily integrated into smart phones and other mobile devices for deployment outside the laboratory."

Imaging the brain with ultrasound

In another project, Vazquez-Mena is stacking nanostructures to build a 3D array, which can make ultrasound pass through the skull, non-invasively image and stimulate the human brain. This technology will be very helpful to treat brain diseases and trauma without opening the skull or inserting wires and implants into the brain. It also allows doctors to quickly diagnose patients' brain injuries without having to perform expensive MRI scans.

It is not easy to let ultrasound pass through the skull and enter the brain. The human skull is thick and dense, so it can reflect or absorb ultrasonic waves before sending them to the brain.

In order to overcome this obstacle, Vazquez-Mena is designing a special material called metamaterial, which is composed of nano-structures, which can counteract the reflection generated by the skull and fundamentally change the direction of ultrasonic waves passing through the skull. Metamaterials are composed of silicon nitride and micron-scale acoustic cavity nano-films. These two components are arranged together in the form of a 3D array, which enables the material to manipulate sound waves in a way that traditional materials cannot.

Vazquez-Mena said, "This is another example of building 3D structures based on nanomaterials, which can realize exciting new functions."