Nanowires are 10,000 times thinner than a human hair, but show promise as components of small-scale electrical devices. This article outlines a few of the developments in nanowire technology which bring us closer to their mainstream use in a variety of sensors and solar power generators.

Gallium arsenide (GaAs) nanowires

Credit: University of the Philippines Diliman

Looking to improve nanowire-based renewable energy production is a group headed by Dr Armando Somintac at the University of the Philippines Diliman. Their work focuses on gallium arsenide (GaAs) nanowires, which have various applications in electronics, including solar cells. GaAs nanowires can have cubic or hexagonal crystal structures; cubic crystal structures are better for electronics, but current production techniques result in a mixture of the two. The researchers are using gold catalysts to enhance growth of GaAs nanowires, and expect the resulting wires to have mainly cubic crystals. With this work, they hope to shed light on the optimal conditions for GaAs nanowire production.

 
Aligning nanowires vertically

Credit: Korea Research Institute of Standards and Science

 

Nanowires also have potential in other types of sensors, and scientists at the Korea Research Institute of Standards and Science have developed technology that could be used in sensors of disease, drugs or explosives, as well as in solar power generators. The group developed a way to align nanowires vertically on a substrate rather than horizontally and still achieve reliable electrical contact. This maximises the number of nanowires on a given surface area of the substrate, increasing the efficiency of electrical conductance.
Similar work by researchers in Singapore and Korea has maximised the performance of vertically-aligned nanowires in thermoelectric power generators. An array of vertical nanowires requires a filling material to provide support, and previous work had used silicon oxide. The new research shows that using polyimide instead allows more heat to flow through the wires, and reduces damage, resulting in a doubling of performance. The work is one step towards the use of silicon nanowire-based thermoelectric power generators as miniaturised clean energy sources.

 

Artificial blood vessel

Researchers at the A*STAR’s Institute of Microelectronics (IME), Seoul National University of Science and Technology and the National University of Singapore and are developing a new type of artificial blood vessel that has in-built pressure sensors, and have shown that silicon nanowires are ideal as the pressure-sensitive element. These nanowires are piezoresistive, meaning that the amount of electricity they conduct changes according to the mechanical pressure that they’re under. The team optimised the length and arrangement of the silicon nanowires, producing sensors 15 times more sensitive than in previous work. The nanowires could also withstand sufficient pressure for use in biomedical monitoring.

 

For further information contact:
Artificial blood vessel
Cairan He (technical)
Institute of Microelectronics (IME)
Agency for Science, Technology and Research (A*STAR), Singapore
Email: hec@ime.a-star.edu.sg
 
Benjamin Chua Soo Yeng (clinical)
Institute of Microelectronics (IME)
Agency for Science, Technology and Research (A*STAR), Singapore
Email: surcsyb@nuhs.edu.sg
 
Aligning nanowires vertically
Dr Woo Lee
Korea Research Institute of Standards and Science (KRISS), South Korea
E-mail: woolee@kriss.re.kr
Gallium arsenide (GaAs) nanowires
Dr. Armando S. Somintac
National Institute of Physics
University of the Philippines Diliman
Email: somintac@gmail.com