‘T-ray specs’ that bestow on wearer Superman-like power to see through clothing now a step closer to reality

Scientists find way of downsizing detectors of terahertz radiation but say wearable glasses could still be years away

PUBLISHED : Monday, 14 December, 2015, 8:01am
UPDATED : Thursday, 08 March, 2018, 6:05pm

A tiny terahertz detector developed by a team of Chinese scientists may have brought glasses that can see through clothing, or certain materials like cardboard and paper, a step closer to reality, according to their recently published paper in the journal Advanced Materials.

The effect of the glasses would be similar to Superman’s X-ray vision, but safer for human use.

One key difference is that it relies on an alternative form of radiation - one that can penetrate certain non-conducting materials but not, for example, metal or water.

The radiation emitted by X-rays is in some ways too powerful and potentially harmful as it can cause cell mutations that may lead to cancer.

In contrast, so-called T-rays, which fall in a lower range of the electromagnetic spectrum between infrared and microwave radiation, are weaker and therefore safer.

READ MORE: ‘X-rays can be a double-edged sword’: Radiation also found to have beneficial effect of boosting cell’s batteries to slow ageing

Scientists have been studying terahertz radiation for decades. But the equipment used to detect them remains bulky and sometimes requires an entire room to house and several technicians to carry out a series of complex operations.

This is because the equipment relies on sensors kept in an extremely cold environment. When the radiation comes into contact with these, it disturbs a small number of atoms and releases heat. But the amount of heat generated is so tiny it can only be detected in extreme cold.

The Chinese team, led by Professor Huang Zhiming at the Chinese Academy of Sciences’ Shanghai Institute of Technical Physics, took a different approach.

They built a “trap” to catch the elusive T-rays using a semiconductor sandwiched between two metal plates. When the radiation hit the thin film, it generated what is known as an antisymmetric electromagnetic wave. This wave then drew electrons away from the metal plates to create an electric current.

As this form of radiation cannot be measured digitally using electronic counters - it exists at too high a frequency on the electromagnetic spectrum - scientists have to adopt such proxy measures.

In this case, by measuring the currents, the team was able to reproduce the exact patterns of the rays using fixed algorithms.

Huang said the signifiance of the breakthrough was that the detector used was the size of a grain of rice, meaning it could easily be attached to a mobile device or a pair of “smart” glasses.

Compared to previous room-sized detectors, it was equally sensitive but 1,000 times faster, he added.

Speed is important because of the time lag between the moment the rays hit the sensor and the output of results. Shorter intervals thus facilitate better and more accurate monitoring.

Similar breakthroughs have been reported by other teams in recent years using different materials.

A team of scientists from the California Institute of Technology (CalTech) earlier reported the development of a grain-size silicon chip that can detect T-rays. Another team with the University of Michigan built a separate chip using carbon nanotubes.

The recent advancements suggested that the use of T-rays in the medical sector as a replacement for X-rays or consumer-grade products may be closer than previously thought, according to Huang.

But he predicts that at least another decade is needed before the first pair of “T-ray specs” hit the shelves as various technical obstacles remain, including the source device.

To penetrate cloth, such glasses would need to emit a radar-like beam so the electromagnetic waves would bounce back and be detected.

READ MORE: Hong Kong’s background radiation levels ‘astounding’, says former top official

Until the latest finding, scientists had been unable to make a source device small enough to be fit into a mobile gadget.

They also had to work out other issues such as power supply, as generating T-rays requires lots of energy - way beyond the capacity of a smartphone battery.

But Huang was optimistic about the future development of the technology, partly due to its high potential for military use.

Given a powerful enough source device, T-rays could be used by radar to detect stealth aircraft, or used by military satellites to transmit huge amounts of data.

Huang said that T-ray radars can already “see” objects a kilometre away on a clear day. He expected the range to be extended significantly in the future.