This past September, we reported on research out of Vanderbilt University, in Nashville, in which nanowires were used to create the first integrated circularly polarized light (CPL) detector on a silicon chip that could ultimately lead to portable sensors for drug screening—or even enable quantum computers.
Now, researchers at the University of Michigan, in Ann Arbor, have continued this miniaturization of CPL detectors by developing a flexible nanocomposite circularly polarized-light detector that they claim could lead to the development of a cellphone-size cancer detector.
As a primer on how circularly polarized light can enable detectors of cancer—or whatever else a device has been designed to discern—here’s a paragraph from a post on this blog from September:
Polarized light comes in basically two forms—linear or circular. In contrast to non-polarized light, in which the electric fields of the photons are oriented in random directions, polarized light, whether linear or circular, features electric fields oriented in a single plane. (With circularly polarized light, the plane is continually rotating through 360 degrees.) One of the distinguishing capabilities of circularly polarized light is that it can discern the difference between right-handed and left-handed versions of molecules—a property known as chirality.
In this latest research out of Michigan, which was explained in a paper published in the journal Nature Materials, the researchers fabricated the nanocomposites by taking twisted elastic substrates and coating them with films made of plasmonic nanocolloids. Colloids are simply a solution in which the substances (in this case, nanoparticles) suspended in it remain evenly dispersed; and, plasmonics looks at how free electrons in a metal (in this case, the gold nanoparticles) can be excited by photons from light to create collective oscillations in the electrons.
“This film is light, flexible and easy to manufacture,” said Nicholas Kotov, who led the research, in a press release. “It creates many new possible applications for circularly polarized light, of which cancer detection is just one.”
In the detection of cancer, circularly polarized light is used to identify biomarkers, such as specific proteins and pieces of DNA which are present in the blood at the first stages of cancer. To ferret out the biomarkers, synthetic biological particles are used to attract them. When these particles—which are coated with a reflective layer that reacts to the circularly polarized light—are added to a blood sample, they attach themselves to the biomarkers. This makes the cancer indicators relatively easy to spot by clinicians when they shine circularly polarized light on the sample.
While this sounds great, the problem today is that producing the circularly polarized light requires a large, expensive, and elaborate apparatus. The Michigan researchers believe that their flexible nanocomposite can generate circularly polarized light in a simple and inexpensive way. The eventual result, they say, could be a handheld device capable of identifying blood samples quickly and providing more frequent testing.
“More frequent monitoring could enable doctors to catch cancer recurrence earlier, to more effectively monitor the effectiveness of medications and to give patients better peace of mind,” added Kotov. “This new film may help make that happen.”
In contrast to the CPL detector developed at Vanderbilt last year, this Michigan CPL detector is flexible. When stretched, the nanocomposite changes the polarization of light that passes through it instantly, thereby allowing the clinician to change the properties of the light so it can focus in on different particles as is possible with a microscope.
While any real-world device is surely years away, the University of Michigan sees enough potential in the technology to have gone ahead and patented it.
Dexter Johnson is a contributing editor at IEEE Spectrum, with a focus on nanotechnology.
