A new technique for continuously monitoring both the size and optical properties of individual airborne particles could offer a better way to monitor air pollution. It is especially promising for analyzing fine particulate matter measuring less than 2.5 microns (PM2.5), which can reach deep into the lungs and cause health problems.
[...] For the new analysis approach, airborne particles are trapped inside a laser beam by optical forces and propelled forwards by radiation pressure. The trapping force is strong enough to overcome the gravitational force acting on very small particles such as PM2.5 and automatically aligns the particles with a hollow-core photonic crystal fiber. These special fibers feature a central core that is hollow and surrounded by a glass microstructure that confines light inside the fiber.
Once aligned, the laser light propels the particle into the fiber, causing the laser light inside the fiber to scatter and createe a detectable reduction in the fiber transmission. The researchers developed a new signal processing algorithm to retrieve useful information from the particle-scattering data in real-time. After detection, the particle simply ejects from the fiber without degrading the device.
"The transmission signal from the fiber also lets us measure time-of-flight, which is the time the particle takes to travel through the fiber," said Abhinav Sharma, the doctoral student working on this project. "The drop in fiber transmission together with the time-of-flight information allow us to unambiguously calculate the particle size and refractive index. The refractive index can assist in identifying the particle material because this optical property is already known for most common pollutants."
Journal Reference: Abhinav Sharma, Shangran Xie, Richard Zeltner, Philip St.J. Russell. On-the-fly particle metrology in hollow-core photonic crystal fibre. Optics Express, 2019; 27 (24): 34496 DOI: 10.1364/OE.27.034496
(Score: 4, Insightful) by JoeMerchant on Friday November 15 2019, @04:10PM (2 children)
What we lack is the political will to impose even an approximation of the true costs of pollution on the polluters.
🌻🌻 [google.com]
(Score: 5, Insightful) by Thexalon on Friday November 15 2019, @05:52PM (1 child)
Until those danged environmentalist types start being able to bribe congresscritters and presidents the way most industries can, or we somehow manage to make or keep holders of political office non-corrupt, I'm not going to be optimistic.
Especially since the current administration wants to make it harder for the EPA to perform research on the effects of pollution on human health [rollcall.com].
The only thing that stops a bad guy with a compiler is a good guy with a compiler.
(Score: 2) by JoeMerchant on Friday November 15 2019, @09:26PM
There's a very old philosophical concept 2-3 millennia at least, billions of believers - many actual adherents, it goes something like this (in any one of a thousand languages):
Do not do to others what you would not want them to do to you.
With the coming robot revolution and the attendant hordes of idle unemployed, I would think that closer scrutiny of our elected officials' activity would be a worthy use of many people's time. The higher the office, the more detailed the scrutiny, and when a super majority of common voters believe that an elected official has violated the above principle, the penalty should be (in direct violation of that most Christian of themes: turn the other cheek) to visit upon the elected official whatever unpleasantry they have been shown to visit upon their constituency, or they may excuse themselves from office, permanently. We've put up with too much of this [kym-cdn.com] for one reality.
🌻🌻 [google.com]
(Score: 2) by Coward, Anonymous on Friday November 15 2019, @05:11PM (1 child)
The article (open access!) says
But the light is strong (3W laser focused into an 18 micron fiber core). If it vaporizes the particles, they will foul up the fiber.
(Score: 0) by Anonymous Coward on Friday November 15 2019, @05:16PM
Wonder if it will clog if there is a power interruption and the laser is turned off for awhile?
(Score: 0) by Anonymous Coward on Friday November 15 2019, @05:13PM (1 child)
> After detection, the particle simply ejects from the fiber without degrading the device.
This might work most of the time, but some of those particles could be sticky. Maybe they also envision some kind of trap upsteam of the hollow fiber optic to keep it clean. Pretty hard to imagine a way to clean out the inside of such a thin tube, Q-tips don't come that small.
(Score: 2) by JoeMerchant on Friday November 15 2019, @05:27PM
I imagine the tubes are also rather cheap to make, and can be replaced periodically in a practical device.
🌻🌻 [google.com]
(Score: 2) by bd on Saturday November 16 2019, @12:20PM
They make it sound as if real-time, or near real-time particulate matter monitoring is somehow difficult and error-prone (it has been done since the 1980's), in order to make their overcomplicated, most likely overexpensive setup sound reasonable.
Also, it is not practical at all:
They prevent clogging of the fiber using a filter. Filters introduce large errors. If you are in a place where there is an actual health concern, this filter will also clog up.
If there is mist in the air, the filter will get wet. This will affect the size of particles it catches.