It says the probe itself is the size of a microchip. Let's be generous and suppose it's the size of a modern Intel x86 processor. How does it communicate with Earth? There has to be some kind of antenna dish; so OK, maybe the sail can serve dual functions. How does it do attitude adjustment?
Presumably some of this chip-sized probe is a sensor of some kind; perhaps a camera. Without a sensor, it's hard to see how one could think of it as a "probe" at all. Does this camera have a lens? How big? A lens the size of an Intel processor won't capture much light, and I'm not sure the bandwidth from Alpha Centauri is going to be good enough for digital imagery.
How is the probe's transmitter to be powered? A battery no larger than a microchip seems a little inadequate for communicating between Alpha Centauri and Earth.
OK, so the probe doesn't start transmitting until it can harvest energy from Alpha Centauri itself. But now it needs a solar panel! A solar panel up to the job simply can't be made the size of a microchip.
Maybe it's not supposed to send any data back at all; maybe it's just meant as a proof of concept. But even our best telescopes can't detect something 3m wide, in the region of Alpha Centauri. So the only concept this could ever prove is that you can accellerate something to c/5; there's no point in aiming it Alpha Centauri.
The article doesn't say how long these lasers are supposed to keep running; it seems unlikely they'll stay focused on the sail much past the orbit of Jupiter. I haven't tried to do the maths, but to accellerate something the size of an x86 to c/5, I imagine the lasers will have to run continuously for over a year; how much is that going to cost, for a probe that can't send back data?
Hmm - the article is bylined "Deborah Byrd". So I click on the byline, and get a photo and bio of astronomer Theresa Wiegert. Who is Deborah Byrd?
I've never heard of earthsky.org before, but my confidence in this publication is immediately diminished on my very first visit.