1 N is the force of Earth's gravity on a mass of about 102 g = (1⁄9.81 kg). On Earth's surface, a mass of 1 kg exerts a force of approximately 9.81 N [down] (or 1.0 kilogram-force; 1 kgf = 9.80665 N by definition).
From the article:
the researchers observed apparent thrusts of ~20 micro-Newton
So we're not talking much 'force' of acceleration here.................
If you look at current ion thruster technology you’ll find they produce anywhere from 20 to 250 milli-Newtons of thrust which is a bit higher than 20 micro-Newtons with efficiencies anywhere from 60 to 80 percent.
https://en.wikipedia.org/wiki/Ion_thruster