Barrier Eggman is the third sub-boss of Sonic & Knuckles, fought in Flying Battery Zone Act 2 before the Zone's main boss, the Hang Mobile.
Much like he did the last time Sonic wandered into his aerial fortress, Dr. Eggman slams on flickering forcefield barriers to lock the player into a chamber, and then opens fire with a roof-mounted laser. However, this iteration of Barrier Eggman involves no spiked platforms twirling about in the air; instead, the walls close in on the player every time the laser is fired, reducing the amount of room to maneuver in. Just like in Sonic 2, the player is able to hit the laser to make it flash, as long as they can jump high enough. However, there's no way to destroy it this way.
This sub-boss is eventually self-defeating; the player should dodge the laser for long enough and Eggman misfires, blowing up something important and causing the whole of the Flying Battery to rumble in a most disturbing manner. Chase the Doctor through the airship's collapsing superstructure to make it to the Hang Mobile.
As Hyper Sonic, the player can actually leap through the barrier if Hyper Sonic's double jump is timed right. The easiest way to do it is to double jump to the right when the laser shoots. If successful, the player cannot defeat Eggman right there, but they are able to enter the later part of the Act. The objects are glitched until the boss is defeated off-screen.