It is kind of an onomatopoeia !
Probably the {}{} : zigzagged in order to imply the "lightning"-like effect of the beam from the eyes of the robot.
I guess the sound effect is similar to "beep"(high pitched sound) in English.
Does it seem to appropriate to your scene? () is used when you are surprised. But this time, the robot seems to be attacking, so it does not seem to be appropriate.