I wanted to know if air particles can cross through (transverse direction) an ultrasound wave or they will start to oscillate in the direction of wave propagation (longitudinal) when they get in contact with the wave and get trapped inside the wave. Can I create a zone where particles cannot cross over to the other side of the ultrasound wave ?
If you consider linear regimes, then the ultrasonic wave should act as yet another "normal" sound wave. This means that the movement of the "particles" will move in a way dictated by the superposition of the travelling ("main") wave and the ultrasonic wave. Linearity applies here too so this shouldn't be different from two sound waves travelling in perpendicular directions meeting at a point in space.
Now, regarding creating a shaded area, I am not sure this can be achieved in the way you think of it. Maybe creating a pressure null on a specific direction or point in space could be a more appropriate approach, but this again depends on the application. I believe that if you don't provide more info on the specifics of the application we won't be able to provide much more help.