na-adjective
intentional; deliberate; contrived; artificial
Describes actions, behavior, or expressions that are not natural or spontaneous but done with a specific purpose, often with a negative connotation of being forced or unnatural.
彼の笑顔は作為的に見えた。
His smile looked contrived.
その発言は作為的なものだった
That remark was intentional.
わざと is a casual adverb meaning 'on purpose', often used for minor or everyday actions, whereas 作為的 is a more formal adjectival noun describing the quality of being contrived.
From 作為 (sakui, 'artificiality; intentional act') + 的 (-teki, '-like, -ish'). 作為 is composed of 作 (saku, 'make') and 為 (i, 'do'), referring to something done by human design rather than naturally occurring.