how do you define those two terms?
Let us try to get some definitions for:
aware
sentient
conscious
I'd think you could use the term aware even for a vacuum cleaner that
avoided obstacles. It is aware of its environment in that it senses
it, and reacts to it. Rocks don't appear to be aware.
My Oxford defines sentient as having the power to perceive via the
senses. This suggest only animals could be sentient. Perception by
other means does not count.
Conscious implies aware. It also implies an internal experience.
Perhaps it implies pain and pleasure. If something is not conscious,
it there is much less reason to avoid "hurting" it.
I know from having undergone anaesthesia that the experience
disappears when I go unconscious. It is not like sleep. Consciousness
seems to be associated with a certain degree of brain activity.
We might not be able to measure consciousness directly, but we can
measure brain activity.
We can only guess if that same degree of activity also indicates
consciousness in other species. It may require a lower or higher
amount for other brain designs.
You could find out with human experiments to anaesthetize only parts
of the brain, and see if even a small amount of the brain awake causes
consciousness, or if you need the whole thing functioning.
Part of the catch is, a human could be awake, but unconscious in the
sense of having no internal experience, and protest they were
conscious. We would never know they were "lying". They might not be
lying, just acting normally.
We need an indicator that tracks the subjective measure of just how
rich an internal experience you are having.
You then measure that indicator in other species, and use that to
decide if they are likely conscious, not your gut feelings.