Yes. This is one of the principle advantages of AFM, that it can be used in vacuum, in air, or in liquid. A liquid cell is USUALLY required. Top-down AFMs, for example, don’t really need one, it's sometimes possible to just put a drop of water on your sample, and scan in that. Usually water, or buffer are used but organic liquids are also possible, as long as they don’t damage the liquid cell, and can be held on the sample.