Micro check valves having a free-floating member for controlling flow of fluid in microfluidic and biomedical applications and methods of fabrication. A micro check valve includes a valve seat, a valve cap that contacts the valve seat and an untethered floating member that can move between the valve seat and the valve cap. Certain micro check valves have zero cracking pressure and no reverse leakage. Certain other valves may be configured to permit flow of fluid within a pressure range. The floating member can be solid or define an orifice, and the valve seat can have one or two levels. Valves can be configured to allow fluid to flow when the floating member is pushed by fluid against the valve cap or against the valve seat. The valve seat may be silicon or another material that is compatible with micromachining processes, and the valve cap and the floating member may be a polymer such as Parylene.