A profile shaping and surface finishing process of micro electrochemical machining for microstructures on microfluidic chip molds

In the lithography-based fabrication process of microstructures on microfluidic chip molds, the shortcoming of limited substrate materials seriously shortens the service lifetime of the mold. This research focuses on a profile shaping and surface finishing process of micro electrochemical machining (ECM) for microstructures with targeted dimensional and geometrical characteristics on the mold steel S136H. The effects of parameters on the material removal region and single-layer depth are firstly investigated. The sidewall taper of the machined groove increases with the machining voltage and decreases with the scanning velocity. Besides, the bottom surface quality is improved with increasing path spans. Then, the mathematical models of the material removal region and single-layer depth are analyzed, which are regarded as guidance for path planning and parameter optimization. In ECM experiments, a relatively higher machining voltage (20 V) is utilized to rapidly machine basic profiles of the designed flow resistor in the profiles shaping procedure. Sloping sidewalls and rough surfaces are finished by using a lower machining voltage (14 V) and a higher scanning velocity (500 μm s⁻¹) in the surface finishing procedure. As a result, the specially designed flow resistor with a dimensional deviation < 10 μm, and surface roughness R_a < 500 nm is obtained. The proposed ECM process is proved to machine microstructures with high precision and curve profiles on the mold steel.