An Efficient 3D-Printed Gravity Mixer for Lab-on-a-CD Applications.

We introduced a new, highly efficient, and uncomplicated mixing device for centrifugal microfluidic platforms, called the gravity mixer. The gravity mixer featured a slope channel that can precisely and sequentially control micro-volume liquids using centrifugal, capillary, and gravitational forces to achieve the desired mixing effect. By adjusting the angular velocity, micro-volumes of liquids in the slope channel of the gravity mixer could be precisely controlled across a wide range. We evaluated the change in mixing efficiency by varying the slope geometry, including the slope angle and the number of mixing cycles. Our study of gravity mixers with different slope angles revealed that the 80° angle gravity mixer achieved the best mixing efficiency, with a standard deviation of 2.39. Additionally, the mixing process in the gravity mixer is highly repeatable, achieving the desired mixing efficiency after only three cycles of operation. Our gravity mixer design and implementation can facilitate the development of more complex 3D-printed lab-on-chip devices.