The proposed cylindrical magneto-hydrodynamic (MHD) micromixer developed in this study was a geometrically modified conventional T-micromixer combining the characteristics of passive and active micromixers. Characterization was achieved by observing the mixing efficiencies of NaCl solution (1% concentration) based on supplied electrical potential and inlet flow rates. The design mainly aimed to utilize the pumping capability of the magneto-hydrodynamic principle as a secondary element to give counter pumping energy towards inlet flows, such that perturbation of fluid increased mixing performance. NaCl solution was mixed by advection through the stretching and folding by micro-vortices generated in the mixing reservoir. The cylindrical MHD micromixer achieved its highest mixing index of 99.42% at Re = 40 with 3 V of direct-current potential (VDC) supplied to the electrodes. Mixing efficiency increased in a considerably similar and linear pattern for Re = 5, 10, 20, and 40 within the electrical potential range of 0.5 ≤ V ≤ 3.0. Control was gained by manipulating the external electrical potential source which only required a smaller capacity of direct-current voltage sources. Overall, the proposed cylindrical MHD micromixer, which emphasizes the use of inexpensive material and simple design, has been experimentally proven to be practical as compared to the passive and active micromixers found in the literature.

A two‐dimensonal Tesla micromixer is experimentally characterized at varying Reynolds numbers (Re) and valve stages with the aim to acquire sufficiently high mixing performance. To ease fabrication, a simplified Tesla valve design is adopted. Results show two distinctive regimes of low and high Re. In the low‐Re regime, a steady incremental mixing was observed as the fluid passes by each valve, whereas an enhanced mixing was identified right in the first valve in the high‐Re regime. This is predominantly due to the amplified opposing flow from the helix branch which promotes stronger chaotic advection in the main microchannel. Interestingly, the measured mixing performance was found comparable to that of three‐dimensional passive micromixers reported in the literature.

The pumping mechanism in multi‐inlet microfluidic channels usually requires multiple micropumps to be separately attached to each inlet. Unfortunately, this may create fluid leakage resulting from a considerably high internal pressure. To address this, a passive sub‐atmospheric pressure‐inducing micropump is proposed and its performance is characterized as a function of the flow rate and the gauge pressure. With this pump, a sufficiently high flow rate is generated, comparable to some active‐piezoelectric micropumps. The gauge pressure is exponentially descending with time and can be crudely classified into three regions of high, moderate, and slow pressure‐release times. Overall, the stabilized pressure is identified within 70 s < t ≤ 300 s for slow rate mixing while rapid mixing is applicable at t ≤ 70 s.

Paper-capillary micropumps are advantageous as they are small in size, cost-effective, and easily disposable. However, capillary-based micropumps fabricated using the photolithography technique prevent exchanging of the pumping element. The liquid movement in paper-based micropumps is also difficult to control and manipulate as compared to non-paper-based micropumps. Therefore, in this study, the performance of a multi-angle paper-based capillary micropump that utilizes both hydrostatic and paper-capillary effects with a detachable paper matrix is presented. The design offers enhanced and controllable flow rates based on paper matrix types and platform inclination angles. In addition, the paper matrix pumping element does not involve in the analytical processes but rather only for fluid driving. Standalone operation shows a working range of flow rate comparable to some purely capillary- and hydrostatic-based micropumps reported in the literature. The proposed micropump shows that the flow rate is linearly increasing based on the types of capillary papers and platform inclination angles, giving a flow rate range of 2.3 μL/s ≤ [Formula: see text]  ≤ 2.44 µL/s.