Table 2.

Active micromixers reported in recent five years.

Dimension	Structure	Characteristic	Re	Mixing Length (μm)	Mixing Efficiency	Reference
2D	Unbalanced collisions channel	Unbalanced three-split recombine sub-channels	30–80	8275	90% 3	[95] a
		Dislocation structure	<80	8000	85% 2	[96] c
	Embedded Barriers channel	Triangle baffle	1	6400	85.5% 3	[97] c
		Curved micromixers with cylindrical obstructions	0.1–60	8280	88% 3	[98] a
	Spiral	Single logarithmic spiral	67	12,000	86% 4	[99] c
		Double logarithmic spirals	50	5000	80% 3	[100] a
	Convergent–divergent channel	Sigma channel	0.91	8000	79.1% 3	[101] a
		Semi-elliptical walls	35.5	-	80% 2	[102] c
		Convergent–divergent walls	10–70	6720	90% 3	[103] a
		Ellipse-like micro-pillars	≤1	9000	80% 2	[104] c
		Reversed flow in square wave channel	≤0.1 or ≥10	3710	95% 2	[105] a
		Reversed flow in zigzag channel	≤0.5 or ≥5	-	93% 2	[106] a
3D	Chamber	Trapezoidal chambers	0.5–60	3870	80% 2	[107] a
		Trapezoidal-zigzag channels	0.1–0.9 or 20–80	3610	90% 3	[108] a
		Unbalanced split and cross-collision chambers	0.5–100	5000	80% 2	[109] c
		Circular mixing chambers	0.1	6400	88%3	[110] a
		Split and recombine chambers	1–100	-	90% 3	[111] c
	3D Spiral	Three dimensional spirals	40	2340	90% 1	[112] c
		Cross-linked dual helicals	0.003–30	320	99% 2	[113] a
		Tapered structures	50	10,500	90% 3	[114] c
	Overbridge	Overbridge-shaped channel	0.01–50	2000	90% 4	[115] c
		Tesla structures	0.1–100	10,700	94% 2	[116] c
		X-shape structures combined with H-shape structures	0.3–60	102,500	87.7% 3	[117] c
		X-shape structures combined with O-shape structures	0.3–60	102,500	72.9% 3	[117] c
		Serpentine crossing channels	0.2–10	7500	99% 3	[118] c

^a Research including only simulated results. ^b Research including only experimental results. ^c Research including both of simulated and experimental results. ¹ Mixing Index calculated based on Equation (1). ² Mixing Index calculated based on Equation (2). ³ Mixing Index calculated based on Equation (3). ⁴Mixing Index calculated based on Equation (4).