Figure 3.

Channel structures for every stage. (a) Spiral channel with trapezoidal cross-section for the first stage. (b) A square serpentine channel ($W\times H\times L_u$: $200\mu \text{m}\times 50\mu \text{m}\times 900\mu \text{m}$, and the number of units is 9) for the second stage. (c) A square serpentine channel ($W\times H\times L_u$: $150\mu \text{m}\times 50\mu \text{m}\times 600\mu \text{m}$, and the number of units is 11) for the second stage. (d) 3D-stacked multistage chip (area: $2.3\text{\hspace{0.17em}cm}\times 3.5\text{\hspace{0.17em}cm}$).