We proposed a three-inlet planar mixing geometry, named cascaded splitting and recombination (C-SAR). The C-SAR mixer works in a wide range of Reynolds number (34.6-150) with 90% mixing efficiency; the mixing time is as short as sub-milliseconds and sample consumption is as low as a few microliters per second. The asymmetric arranged triangular baffles in the mixing region introduce C-SAR, which transports the central fluid toward channel walls further than symmetric splitting and recombination (S-SAR), resulting in more effective mixing with fluids from side inlets; meanwhile, corner vortices and Dean's vortices are generated when fluids pass through sharp bends formed by triangular baffles or channel edge with high speed, which creates chaotic advection and enhances mixing. Therefore, C-SAR greatly improves mixing efficiency compared with S-SAR. This easily fabricated C-SAR rapid mixer is an attractive tool to study biomacromolecular dynamics. (C) 2018 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.