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Abstract: Inspired by the animal upper digestive tract, a unique soft-elastic reactor (SER) has recently been researched whose mixing phenomena should be further investigated. Numerical simulation is an excellent method with which to explore the phenomena in SERs for a large number of conditions. It may also offer insights into the ways of effective mixing in this kind of reactor. The mixing processes in 2D SERs driven by bio-inspired wavelike boundary motions are systematically compared in this work. The influences of several key factors (i.e. the aspect ratios of rectangular SERs, the wavenumbers of moving walls, and the location and size of baffles) on the mixing performance are investigated. It has been found that mixing efficiency is better at an aspect ratio close to 1.0. The influence of wavenumber on mixing is not monotonic. Increasing the wavenumber speeds up mixing in parallel boundary type motion, while it slows it down in symmetrical-contraction boundary type motion. Mounting baffles on the left and right sides of the vessel wall (i.e. on the moving boundaries) promotes mixing. Lower porosity (<0.4) of baffles benefits mixing. It has become clear that an efficient SER needs to be designed by considering not only its shape but also the wall moving mode. The work reported in this article has provided useful information on how it might be possible to improve SERs for industrial applications in future.