Slotted plate device to measure the yield stress of biofluids

The slotted plate device by Zhu et al. was redesigned to allow for the measurement of very low yield stress values that occur with complex biofluids. The newly built apparatus improves the force measurement with a balance of fine resolution and smooths the vertical motion via a lab jack. The slotted plate geometry was optimized to further reduce wall slip as well as pressure drag via computational fluid dynamics (CFD). To improve on the yield stress measurement accuracy, the new design has a large slot area ratio and a large number of slots, as well as sharp front and rear edges. Test results for a few structured fluids, including blood, are compared with yield stress values determined via a TA Instruments AR-2000 rheometer.