The new low shear viscosimeter LS300 for determination of viscosities of Newtonian and non-Newtonian fluids

Abstract

Abstract. The low shear viscometer LS300 permits measurements of viscosity with the same precision of the LS30 but is now fully controlled by the windows based software. That allows to determine viscosity at several shear rates and to establish flow curves enabling determination of the viscosity of non-Newtonian fluids. The viscosity of whole blood of ten adults was determined via flow curves approximated by Casson. The sensitivity of the LS300 was evaluated by determining the viscosity of water at rising temperatures and by establishing flow curves of ten specimen of the same blood sample. The low shear viscosimeters LS30/LS40 and with its latest development, the LS300 is sought-after in mineral oil industry, the cosmetic and food industry and in hemorheology, too. The technique of these devices based on the Couette principle ( Fig. 1) was described as golden standard technique (Pop et al. 2004) and most useful (Ernst et al. 1985) for determination of blood viscosity at single shear rates for the preceding models of the LS300. The new LS300 (KSPV-4, Rheomed GmbH, Aachen, Germany) is now fully controlled by the LS300 software and enables the operator to establish flow curves. Shear rate and viscosity are directly related to the properties of the fluid. Non-Newtonian fluids are governed by a non-linear relationship between shear stress and shear rate, whereas the viscosity of Newtonian fluids is independent from shear rate (Fig. 2), as indicated by the linear relation between shear rate and shear stress (Papaioannou et al. 2005). These flow curves can be approximated by mathematical models, which allow calculating the viscosity of a non-Newtonian fluid like whole blood (Shi et al. 1996;Baskurt et al. 2003;Marcinkowska-Gapinska et al. 2007).The LS300 (proRheo GmbH, Althengstett, Germany) is a rotational rheometer based on the Couette principle ( Fig. 1), equipped with a rotating measuring cup and a fixed measuring element. Thus, the measurements are not influenced by the Taylor vortex. The measuring principle is the same as the LS30 previously described (Aarts et al. 1984). The material number of the cup and the bob is steel (EN 1.4571).The radius of the measuring cup is 6 mm, the radius of the bob is 5.5 mm and the length of the bob is 8 mm. The sample volume was 0.9 ml. The bob was always covered with the tested sample. The software LS300 regulates the rotation count of the measuring cup. The number of measuring points at several shear rates and time may be selected as desired. The thermostat of the LS300 works with cryoregulation; its accuracy is ±0.1°C. The new technology of LS300 permits determination of shear forces at multiple shear rates during a single measuring run, over a wide range of shear rates from 0.018 to 125 s −1 (in steps of 0.01 s −1 ). By graphic presentation of shear rate versus shear stress one obtains data points which, when connected to each other, yield a flow curve (Fig. 3). The viscosity of non-Newtonian fluids can be determined by approximation of these flow curves with mathematical mo...

On the Effects of Reactive Oxygen Species and Nitric Oxide on Red Blood Cell Deformability

“…Whole blood viscosity measurements were conducted using the LS300 viscometer (proRheo, Althengstett, Germany) as described by Ruef et al ( 2014 ). Briefly 1 mL of treated whole blood suspension was measured at 37°C for a range of different shear rates (0.5–150 1/s).…”