Contact-free determination of viscosity in multiple parallel samples

Abstract

Viscosity is an inherent characteristic of fluids and is therefore an important parameter in many different processes. Current methods to measure viscosity involve direct contact with the liquid sample, which is often undesirable. Here we present a simple, precise and robust contact-free method to determine viscosity, using a single drive motor, inexpensive components and disposable sample vessels. The measurement principle involves the detection of viscosity-dependent angular positions in a rotating liquid relative to the direction of centrifugal acceleration in an orbitally shaken vessel. The signal can be detected using different optical methods, as shown here using fluorescence and transmitted light. The sensitivity of the system can be adjusted over a wide range by varying the sample volume or the shaking diameter, and multiple samples can be analysed in parallel. This novel viscometer is also applicable to characterize non-Newtonian shear rate-dependent fluids.

Reassessing the out‐of‐phase phenomenon in shake flasks by evaluating the angle‐dependent liquid distribution relative to the direction of the centrifugal acceleration

“…As discussed earlier for Figures and a,b, the angular position of LB increases with viscosity. Sieben et al () describe how to use the shift of the angular position of the leading edge to measure viscosity.…”

“…Therefore, to date, two independent methods have proven the negative impact of the OP phenomenon. Sieben, Hanke, and Büchs (2019) used two different optical methods to evaluate the position of the rotating bulk liquid in shake flasks relative to the direction of the centrifugal acceleration. It was discovered that the position of the bulk liquid turns into the direction of the liquid rotation with increasing viscosity.…”

Combined dissolved oxygen tension and online viscosity measurements in shake flask cultivations via infrared fluorescent oxygen‐sensitive nanoparticles

“…However, the above‐mentioned techniques are not applicable for viscous culture broths. Due to increased viscosities, the position of the bulk liquid relative to the direction of the centrifugal acceleration changes (Sieben, Hanke, & Büchs, ). A lag of up to 90° between rotating bulk liquid and the direction of the centrifugal acceleration may appear (Büchs, Maier, Milbradt, & Zoels, ).…”

“…Therefore, the DOT measurement is not performed at a constant position during the rotation of the shaker table but initiated in dependence of the position of the rotating bulk liquid. To detect the leading edge of the bulk liquid, a recently published optical technique described by Azizan and Büchs () and Sieben et al () is adopted. As extremely valuable “by‐product,” also the culture broth viscosity can be derived from the measured signals as described by Sieben et al ().…”

“…To detect the leading edge of the bulk liquid, a recently published optical technique described by Azizan and Büchs () and Sieben et al () is adopted. As extremely valuable “by‐product,” also the culture broth viscosity can be derived from the measured signals as described by Sieben et al (). The applicability is demonstrated for cultures of E. coli , Bacillus licheniformis , and Xanthomonas campestris .…”