Universal Stokes’s nanomechanical viscometer

Abstract

Although, many conventional approaches have been used to measure viscosity of fluids, most methods do not allow non-contact, rapid measurements on small sample volume and have universal applicability to all fluids. Here, we demonstrate a simple yet universal viscometer, as proposed by Stokes more than a century ago, exploiting damping of capillary waves generated electrically and probed optically with sub-nanoscale precision. Using a low electric field local actuation of fluids we generate quasi-monochromatic propagating capillary waves and employ a pair of single-lens based compact interferometers to measure attenuation of capillary waves in real-time. Our setup allows rapid measurement of viscosity of a wide variety of polar, non-polar, transparent, opaque, thin or thick fluids having viscosity values varying over four orders of magnitude from $$10^{0}{-}10^{4}~\text{mPa} \, \text{s}$$ 10 0 - 10 4 mPa s . Furthermore, we discuss two additional damping mechanisms for nanomechanical capillary waves caused by bottom friction and top nano-layer appearing in micro-litre droplets. Such self-stabilized droplets when coupled with precision interferometers form interesting microscopic platform for picomechanical optofluidics for fundamental, industrial and medical applications.

Miniature viscometer incorporating GaN optical devices with an ultrawide measurement range

“…Their implementation relies heavily on the assembly of external light-emitting and detecting units as well as the optical elements used for light coupling. Although noncontact measurements based on optical tweezers and interferometric probes make accurate viscosity measurements possible with low sample consumption [25][26][27] , they often involve complex and expensive microscopic setups. The GaN semiconductor and its alloys have been considered an ideal platform for developing light-emitting devices because of their high efficiency, long lifespan, and high physical stability 28,29 .…”

Physical Properties and Molecular Interactions Applied to Food Processing and Formulation

“…In addition, Stokes viscometers have been widely used in quality control. This last type of equipment is based on the measurement of the time a sphere submerged in fluid takes to pass through two points under the action of gravity at terminal velocity [96,97].…”