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Related Concept Videos

Viscosity01:17

Viscosity

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When water is poured into a glass, it falls freely and quickly, whereas if honey or maple syrup is poured over a pancake, it flows slowly and sticks to the surface of the container. This difference in the flow of different kinds of liquids arises due to the fluid friction between the liquid layers and the liquid and the surrounding material. This property of fluids is called fluid viscosity. In this example, water has a lower viscosity than honey and maple syrup.
The SI unit of viscosity is...
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Surface Tension, Capillary Action, and Viscosity02:57

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Surface Tension
The various IMFs between identical molecules of a substance are examples of cohesive forces. The molecules within a liquid are surrounded by other molecules and are attracted equally in all directions by the cohesive forces within the liquid. However, the molecules on the surface of a liquid are attracted only by about one-half as many molecules. Because of the unbalanced molecular attractions on the surface molecules, liquids contract to form a shape that minimizes the number...
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Viscosity of Fluid01:19

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Viscosity measures the resistance a fluid offers to flow and deformation. It results from internal friction between layers of fluid moving relative to one another. Dynamic viscosity, denoted by the Greek letter mu (μ), quantifies the force needed to move one fluid layer over another. For Newtonian fluids like water and air, the relationship between the shearing stress and the rate of shearing strain is linear, meaning their viscosity remains constant regardless of the applied stress.
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Energy Line and Hydraulic Gradient Line01:27

Energy Line and Hydraulic Gradient Line

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Based on Bernoulli's equation, the energy line (EL) and hydraulic grade line (HGL) provide graphical representations of energy distribution in a fluid flow system. For steady, incompressible, inviscid flows, Bernoulli's equation is expressed as:
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Gradient and Del Operator01:14

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In mathematics and physics, the gradient and del operator are fundamental concepts used to describe the behavior of functions and fields in space. The gradient is a mathematical operator that gives both the magnitude and direction of the maximum spatial rate of change. Consider a person standing on a mountain. The slope of the mountain at any given point is not defined unless it is quantified in a particular direction. For this reason, a "directional derivative" is defined, which is a vector...
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Related Experiment Video

Updated: Feb 9, 2026

Dynamic Navigation in Endodontics: Guided Access Cavity Preparation by Means of a Miniaturized Navigation System
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Viscotaxis: Microswimmer Navigation in Viscosity Gradients.

Benno Liebchen1, Paul Monderkamp1, Borge Ten Hagen2

  • 1Institut für Theoretische Physik II: Weiche Materie, Heinrich-Heine-Universität Düsseldorf, D-40225 Düsseldorf, Germany.

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Summary

Microorganisms use viscotaxis to navigate towards favorable viscosity. This study reveals that specific body shapes create viscotaxis by generating asymmetric viscous forces, aiding survival and potential synthetic applications.

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Area of Science:

  • Microbiology
  • Biophysics
  • Fluid Dynamics

Background:

  • Microorganism survival, including Leptospira and Spiroplasma bacteria, is linked to navigating viscosity gradients.
  • Viscotaxis, the ability to move towards favorable viscosity, is observed in bacteria, but its mechanism is not fully understood.

Purpose of the Study:

  • To develop a theoretical framework for studying viscotaxis in microswimmers within slowly varying viscosity fields.
  • To elucidate the physical mechanisms underlying bacterial viscotaxis and explore its functional significance.

Main Methods:

  • Theoretical modeling of self-propelled swimmers in viscosity fields.
  • Analysis of viscous forces and their asymmetry based on microswimmer body shape.
  • Classification of microswimmers based on their viscotactic potential.

Main Results:

  • Suitable microswimmer body shapes can induce viscotaxis through systematic asymmetry in viscous forces.
  • Dynamic body shape changes in Spiroplasma and Leptospira may prevent migration to unfavorable low-viscosity environments.
  • The study provides a method to classify microswimmers by their viscotaxis capabilities.

Conclusions:

  • Microswimmer body shape is a key factor in generating viscotaxis.
  • Understanding viscotaxis mechanisms can explain microbial survival strategies and inform the design of synthetic microswimmers.
  • This framework can guide the development of targeted drug delivery systems using viscosity-guided microswimmers.