Neutrally Buoyant Particles – What Are They, What Are They Used For, How to Use Them?

What are Neutrally Buoyant Particles?

Neutrally buoyant particles are particles that neither sink nor rise when placed in a fluid. They remain suspended at a fixed depth within the fluid, maintaining their position seemingly without the influence of gravity. Neutral-buoyancy is achieved when the density of the particles matches the density of the surrounding fluid exactly.

What are the Applications of Neutrally Buoyant Particles?

By carefully controlling the tracer particle’s density, researchers and engineers create conditions where the particles remain suspended and move with the flow, allowing for valuable insights into various fluid-related phenomena. This investigation is often called flow visualization or particle image velocimetry (PIV).

Neutrally buoyant particles have various applications across different fields, including:

1. Biological and Medical Sciences:
   • In biological research, neutrally buoyant particles can be used to simulate the behavior of cells or microorganisms in a fluid medium. This is particularly useful for studying the movement and interactions of microorganisms in aquatic environments or in vitro experiments.
2. Marine and Environmental Sciences:
   • In oceanography and limnology, neutrally buoyant particles can mimic the behavior of plankton or other suspended particles in water. This helps scientists understand how these particles are transported by ocean currents and turbulence.
3. Fluid Mechanics and Engineering:
   • Neutrally buoyant particles are used to investigate fluid flow patterns and turbulence in laboratory experiments. They can be seeded into a flow to visualize and analyze the motion of fluid, providing insights into the behavior of gases and liquids.
4. Aerospace Engineering:
   • In wind tunnel testing, neutrally buoyant particles can be employed to simulate the behavior of airborne particles, such as dust or ice crystals, in order to assess their impact on aircraft performance and safety.
5. Chemical Engineering:
   • In chemical processes, neutrally buoyant particles can serve as tracers to monitor the movement and mixing of fluids within reactors and pipelines, aiding in process optimization.
6. Oil and Gas Industry:
   • In the oil and gas sector, neutrally buoyant particles can be used in drilling fluid systems to study the behavior of drilling mud and additives under various conditions. This helps optimize drilling operations.
7. Underwater Robotics:
   • Neutrally buoyant particles can be used in underwater robotics and remotely operated vehicles (ROVs) as ballast materials to achieve stable buoyancy control.
8. Laboratory Calibration and Testing:
   • Neutrally buoyant particles can be used as calibration standards for particle sizing instruments and flow visualization techniques, ensuring accurate measurements and results.
9. Geological and Geological Engineering:
   • In geological studies, neutrally buoyant particles can be employed to simulate sediment transport and deposition in rivers and streams, helping researchers understand erosion and sedimentation processes.

How are Neutrally Buoyant Particles Manufactured?

Neutrally buoyant particles, also often called tracer particles or seed particles, are manufactured by using a unique formulation of materials and coatings that combine to create specific gravity virtually identical to that of the surrounding fluid.

How to Source Neutrally Buoyant Particles?

When sourcing neutrally-buoyant particles to suspend in a specific fluid, the first question is to know the density of the fluid precisely. The delta between the densities of the particle and of the fluid needs to be minimized. If there is any mismatch in density of tracer particles (seed particles) and the density of fluid the particles will not remain suspended.

A variety of neutrally-buoyant microspheres designed for use with a variety of fluids are currently offered by Cospheric LLC.

Brightly colored and fluorescent polymer microspheres are polyethylene based and specifically designed for use as precision flow tracers and seed particles for water flow visualization and particle image velocimetry (PIV) experiments.

Densities between 0.98g/cc and 1.45g/cc makes polyethylene based microspheres great seed particles or tracer particles for aqueous based applications.

Silver Coated Hollow Glass microspheres were specifically designed as tracer or seed particles for flow visualization and particle image velocimetry applications in biotechnology which often require a true particle density slightly higher or lower than what is possible with polyethylene tracer particles.

What makes fluorescent tracers and silver-coated tracers uniquely suitable as neutrally-buoyant particles for flow visualization applications is that they are highly visible in fluid flows and can be easily visualized with the help of light and lasers.

If you need help selecting the right tracer particle or neutrally-buoyant particle for your application, don’t hesitate to reach out to Cospheric Technical Support for a recommendation.