Miniature landscape of channels illuminated by infrared light.

Miniature Flows, Major Impact: How Tiny Channels are Revolutionizing Tech

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Kai Mendoza in Tech & Innovation August 2025 • 4 min read.

"Unlocking the secrets of slug-bubble regimes in microchannels with infrared sensors could transform micro-thrusters and more."


In industries ranging from nuclear reactors to micro-chemical propulsion systems, the behavior of gas-liquid two-phase flow in capillary systems is critical. Understanding the liquid film thickness in different flow regimes, especially slug and bubble flows, is essential for optimizing system performance. Imagine designing a micro-thruster for a satellite – precise control over the propellant mixture is key to generating the exact thrust needed.

Traditional methods for studying these flows can be complex and intrusive. However, recent research has explored the use of infrared (IR) sensors as a non-invasive tool to characterize these flow regimes. This approach offers a way to 'see' inside these tiny channels and understand how the fluids are behaving without disturbing them.

This article delves into a study that uses an IR sensor to investigate slug-bubble train flow (alternating slugs of liquid and bubbles of gas) inside a small square channel. We'll explore how the sensor works, what the researchers discovered, and the potential implications of this technology for various fields.

Decoding Slug-Bubble Flow with Infrared Sensors: How Does it Work?

Miniature landscape of channels illuminated by infrared light.

The research focuses on experimentally and numerically investigating the behavior of an infrared sensor during two-phase flow of a slug-bubble train. The researchers used a square channel with sides of 2 mm and a thickness of 0.5 mm, made of borosilicate glass, to observe the flow. An IR transceiver unit, consisting of an IR transmitter and a photodiode receiver, was positioned perpendicular to the channel.

The IR transmitter emits infrared light, which then passes through the channel. As the slug-bubble train flows through, the different refractive indices of the air bubbles and water slugs cause the light to refract (bend) and scatter. The photodiode receiver measures the amount of light that makes it through the channel. The changes in the received light intensity correspond to the passing of slugs and bubbles, providing information about the flow regime.

  • The Setup: A mini-channel made of borosilicate glass, an IR transmitter, and a receiver.
  • The Process: Infrared light is sent through the channel, and the sensor measures the changes in light intensity.
  • The Data: These light variations are then translated into information about the flow of liquid and gas.
To complement the experimental work, the researchers also developed a numerical model using COMSOL Multiphysics. This model simulates the behavior of the IR rays as they pass through the channel and interact with the different phases (air and water). By comparing the experimental data with the numerical simulations, the researchers could validate their findings and gain a deeper understanding of the underlying physics.

The Future of Tiny Flows: Promising Applications and Beyond

The study successfully demonstrated the use of an IR sensor for characterizing slug-bubble train flow in a mini-channel. The experimental and numerical results showed good agreement, confirming the viability of this approach. This opens up exciting possibilities for various applications.

One key area is the development of micro-thrusters for nano-satellites. Precise control over propellant flow is crucial for these devices, and IR sensors could provide the necessary feedback for optimizing thrust. Furthermore, this technology could be applied in microreactors, lab-on-a-chip devices, and other microfluidic systems where understanding and controlling fluid flow is paramount.

While this research represents a significant step forward, there are still avenues to explore. Future work could focus on analyzing the effects of varying liquid film thickness, different flow shapes, and optimizing the IR transceiver design. With further development, this technology has the potential to revolutionize how we study and control fluids at the microscale.

About this Article -

This article was crafted using a human-AI hybrid and collaborative approach. AI assisted our team with initial drafting, research insights, identifying key questions, and image generation. Our human editors guided topic selection, defined the angle, structured the content, ensured factual accuracy and relevance, refined the tone, and conducted thorough editing to deliver helpful, high-quality information.See our About page for more information.

This article is based on research published under:

DOI-LINK: 10.1051/matecconf/201817201002, Alternate LINK

Title: Slug-Bubble Regime Identification In A Square Channel Using A Ir Sensor

Subject: General Medicine

Journal: MATEC Web of Conferences

Publisher: EDP Sciences

Authors: S Aafrin Sulthana., T Marieswaran., N Braghadesh., N Mithran., M Venkatesan.

Published: 2018-01-01

Everything You Need To Know

1

How does the infrared (IR) sensor work to characterize slug-bubble train flow?

The research uses an infrared (IR) sensor to study slug-bubble train flow in a mini-channel made of borosilicate glass. The IR transmitter emits infrared light through the channel, and the photodiode receiver measures the light intensity. Changes in light intensity correspond to the passing of liquid slugs and air bubbles, providing data about the flow regime. This non-invasive method avoids disturbing the flow, unlike traditional techniques.

2

What specific materials and equipment were used in the experiment to study slug-bubble train flow?

The researchers use a square channel with sides of 2 mm and a thickness of 0.5 mm, made of borosilicate glass, along with an IR transceiver unit. The unit consists of an IR transmitter and a photodiode receiver. The borosilicate glass allows for optical transparency, facilitating the passage of infrared light. COMSOL Multiphysics is also used for numerical modeling to simulate and validate the experimental results. The IR transmitter is positioned perpendicular to the channel.

3

What are the potential applications of using an IR sensor to characterize slug-bubble train flow in mini-channels?

The use of an IR sensor to characterize slug-bubble train flow opens up exciting possibilities for applications such as micro-thrusters, medical devices, and micro-chemical propulsion systems. Precise control over propellant mixtures, understanding liquid film thickness, and optimizing system performance are all enhanced by this technology. This approach allows for non-intrusive real-time monitoring and control, leading to more efficient and reliable systems.

4

Why did the research focus specifically on slug-bubble train flow?

The study focused on slug-bubble train flow (alternating slugs of liquid and bubbles of gas) because this flow regime is commonly encountered in various industrial applications, including nuclear reactors and micro-chemical propulsion systems. Understanding the dynamics of liquid film thickness and interfacial behavior in slug and bubble flows is crucial for optimizing the design and performance of these systems. The slug-bubble flow is very useful to predict behaviour in similar flow systems.

5

How was COMSOL Multiphysics used in conjunction with the IR sensor to validate the experimental results of the study?

The study uses COMSOL Multiphysics to create a numerical model that simulates the behavior of IR rays as they interact with air and water within the channel. By comparing the numerical simulations with the experimental data obtained from the IR sensor, researchers can validate their findings and gain a deeper understanding of the underlying physics governing the slug-bubble train flow. This combined approach enhances the reliability and accuracy of the results.

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