Pneumatic pumps and Applications

This application note delves into the essentials of pneumatic pumps and their pivotal role in pressure-driven flow control systems. It highlights the advantages of proprietary piezoelectric regulation technology in enhancing the responsiveness and accuracy of these systems. Additionally, the document showcases the broad application spectrum of pressure-driven flow control in various industrial and research contexts.

Understanding pneumatic pumps is fundamental to grasping how pneumatics, a technology that leverages compressed gases to generate mechanical forces, operates. Pneumatic pumps use these mechanical forces to move fluids within microfluidic channels.

Unlike hydraulic pumps, which use fluids, pneumatic pumps employ air to exert mechanical forces, achieving similar outcomes with high power levels. This capability underscores the efficiency and versatility of pneumatic pumps in manipulating fluids, emphasizing their critical role in microfluidic flow control.

Basic principle of Pneumatic Pumps

The basic principle of a pneumatic pump is focused on the use of pressurized gas or air to move media. When pneumatic pumps are utilized for industrial applications, it involves the use of compressed inert gases or compressed air. 

These pumps utilize a double piston system. One of these pistons has a much smaller diameter than the other, and they are separated by an airtight chamber filled with a liquid or a compressed gas.

The compressed gas applies an external pressure on the larger diameter piston, which then applies pressure on the chamber of gas or liquid in the intermediate chamber. The smaller piston, thus receives a much more amplified level of force which in turn translates into powerful mechanical action.

Types of pneumatic pumps

Pneumatic pumps, recognized for their role as positive displacement pumps, operate as double-acting mechanisms without a return spring. They can utilize a variety of pressurized gases or fluids to function. Among the diverse types of pneumatic pumps, the following are notably prevalent in industrial settings:

• Pneumatic Diaphragm Pumps (Piston and Plunger Types): These pumps employ a plunger or piston mechanism to propel media through a cylindrical chamber, driven by pneumatic, electric, hydraulic, or steam power.
• Pneumatic Liquid Pumps: Specifically designed for the exclusive purpose of transporting liquids.
• Pneumatic Refrigerant Pumps: Primarily used for refrigerant transportation, these are typically two-stage pumps.
• Pneumatic Test Pumps: Engineered to evaluate the potential performance of a specific pneumatic system.

Leveraging the foundational principles of pneumatic pumps, Elveflow has pioneered the development of pressure-driven flow controllers. These devices ensure consistent and precise control of fluid flow across a variety of systems.

Elveflow’s innovation in pressure-driven flow control incorporates proprietary piezoelectric technology, enhancing the integration potential for a wide array of industrial applications—from droplet generation to sensor calibration. This technological advancement enables the pressure-driven flow controller to achieve unparalleled accuracy and responsiveness in flow regulation, setting new standards for efficiency and reliability in fluid dynamics.

Pressure driven flow control : Working Principle

A pressure controller initially pressurizes a container, whether it be an Eppendorf tube, Falcon tube, or a simple bottle holding the sample. This action leads to a smooth and almost instantaneous injection of the sample into a microfluidic chip. As illustrated in Figure 2, the reservoir is pressurized, the gas pushes on the liquid surface, hence the fluid flows in the microfluidic tubing and through the outlet. This process enables precise manipulation of the fluid’s flow out of the container by adjusting the input gas pressure. Integrating our pressure controller with a flow sensor allows for exceptionally accurate and responsive control over the fluid flow, ensuring precise and efficient operation within the microfluidic system.

When a flow rate value is set in the Elveflow Software Interface (ESI), the pressure controller automatically adjusts the pressure to reach the requested value thanks to a customizable PID feedback loop. The piezoelectric pressure regulation enables the Elveflow’s systems to handle flows with a stability of 0.005% and a responsiveness at 10 ms. The pressure driven flow control technology is also particularly interesting to handle various volumes of liquids, from µL to L.

Applications for pressure driven flow control

Pressure-driven flow control is versatile, finding utility across various scientific disciplines such as physics, chemistry, and biology. Our website features detailed discussions on its key industrial uses, including:

• Droplet Generation: Precision control for creating uniform droplets in microfluidic experiments.
• ALGINATE BEAD GENERATION: Facilitating the production of alginate beads for encapsulation and delivery systems.
• EMULSION STABILITY STUDIES: Essential for analyzing the stability of emulsions in cosmetic, food, and pharmaceutical products.
• PERFUSION IN DYNAMIC CELL CULTURE: Providing controlled flow conditions for cell culture experiments, simulating physiological conditions.

While traditional pneumatic pumps offer cost-effectiveness and have been utilized extensively, their performance limitations in terms of response time, accuracy, and pulse control become apparent in complex setups or when precise control is essential, as often encountered in microfluidics.

The adoption of pressure-driven flow control systems is on the rise, particularly for microfluidic applications where their performance—characterized by enhanced responsiveness, stability, and reproducibility—aligns with user expectations. The integration of piezoelectric regulation technology further complements these systems, ensuring they are suited for the vast majority of microfluidic applications.

How to implement pressure driven flow control?

Pressure driven flow control proves to be one of the best pneumatic pump systems for various reasons. It allows pulseless flow with a sub-second response time. It consists in using a gas input pressure within a hermetic liquid tank, in order to flow liquid from the tank to your microfluidic device.

This technology ensures fine handling of large fluid volumes (several liters) and allowing long-term experiments. The fast responsiveness and high stability of pressure-driven flow control offer critical features compared to peristaltic pumps for several applications from droplet generation, flow focusing, flow chemistry or synthesis.

Figure 3 is a schematic representation showing the OB1 pressure controller from Elveflow. It is connected to the monitoring software, microfluidic device/chip and the sample.

To know more about the capabilities of pressure driven flow control, and how to implement it in your current setup, reach out our microfluidics experts here!

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