Solenoid valves are a common solution for fluid control. They are simple, affordable, easy to power, and widely used in many industrial applications. For basic open or close tasks, especially outside microfluidics, solenoid valves remain an effective and reliable option.
However, microfluidic systems place very different requirements on flow control, pressure stability, and internal volume. As soon as a microfluidic application involves multiple fluids, sensitive samples, precise flow rates, or automated sequences, the limits of solenoid valves quickly appear. What works well for simple liquid routing does not always scale to complex microfluidic devices.
This is why many engineers start looking for alternatives to solenoid valves, especially when designing advanced microfluidic systems. Rotary valves, motorized valves, and other microvalve technologies offer a different approach to fluid control, one that focuses on precision, efficiency, and reliability.
AMF’s On Off rotary valve was designed specifically for these situations. It is a 2-port rotary microfluidic valve based on a hard sealing architecture, optimized for very low internal volume, no dead volume, and stable long-term performance. Instead of multiplying solenoid valves, tubing, and fittings, a single rotary valve can be used as a controlled access point within a fluidic system.
In the following sections, we look at where solenoid valves reach their limits in microfluidic systems, how rotary valves address these constraints, and how to choose the right valve technology depending on the complexity of the application.
The goal is not to replace solenoid valves everywhere, but to help engineers choose the right valve technology based on the real constraints of their microfluidic application.
Solenoid valves are widely used as fluidic components because they are easy to integrate, electrically powered, and well suited for basic flow control. In their simplest form, a solenoid valve uses an electromagnetic coil to move a plunger or deform a membrane, opening or closing a fluid path when power is applied.
In most microfluidic systems, solenoid valves are used as direct acting valves. A common configuration is the 2/2 solenoid valve, which has one inlet and one outlet and simply switches between open and closed states. Another frequently used configuration is the 3/2 solenoid valve, which adds a third port, typically used to vent, redirect, or switch between two flow paths.
These valve types work very well for simple liquid handling tasks, especially when the objective is to start or stop flow with minimal control logic.
In microfluidic systems, however, flow control is rarely limited to a single on off action. Microfluidic devices often combine multiple components such as syringe pumps, pressure regulators, pressure controllers, reservoirs, and microfluidic chips. Together, these components must deliver stable pressure values, controlled flow rates, and repeatable timing across complex fluidic networks.
As soon as a microfluidic application involves:
the valve becomes a critical part of the system.
Solenoid valves were not designed to handle these constraints. Their internal structure often includes cavities, flexible membranes, or elastomeric seals. In microfluidic channels, these features introduce dead volume, uncontrolled volume displacement, and pressure fluctuations that directly affect flow stability.
For applications such as flow focusing, droplet generation, cell culture, or sample preparation, even small variations in pressure or internal volume can impact performance, repeatability, and data quality.
Another limitation appears when a microfluidic system must handle more than one fluid. In a solenoid based architecture, each fluid path typically requires its own valve. Whether using multiple 2/2 solenoid valves or combining several 3/2 valves, the system quickly grows in complexity.
As the number of reagents increases, the system rapidly accumulates:
This approach scales poorly. Switching between fluids becomes sequential and time consuming, cleaning cycles become longer, and the risk of cross contamination increases. For microfluidic applications using rare or expensive reagents, this can lead to significant sample loss and increased operating cost.
Solenoid valves interact directly with pressure control. In microfluidic systems driven by syringe pumps or pressure regulators, opening or closing a solenoid valve does not only stop or start the flow, it also changes the internal volume of the fluidic path.
This sudden volume change can generate pressure spikes and transient flow disturbances. In many industrial fluidic systems, these effects are acceptable. In microfluidic applications, however, they can significantly impact pressure stability and flow precision.
A common example is parasitic backflow. When a solenoid valve closes, the movement of the plunger or membrane can momentarily displace liquid upstream or downstream. In pressure driven microfluidic systems, this displacement can push fluid backward into connected channels or reservoirs. This effect is often small, but at microfluidic scale it becomes measurable and repeatable.
Parasitic backflow can lead to:
These effects are particularly problematic in applications requiring precise pressure control, such as flow focusing, droplet generation, or cell based microfluidic experiments.
Automation further amplifies these issues. As microfluidic systems become more automated, valves are actuated more frequently and in tighter sequences. Each actuation event introduces a small disturbance, and when multiple solenoid valves are used in an array, these disturbances accumulate.
From a control perspective, solenoid valve arrays also increase software complexity. Each valve must be synchronized with pumps, pressure regulators, and sensors. As workflows grow in complexity and user interfaces become more advanced, maintaining predictable and stable behavior becomes increasingly difficult.
For automated microfluidic systems requiring stable pressure, repeatable flow rates, and clean switching, these limitations often drive engineers to reconsider the valve technology used in the fluidic architecture.
It is important to be clear. Solenoid valves remain an excellent solution when:
In these cases, solenoid valves offer a practical and efficient solution.
But when microfluidic systems require precise control, low internal volume, stable pressure, and scalable automation, engineers increasingly turn to alternative microvalve technologies. This is where rotary valves and motorized valves start to offer clear advantages.
When microfluidic systems require precise control of liquids, rotary valves offer a fundamentally different approach compared to solenoid valves. Instead of relying on elastic deformation or direct acting mechanisms, rotary valves use a controlled rotational movement to define and isolate the flow path. This difference in actuation has a direct impact on precision, efficiency, and reliability.
One of the main benefits of rotary valves in microfluidic applications is their ability to deliver repeatable and predictable flow control. The flow path inside a rotary valve is well defined and mechanically constrained. This allows engineers to maintain stable internal volume, consistent pressure values, and controlled flow rates across repeated switching cycles.
In microfluidic chips, where flow focusing, droplet generation, or volume displacement must remain highly reproducible, even small variations in pressure or internal geometry can affect performance. Rotary valves minimize these variations by offering a stable flow path that does not depend on membrane deformation or elastic recovery.
Internal volume plays a critical role in microfluidic systems. Large internal volumes and dead zones increase liquid consumption, slow down switching, and raise the risk of cross contamination. Rotary valves are particularly well suited for microfluidic flow because they can be designed with very low internal volume and no dead volume.
By reducing trapped liquid and stagnant regions, rotary valves help:
This is especially important for microfluidic applications handling sensitive samples, such as biological fluids, cell suspensions, or rare reagents.
Syringe pumps, pressure regulators, and pressure controllers are commonly used to drive liquid through microfluidic channels. In these setups, pressure stability at the inlet and outlet is essential.
Rotary valves integrate well into pressure-driven fluidic systems because their actuation does not introduce sudden volume changes or sharp pressure spikes.
The controlled rotational movement helps maintain stable output pressure and smooth fluid flow, which is difficult to achieve with solenoid valves in sensitive microfluidic environments.
For applications where the best pressure control is required, such as droplet size control, flow focusing, or long-term experiments, rotary valves provide a more stable solution.
Automation is a key requirement in modern microfluidic systems. Automated platforms depend on predictable valve behavior, consistent timing, and reliable performance over thousands or millions of cycles. Rotary valves are well suited for automated microfluidic systems because their actuation is mechanically controlled and less sensitive to material fatigue.
From a system integration point of view, rotary valves simplify automation by reducing the number of individual components. A single rotary valve can replace multiple solenoid valves, reducing tubing, fittings, and control channels. This simplifies both the hardware setup and the software interface required to control the system.
For engineers looking for an alternative to solenoid valves in microfluidic systems, rotary valves provide clear advantages in terms of precision, efficiency, and reliability. While solenoid valves remain useful for simple tasks, rotary valves are better suited for applications that require:
These benefits explain why rotary valves are widely used in demanding fluidic systems such as chromatography, analytical instrumentation, and advanced microfluidic platforms.
In many microfluidic systems, performance is not only defined by flow rates or pressure values, but also by how fast and how reliably the system can switch between different fluids. Switching time directly impacts throughput, experiment duration, and overall system efficiency.
This is where the difference between solenoid valves and rotary valves becomes very clear.
In a solenoid-based microfluidic setup, each fluid path is typically controlled by an individual solenoid valve. Switching from one fluid to another requires a sequence of actions:
As the number of fluids increases, this sequential logic becomes increasingly slow. The total switching time grows, cleaning cycles take longer, and the system spends more time stabilizing instead of running the actual experiment.
For automated microfluidic systems running repetitive protocols or long experiments, this sequential behavior becomes a bottleneck.
Rotary valves use a different switching principle. Instead of opening and closing multiple individual valves, the flow path is selected mechanically by rotating a single valve core. This allows direct access to the desired fluid path with minimal intermediate steps.
In practical terms, this means:
In multi fluid microfluidic systems, a rotary valve significantly reduces the time required to move from one reagent to the next. This improvement is especially visible in workflows involving frequent reagent changes, wash steps, or alternating buffers.
Automation is not only about speed, but also about control. As microfluidic systems become more automated, the number of components to control has a direct impact on software complexity, user interface design, and system reliability.
Solenoid valve arrays require:
In contrast, a rotary valve acts as a single controlled component. From the point of view of the controller, the system becomes simpler:
This simplification is particularly valuable for OEM systems and custom instruments, where robustness and ease of integration are critical.
During long automated experiments, consistency matters as much as speed. Rotary valves offer stable mechanical positioning, which helps maintain repeatable flow paths and pressure behavior over time. This reduces drift and variability, especially when combined with pressure regulators or syringe pumps in closed loop control systems.
For microfluidic applications that run continuously for hours or days, such as cell culture, incubation, or screening experiments, this stability translates into more reliable results and less need for recalibration or intervention.
Replacing a solenoid valve array with a rotary valve does not only reduce the number of components. It fundamentally changes how the fluidic system is organized. The result is a cleaner architecture with:
This is why rotary valves are increasingly used as an alternative to solenoid valves in advanced microfluidic systems where performance, automation, and efficiency are key requirements.
In microfluidic applications, sample volume is often limited and the cost of reagents can be high. Biological samples, patient-derived material, cells, enzymes, antibodies, or sequencing reagents are frequently available in very small quantities. In these conditions, dead volume and internal volume are not minor details, they directly impact experimental success and operating cost.
Dead volume refers to the portion of the fluidic system that is not actively flushed during normal operation. In microfluidic devices, dead volume can be found in valves, connectors, tubing, and interfaces between components. This trapped liquid leads to several issues:
When microfluidic systems are used for sensitive applications such as cell culture, drug delivery, or diagnostic assays, even small residual volumes can affect results.
Solenoid valves typically rely on flexible membranes or plungers to control flow. While this design is suitable for many industrial fluidic systems, it introduces internal cavities and elastomeric interfaces that are difficult to fully flush at microfluidic scale.
In systems handling multiple fluids, these trapped volumes accumulate across each solenoid valve and connection. As a result, microfluidic systems based on solenoid valve arrays tend to show higher carryover and greater sample loss, especially when switching between incompatible liquids or sensitive biological samples.
Rotary valves are better suited for low volume microfluidic flow because their internal geometry can be tightly controlled. The flow path is defined by solid surfaces and precise alignment, which reduces stagnant regions and limits trapped liquid.
In practice, using a rotary valve in a microfluidic system helps to:
This makes rotary valves particularly attractive for microfluidic applications that require frequent switching between reagents or buffers.
For microfluidic applications involving sensitive samples, protecting sample integrity is as important as controlling flow rates or pressure values. Rotary valves support this goal by providing a stable and predictable flow path with minimal interaction between the liquid and sealing materials.
Reduced dead volume means that less sample remains inside the system after each step. This directly lowers sample consumption and reduces the risk of exposing biological material to incompatible buffers or cleaning solutions.
Reducing dead volume is not only about the valve itself. It is also about system architecture. By replacing multiple solenoid valves with a single rotary valve, engineers can significantly reduce the number of connectors and tubes in the fluidic system.
Fewer components mean:
For microfluidic systems designed for automation or continuous operation, this cleaner architecture plays a crucial role in protecting samples and ensuring consistent performance.
There is no single valve technology that fits every microfluidic application. The choice between solenoid valves and rotary valves should be based on the required level of control, system complexity, sample sensitivity, and automation needs.
Understanding where each solution performs best helps engineers design more reliable and efficient microfluidic systems.
Solenoid valves remain a solid solution for simple fluid control tasks. They are widely available, easy to integrate, and compatible with many industrial control systems. In microfluidic setups where requirements are limited, solenoid valves can be an effective option.
Solenoid valves are well suited when:
For basic liquid handling or non critical microfluidic applications, solenoid valves provide a practical and economical solution.
As microfluidic systems become more complex, the limitations of solenoid valves become more visible. When precise control, low internal volume, and reliable automation are required, rotary valves offer clear advantages.
The AMF On Off rotary valve is designed for microfluidic applications that require:
By replacing arrays of solenoid valves with a single rotary valve, engineers can reduce tubing, fittings, and control channels, while improving overall system reliability.
Choosing between solenoid valves and rotary valves should not be seen as a component level decision only. It is a system level choice that affects:
In many microfluidic projects, solenoid valves are used during early prototyping because of their simplicity. As the system evolves toward more advanced automation, higher throughput, or industrialization, rotary valves often become the preferred solution.
For engineers developing microfluidic devices for research, OEM integration, or industrial applications, it is important to anticipate future requirements. A valve technology that works for a simple setup may become a limitation as the project grows.
The AMF On Off rotary valve is particularly well suited for teams that need a solution capable of scaling from prototype to automated system, while maintaining precise control, efficiency, and reliability.
The advantages of rotary valves become most visible in microfluidic applications where flow control, pressure stability, and low internal volume are critical. While solenoid valves remain suitable for simple tasks, many advanced markets now rely on rotary valve architectures to achieve higher performance and better reliability.
Spatial biology workflows often involve multiple reagents, wash steps, and sensitive biological samples. In these microfluidic systems, reducing dead volume and carryover is essential to preserve spatial resolution and sample integrity. Rotary valves enable clean switching between fluids while maintaining precise flow control across microfluidic chips.
High throughput screening platforms require fast switching, stable pressure values, and repeatable performance over long operating times. Solenoid valve arrays can quickly become complex and difficult to automate at scale. Rotary valves simplify fluidic systems by reducing the number of components, improving switching efficiency, and supporting fully automated microfluidic systems.
In flow chemistry and analytical applications, precise control of flow rates and internal volume directly impacts reaction efficiency and reproducibility. Rotary valves are widely used in chromatography and analytical devices because they provide reliable sealing, low internal volume, and stable long-term operation.
Microfluidic devices for organ on a chip and cell culture often operate continuously for hours or days. Pressure stability, gentle flow control, and protection of sensitive cells are critical. Rotary valves help maintain smooth fluid flow while minimizing pressure fluctuations and sample stress.
Diagnostic microfluidic applications frequently handle patient samples and valuable reagents in very small volumes. Minimizing dead volume and contamination risk is essential. Rotary valves support cleaner fluidic architectures that reduce sample loss and improve reliability in automated diagnostic systems.
For OEM platforms and industrial microfluidic devices, robustness, scalability, and ease of integration are key requirements. Rotary valves offer a durable and predictable solution that scales better than solenoid valve arrays as systems become more complex and automated.
Solenoid valves remain an effective solution for simple fluid control tasks. They are easy to integrate, cost effective, and well suited for basic open or close operations, especially outside microfluidics or in low-complexity systems.
However, microfluidic systems place much higher demands on flow control, pressure stability, internal volume, and automation. As soon as applications involve multiple fluids, sensitive samples, or advanced automated workflows, the limitations of solenoid valves become clear.
Rotary valves provide a proven alternative for these cases. By offering low dead volume, stable pressure behavior, and simplified system architectures, they enable more precise control and more efficient microfluidic designs.
The AMF On Off rotary valve was designed specifically to address these challenges. It does not aim to replace solenoid valves everywhere, but to offer a better solution where precision, efficiency, and reliability are required.
Choosing the right valve technology is not just a component decision, it is a system level choice. For engineers designing modern microfluidic devices, selecting a valve architecture that supports both current needs and future scalability is essential.
If your application is simple, solenoid valves remain a valid option.
If your microfluidic system is complex, automated, or sensitive to volume and pressure, a rotary valve is often the better tool.
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