Microfluidic valves are essential components in microfluidic systems. They control the movement of liquids and gases inside microchannels, allowing precise flow routing, isolation, switching, and timing.
Choosing the right valve architecture has a strong impact on system performance, reliability, contamination risk, and overall complexity.
Here you have an overview of microfluidic valve types, how they work, how to compare them, and how they are used in real microfluidic applications.
Microfluidic valves can be classified in several ways. The most common distinction is between passive valves and active valves, based on whether external actuation is required.
Passive microvalves operate without external power or control signals. Their behavior depends on geometry, material properties, surface tension, or pressure differences.
Common passive valve types include:
Passive valves are often used in disposable microfluidic chips, especially for simple flow control or safety functions.
Advantages
Limitations
Example of a passive microfluidic burst valve, Hansang Cho et al., Colloid and Interface Science, 2007, DOI: 10.1016/j.jcis.2006.10.077
Active valves require an external actuation mechanism to open, close, or redirect flow. They offer much higher control and repeatability.
Common active valve families include:
Active valves are widely used in reusable systems, automated platforms, and industrial microfluidic devices.
Microfluidic valves control fluid flow by modifying the flow path, blocking channels, or redirecting liquids between ports. This is achieved using different actuation mechanisms.
Pneumatic valves typically use a flexible membrane, often made of PDMS. Applying air pressure deforms the membrane, closing or opening a microfluidic channel.
They are widely used in academic research and lab-on-a-chip devices.
Key points
Example of pneumatic microvalves, from Xuling Liu and al, Energies, 2022, DOI: 10.3390/en15218094
Solenoid valves use an electromagnetic coil to move a plunger or seal.
They are commonly used for:
Example of Solenoid 2/2 utilization
Rotary valves use a rotating element to connect different ports through defined internal channels. They are often used for distribution, switching, or recirculation tasks.
Typical functions include:
Rotary valves are common in analytical instruments, chemical analysis systems, and automated fluid handling platforms.
Example of an AMF rotary valve
Microfluidic flow control refers to the ability to precisely regulate how fluids move inside microfluidic channels. This includes controlling flow rates, defining the direction of flow, managing timing, and sequencing multiple fluids within a system. These functions are essential for ensuring repeatable and reliable operation of microfluidic devices.
Flow control in microfluidics is achieved through the combined use of valves, pumps or pressure regulators, and, in many cases, sensors. While pumps and pressure sources generate fluid motion, valves play a central role by determining where fluids go and when they are allowed to move. They define flow paths, isolate channels, and enable switching between different fluidic routes.
Several parameters are critical when evaluating a microfluidic flow control system. Flow rate stability affects measurement accuracy and process reproducibility. Response time determines how quickly the system can react to control commands. Internal dead volume influences sample loss and dilution, while carryover and contamination risks are especially important when working with sensitive or valuable fluids.
In precise microfluidic systems, the choice of valves is therefore often as important as the choice of pumps. Even with a highly accurate pumping solution, poor valve selection can limit overall system performance and reliability.
There is no universal valve solution in microfluidics. Comparing microfluidic valves requires looking at their impact at system level, rather than focusing only on individual specifications. The same valve can perform very differently depending on how it is integrated into a complete fluidic setup.
A first comparison criterion is flow control capability. Some valves are designed for continuous flow, while others operate in a discrete on or off manner. The ability to handle bidirectional or unidirectional flow also matters, as well as the usable flow rate range. These aspects directly influence how flexible and precise the fluid routing can be.
Internal volume is another critical factor. Dead volume inside a valve can lead to sample loss, dilution, or delayed response. In systems handling multiple fluids, internal geometry also affects carryover between fluids, which is particularly important when working with sensitive reagents or biological samples.
The actuation method strongly influences both performance and system complexity. Pneumatic, electrical, and mechanical actuation technologies each come with different requirements in terms of power consumption, control hardware, and software complexity. Actuation speed and stability can also vary significantly between valve types.
Integration constraints must also be considered early in the design process. Some valves are fully integrated at chip level, while others require external tubing and fittings. Footprint, mounting options, and mechanical interfaces can have a major impact on system layout and scalability.
Finally, reliability plays a key role, especially in automated or long-term applications. Valve lifetime, sensitivity to particles, and maintenance requirements determine how robust a system will be over time and how often it needs intervention.
A simple comparison between solenoid valves and rotary valves illustrates these trade-offs. Solenoid valves are well suited for basic on or off control or venting functions. However, when multiple solenoids are combined to build complex fluid routing, the system can quickly become bulky and harder to clean. Rotary valves, in contrast, offer integrated routing with well-defined flow paths, which can reduce tubing, dead volume, and control logic. That said, they are not always necessary for simple functions.
Ultimately, the right choice depends on the application requirements and system constraints, not on the valve type alone.
Important valve features directly influence system performance.
Precision and repeatability
High-precision valves ensure stable flow control and reproducible results, especially in analytical and biomedical applications.
Reliability
Valve lifetime, sealing quality, and resistance to wear are critical in continuous or industrial systems.
Energy consumption
Passive valves consume no energy. Active valves vary widely depending on actuation technology.
Material compatibility
Valves must be compatible with:
Material choice affects adsorption, swelling, and long-term stability.
Microfluidic valves are used across a wide range of scientific, biomedical, and industrial fields. Their role is to control fluid movement with precision, reliability, and repeatability, often under very different operating constraints depending on the application.
In biomedical applications, microfluidic valves are central to drug delivery systems, where accurate dosing and timing are required. They are also widely used in cell culture platforms and organ-on-chip devices, where stable flow conditions and gentle handling of biological samples are essential. Diagnostic devices rely on valves to sequence reagents, isolate samples, and manage washing steps, while applications such as blood analysis or glucose monitoring require valves with low dead volume and minimal carryover to ensure accurate measurements.
In chemical analysis, valves are used for sample preparation, reagent mixing, and fluid routing between different analytical modules. They play an important role in systems interfacing with chromatography equipment, where precise injection volumes and clean flow paths are critical. Microfluidic valves are also used to connect microfluidic devices to mass spectrometry systems, where controlled transfer of small sample volumes is required without contamination or dilution.
Beyond laboratory applications, microfluidic valves are increasingly used in industrial and environmental systems. In chemical synthesis, they enable controlled reagent addition, reaction sequencing, and process optimization at small scales. Environmental monitoring platforms use microfluidic valves to handle water or air samples, perform on-site analysis, and automate sampling cycles. In quality control and process automation, valves support reliable and repeatable fluid handling in compact and integrated systems.
In food and beverage testing, microfluidic valves support automated analysis of liquids such as water, milk, wine, or juices. They enable controlled sampling, dilution, and reagent addition in compact testing platforms used for quality control, safety monitoring, and contamination detection. Chemical compatibility and ease of cleaning are particularly important in these environments.
Microfluidic valves are also widely applied in biosensing systems. In these applications, valves control the delivery of samples, buffers, and washing solutions to sensing areas, helping to improve signal stability and repeatability. Low dead volume and precise flow control are essential to reduce background noise and ensure reliable detection, especially when working with low-concentration analytes.
Additional applications include forensic analysis, materials research, microreactor platforms, inkjet and printing technologies, and portable analytical devices. Each of these use cases places different constraints on valve selection, particularly in terms of cleanliness, precision, chemical compatibility, lifetime, and scalability.
As a result, valve choice must always be aligned with the specific requirements of the application rather than based on a single performance metric.
A practical selection approach includes the following questions:
In many systems, multiple valve technologies are combined to leverage the strengths of each.
Advanced Microfluidics designs and manufactures microfluidic rotary valves and fluid handling components for research, OEM, and industrial systems.
Rather than focusing on a single valve type, the approach is based on system architecture and application constraints.
AMF develops rotary valve platforms covering three main functions:
These architectures are typically used when flow paths must be clearly defined, repeatable, and easy to manage at system level.
Rotary architectures are designed to minimize dead volume and reduce carryover between fluids, which is critical for sensitive or valuable samples.
Valve design and manufacturing are based on high-precision mechanical know-how, allowing stable positioning and repeatable fluid routing over time.
Valves are developed as components that can be integrated into larger fluidic systems, including syringe pumps, pressure-driven setups, and automated platforms.
Valve configurations, materials, port layouts, and interfaces can be adapted to specific application needs, from early prototypes to industrial systems.
Rotary valves are not positioned as replacements for all solenoid or pneumatic valves. They are used where they bring clear benefits in routing simplicity, cleanliness, and system robustness.
In many real-world microfluidic systems, solenoid valves, pneumatic valves, and rotary valves coexist. Each technology answers different constraints related to flow control, cost, integration, and performance.
Understanding these differences allows system designers to build more reliable and efficient microfluidic devices.
AMF focuses on providing well-defined rotary valve architectures that fit naturally into this broader valve ecosystem.
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