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U.S. Food and Drug Administration

Measuring Flow Resistivity in Microfluidics-Based Medical Devices

Catalog of Regulatory Science Tools to Help Assess New Medical Devices 

This regulatory science tool is a lab method to measure flow resistivity in microfluidic-based devices, which may be used to identify flow-related failure modes (e.g., bubbles, leakage). 

Technical Description

This regulatory science tool (RST) provides a methodology to measure flow resistivity, also called hydrodynamic or fluidic resistance, for microfluidic medical devices. Flow resistivity denotes the innate opposition that physical elements (e.g., microscale channels) exert on the internal fluid flowing through these elements. Measuring flow resistivity is particularly important in the early life cycle of microfluidic medical device development to accurately measure flow rates and pressure, and to specify flow parameters that may impact device performance. The flow resistivity data can be used to identify commonly occurring failure modes such as bubbles, leakage, and clogging in microfluidic devices. 

Intended Purpose 

A microfluidic device developer may use this protocol to measure the flow resistivity of a straight microfluidic channel to ensure that their chosen pumping mechanism delivers flow rate accurately. In addition, this method may assist developers in determining if flow and pressure sensors are appropriate based on the fluid properties and application, within operational range, and are accurate for their intended application. After performing this assessment, the developer may use the same flow and pressure sensors to measure the flow resistivity of their own device design. This tool may also assist in troubleshooting potential failure modes.

Testing

The publication provided in the supporting documentation describes the method. The User Manual provides a step-by-step protocol including flow resistivity values for a commercially available straight microfluidic channel with a cross-sectional area of 100 µm x100 µm (per provider specifications). This tool may be used as an early stage comparator for manufacturers to characterize their flow and pressure sensors before using those sensors for assessing their device flow performance. This tool was validated by comparing the experimentally obtained values with analytical solutions expected based on the geometry of the device used. 

Limitations

The tool is developed based on a generic microfluidic channel and device-specific considerations were not evaluated. The technical limitations of the lab method are provided in the User Manual. 

Supporting Documentation

  1. Bozorgnezhad, Ali; Herbertson, Luke; Guha, Suvajyoti. Measuring Flow Resistivity in Microfluidics based Medical Devices. Summer Biomechanics, Bioengineering and Biotransport Conference. June, 2024. (https://sb3c.org/wp-content/uploads/2024/SB3C2024_Proceedings_Book.pdf)
  2. User Manual

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