How to Validate Your VROC® Chips Before Viscosity Testing
Best Practices for Accurate and Reliable Viscosity Measurements
Proper chip validation is a critical step in ensuring accurate and repeatable viscosity measurements when using VROC® (Viscometer-Rheometer-On-a-Chip) technology. Before running samples, validating your VROC chip confirms that the system is performing within specification and that the measured viscosity values can be trusted.
This application brief outlines recommended procedures for validating m-VROC™ II and Initium One Plus™ chips using viscosity calibration standards.
Why VROC Chip Validation Matters
VROC chips are precision microfluidic devices designed to deliver highly accurate viscosity data across a wide shear rate range. Over time, however, factors such as residue buildup, contamination, or improper handling can impact chip performance.
Validating your chip prior to testing helps to:
Confirm instrument accuracy
Detect contamination or chip degradation early
Reduce data variability
Ensure compliance with internal QA/QC or regulatory requirements
Routine validation is especially important in environments where consistent, high-quality viscosity data is required, such as research labs, production facilities, and quality control settings.
VROC Chip Validation Using Viscosity Standards
To validate your chip, use a viscosity calibration standard, such as a mineral oil or a certified MGVS standard. Follow the steps below for best results.
Step 1: Measure Across Multiple Shear Rates
Measure viscosity at five different shear rates, corresponding to the five measured %FS (full-scale) ranges reported in the software. Testing across multiple shear rates ensures the chip performs accurately throughout its operating range rather than at a single point.
Step 2: Perform Multiple Repeats for Robust Validation
For reliable validation, collect at least 5–10 repeat measurements per shear rate using temperature control. Repeated measurements help reduce random error and provide stronger statistical confidence in the results.
With the m-VROC II and Initium One Plus, this process is simple and efficient because these systems allow unlimited automatic measurements using a single sample volume. This significantly reduces testing time and minimizes sample handling.
In contrast, older systems such as the m-VROC I require manual reloading of the test syringe for each measurement, making the validation process more labor-intensive and time-consuming.
Temperature Control During Validation
Temperature stability is essential for accurate viscosity measurements. Both the m-VROC II and Initium One Plus feature built-in Peltier temperature control, ensuring precise and consistent temperature regulation during validation.
The older m-VROC I system relies on an external water bath, which introduces additional setup complexity and potential temperature variation.
Acceptable % Error Ranges for Chip Validation
Validation results are evaluated by comparing the calculated % error against the acceptable limits defined for each measured %FS range:
A chip is considered validated if the calculated % error is less than or equal to the allowable passing % error and the data segments show a coefficient of determination R² ≥ 0.996. High R² values confirm strong linearity and consistent flow behavior across the tested shear rates.
What to Do If Your Chip Fails Validation
If the calculated % error exceeds the acceptable limits, the chip is not validated and should not be used for sample testing until the issue is resolved. In most cases, performance issues are caused by contamination or residue within the microfluidic channel.
Recommended Actions:
Clean the chip using appropriate solvents
Re-run the validation procedure
If necessary, send the chip for professional servicing
The Initium One Plus simplifies this process with automated multi-solvent chip cleaning, while the m-VROC II uses a dedicated chip cleaning station for efficient maintenance.
The older m-VROC I requires manual cleaning, which involves repeatedly loading cleaning solvents into the test syringe, increasing user effort and variability.
Best Practices for Long-Term Chip Performance
To maintain reliable chip performance over time:
Validate chips regularly
Use clean, filtered samples
Avoid drying residues inside the channel
Follow recommended cleaning protocols after use
Routine validation and maintenance help extend chip life and ensure consistent, high-quality viscosity data.
Summary
Validating your VROC chip before testing is a simple but essential step for achieving accurate, reproducible viscosity measurements. By following proper validation procedures—testing across multiple shear rates, using temperature control, and verifying acceptable error limits—you can ensure your m-VROC II or Initium One Plus system is performing at its best.
With modern VROC systems offering automated measurements, built-in temperature control, and simplified cleaning, chip validation is faster, easier, and more reliable than ever.
Comments
Post a Comment