How far can precision go under viscous stress? Part 2 pushes Kaste Nano II into high-viscosity territory using bulk contact dispensing with larger tubing: CVs <0.6%, 5-µl aliquots, ~70% efficiency across water, buffers, ethanol, glycerol. Positive displacement fluidics conquers back-pressure and valve sticking.
Today’s blog is 855 words long, and a 9 minute read.
Overview
In this second article of the Viscosity Series, we asked oursleves What can Kaste Nano Handle? We tested the Kaste Nano II pump with liquids up to 6 cP viscosity, including buffers and glycerol mixtures. Results show CVs below 0.6%, stable volume delivery across different types of liquids, and with minimal liquid waste —demonstrating reliable performance even with moderately viscous reagents.
Is that the limit? What happens if we push this further?
This installment explores the Kaste Nano II’s performance with high-viscosity liquids (up to 20 mPa·s and beyond) and the transition to bulk (contact) dispensing—a critical strategy for handling fluids that exceed the non-contact dispensing threshold.
The Core Question
At the outset, we have two questions that determine the efficacy of our solutions beyond the initial analysis:
- How does the Kaste Nano II perform when viscosity exceeds the non-contact dispensing threshold?
- What engineering adjustments ensure precision and repeatability under these demanding conditions?
Experimental Setup
Configuration
- Pump: Kaste Nano II (S/N 5123002)
- Tubing: Both standard (5.0 m, 0.03” ID FEP) and custom larger-diameter (1/16” ID FEP, 1.2 m) tubing were tested to reduce back-pressure for viscous liquids.
- Dispensing Tip: 190 µm ceramic nozzle
- Degasser: 480 µl vacuum chamber
- Valves: Standard configuration
Protocols
- Non-contact dispensing: Used for lower viscosities (up to ~6 mPa·s)
- Bulk (contact) dispensing: Used for higher viscosities and as a strategy for stable delivery at the upper viscosity limit
- Aspirated volume: 2200 µl
- Dispensed volume: 1500 µl per run
Tested Liquids
- Water, ethanol, PBS and TBST buffers (with dye)
- Glycerol-water mixtures (50% and 69% glycerol, up to 20 mPa·s)
- Ethanol (for volatility and low surface tension)
Observation #1
Precision Maintained across the Viscosity Range
Regardless of the liquid – buffers, reagents, and ethanol – our performance didnt flinch. We mainted CVs below 0.6% confirming high precision across the viscosity range.
- With standard tubing, the Kaste Nano II achieved CVs of 0.38–0.45% for water and 0.38–0.42% for 50% glycerol (6 mPa·s), even in non-contact mode.
- Using larger-diameter tubing, the pump handled 15–20 mPa·s glycerol mixtures with CVs of 0.41–0.59%, and bulk dispensing of 50% glycerol yielded CVs of 0.38–0.54%.
Takeaway: Regardless of fluid characteristics, the Nano II delivered highly precise volumes with a tight Coefficient-of-Variation (CV), critical for reagent optimization and waste minimization.
Observation #2
Bulk Dispensing Enables High-Viscosity Handling
Bulk dispensing enables high-viscosity, as high aspiration volumes result in pressure build-up for viscous liquids
- Switching to bulk dispensing and larger tubing allowed successful delivery of 69% glycerol (20 mPa·s) and above, with no valve sticking or loss of repeatability.
- Bulk dispensing also minimized issues with droplet formation and surface tension, ensuring reliable delivery to the target.
Design Implication: Selecting dispensing mode and tubing lengths impact dispensing accuracy; switch to bulk dispensing in case of viscous liquids.
Observation #3
Stable Volume Output and Efficiency
Another hallmark of our dispensing solution was preserved, the ability to dispense stable volumes irrespective of the liquid type.
- Across all protocols, the average dispensed volume per aliquot was consistently ~5.0 µl, with minimal drift or variation between runs.
- Dispensing efficiency (dispensed/aspirated ratio) remained high (~70%) for all tested fluids, regardless of viscosity or dispensing mode.
Operational Benefit: Regardless of fluid characteristics, the Nano II delivered highly consistent volumes, critical for assay reproducibility and system robustness.
Observation #4
Robustness to Liquid Properties
Throw a liquid, we will handle it. This is because of our patented displacement mechanism
- Kaste Nano II’s positive displacement mechanism ensured that changes in viscosity or surface tension did not affect volumetric accuracy.
- Buffers with surfactant (TBST) and volatile solvents (ethanol) were dispensed with the same precision as water, demonstrating the system’s versatility.
Operational Benefit: Regardless of fluid characteristics, Kaste Nano works, so you don’t have to change your setup every time you change your reagent.
Practical Implications
- For R&D and production labs: The Kaste Nano II can reliably handle a wide range of viscosities, from water to highly viscous glycerol mixtures, with minimal parameter adjustment.
- For automation engineers: Bulk (contact) dispensing is a robust solution for high-viscosity or challenging fluids, reducing the risk of valve sticking and ensuring consistent delivery.
- For cost-conscious workflows: High dispensing efficiency and low CVs mean less reagent waste, fewer failed runs, and reduced need for recalibration.
Why This Works
- Aspirated through the tip and dispensing is limited by pressure and droplet formation at high viscosities.
- Bulk dispensing, especially with larger tubing, reduces back-pressure and ensures the entire aspirated volume can be delivered without loss or instability.
- The positive displacement design isolates the dispensed volume from viscosity-driven pressure fluctuations, maintaining accuracy.
For fluids >20 mPa·s, adjustments such as larger-diameter tubing or bulk dispensing modes are recommended to maintain pressure stability.
Bottom Line – Why Should You Care
The Kaste Nano II pump demonstrates precision, stability, and efficiency across a wide range of liquid types and viscosities. Whether operating in aspiration or bulk dispensing mode, the system consistently delivers:
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Low CV% (<0.6%) across all fluids
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Constant volume per dispense with minimal variation
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~70% dispensing efficiency, even under challenging conditions
For research and development teams prioritizing accuracy, reproducibility, and flexibility, the Nano II provides a technically robust and integration-ready solution for demanding fluidic environments.
Up next in the Viscosity Series: Strategies for dispensing of viscous liquids – what should you do? Stay tuned!