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Measuring single microliter droplets

APPLICATION NOTE

Introduction

This application note shows how the Pulsed Flow Sensor (PFS) can be used in combination with a micro valve (B-drop mini) to measure single droplet volumes from 0.2 to 16 µl.

Used Material

  • Pulsed Flow Sensor
  • PFS controller with User Interface
  • B-drop mini
  • Pressure supply 0.5 bars
  • Water container 300 ml
  • Silicone Tubing
droplet measurement

Experiment setup

The PFS was connected to a B-drop mini in a vertical setup. The tube between sensor and valve was kept as short as possible to prevent damping.

The system was then pressurized to 0.5 bars (without pressure control) and the measurement mode was set to “Droplet Mode”. Then the valve was triggered with different opening times using the following waveform.

peak hold graph

Measurements

For 5 different opening times the droplet volumes were measured with the Pulsed Flow Sensor. The measured diagrams show that for the shortest opening time (2 ms) the valve already closes before a constant flow plateau can be reached. Still a good repeatability can be achieved. Longer opening times lead to smaller influence of the opening and closing process of the micro valve and  therefore show better repeatability.

Time-Flow graph measuring single microliter droplets

Measured data

Opening time of the valve chart