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PDMD

Non-Contact, Picoliter

PDMD - printing a micro array on a glass surface using an microdispenser

Piezo‑Driven Micro-Dispenser

The Piezo-Driven MicroDispenser (PDMD) enables high-speed, picoliter dispensing starting from 20–30 pL, with up to 1000 droplets per second. Precise volume control is achieved via a piezo ceramic actuator and a digital aspiration/dispense cycle.

This picoliter dispenser is essential for applications like microarray printing, drug screening, biosensors, microfluidics, and printed electronics.
The PDMD integrates seamlessly with all M2 microdispensing instruments.

Picoliter Precision for Every System – Download the Brochure (PDF)

Key Features

  • 1000[nbsp]Hz dispensing frequency
  • Single droplet volume 30[nbsp]pL to 400[nbsp]pL
  • Volume accuracy cv [lt] 2[nbsp]%
  • Different orifice diameters
  • Highly inert borosilicate glass
  • Not coated or treated otherwise

Basic Operation Principle

This picoliter dispenser uses a voltage-driven piezo contraction of 100–250 nm to displace liquid in a glass capillary, ejecting most of it through the nozzle. The contraction is linear with voltage, while the voltage amplitude mainly controls droplet velocity and the pulse width primarily sets droplet volume. Their combined adjustment enables highly controlled, precise liquid dispensing.

Dispensing Modes

  1. Stop-to-spot with Z-moves: The dispenser stops for each droplet deposition and moves up and down between consecutive positions to bypass possible obstacles. These movements cost time but can be necessary when dispensing onto specific locations of a non-planar, 3-dimensional target.
  2. Stop-to-spot, no Z-moves: Without the need to move the head up between consecutive positions, dispensing is much faster. This is always the case when dispensing onto planar targets.
  3. On-the-fly: The dispenser “flies” over the target and releases a droplet on defined positions during the flight. That way, up to 1000 droplets can be deposited, each at its own specific coordinates.

Digital Liquid Handling

Larger volumes are generated as rapid sequences of well-defined picoliter droplets, eliminating the need for individual calibration. This saves time when dispensing multiple volumes in one experiment while maintaining precision and reproducibility.

The demo video shows digital picoliter dispensing at 1000 Hz, where calibrated droplets are sequentially combined to form 0.1, 0.5, 5, 10, and 100 nL, illustrating the method’s flexible volume range.

Aspiration/Dispense Cycle

The aspiration/dispense cycle enables efficient use of precious samples. From just 2 µL, up to 10,000 picoliter aliquots can be dispensed at different target positions, supporting multiple experiments or chip production with minimal sample.

The video illustrates this by aspirating 3 µL of a red solution from a 5 µL droplet and dispensing 150 pL aliquots at various locations. Due to dilution effects, typically about 1 µL of the initial 3 µL can be dispensed without noticeable dilution, depending on mixing (osmosis) and aspiration speed.