How the reusable pen works

The reusable pen is a precision volumetric dispensing device for a 3 mL cartridge. This guide explains how the mechanism meters consistent, repeatable volumes — purely as device documentation.

Research use only — a dispensing device, not dosing guidance. This explains the mechanics of measuring and dispensing volumes of reconstituted solutions for in-vitro laboratory research. It is not guidance on human or animal use, it does not cover administration technique, and it contains no dosing protocols. Researchers determine the volumes appropriate to their own experiments.

The components

• Dose knob — turned to set the increment.
• Tactile click ratchet — gives an audible/feelable "click" per increment.
• Threaded push-rod — converts rotation of the knob into linear travel.
• Plunger — driven forward by the push-rod to displace solution from the cartridge.
• 3 mL cartridge — holds the reconstituted research solution.
• Needle hub and needle — the dispensing tip.

How a "click" works

Turning the dose knob rotates the threaded push-rod, which advances the plunger forward by a fixed, precise amount. The ratchet produces one tactile click per increment, so each click is a discrete, repeatable step rather than a free-running slide. Mechanically, one click = 1/300th of a full plunger advance.

Volume per click

The arithmetic follows directly from the cartridge size and the increment:

• Full cartridge volume: 3.0 mL
• One click: 0.01 mL
• Total clicks per cartridge: 3.0 mL ÷ 0.01 mL = 300 clicks

That fixed 0.01 mL step is the whole point of the device — it lets you dispense the same small volume consistently, which is what makes measurements repeatable across a study.

Priming

Before measuring, a number of initial priming clicks are used to expel air from the cartridge and needle path so that subsequent clicks dispense liquid rather than air. This is a one-off mechanical preparation step, not part of measuring a volume.

Why precision matters in research

Repeatability is everything in a research workflow: a device that delivers the same 0.01 mL per click removes a source of variability, so results can be attributed to the compound rather than to inconsistent handling. Start from a verified material with a batch-specific Certificate of Analysis, store solutions correctly (storage guide), and choose an appropriate solvent (bacteriostatic water & stability).

See the Reusable Auto-Injector Pen or browse the full catalogue.