A simple pen-spotting method for arraying biomolecules on solid substrates

We describe a simple, relatively inexpensive method for depositing biomolecules on a solid substrate using Rapidograph drafting pens. The pens can be used without modification to accurately deposit spots between approximately 100 and 600 microm in diameter. When mounted on a suitable microtranslation stage, the pens can be used to easily deposit tens of spots aligned with underlying substrate features such as microfabricated sensors. The pens are particularly convenient because pre-mixed solutions can be stored in the pens for multiple uses. We demonstrate the use of this approach to deposit DNA probes on a microsensor array.