The wetting properties of structured self-assembled monolayers are used to fabricate sample target substrates for MALDI-TOF mass spectrometry. Combining the advantages of a hydrophobic-hydrophilic surface pattern and the possibility of obtaining micrometer patterns allows an increase in the sensitivity of MALDI-TOF mass spectrometry analysis and a reduction in the traceable concentration down to fmol mu L-1. This easy, cheap and fast patterning process provides substrates that allow sensitive, high-resolution mass spectrometry of dilute solutions.