Desired numbers of proteins can be positioned on surfaces by using dip-pen nanolithography (DPN). Ferritin nanoarrays are fabricated by direct-writing nanodroplets of a ferritin solution on transmission electron microscopy surfaces. After the contact-angle value of these droplets is determined, the concentration of the inking protein solution and the diameter of the dot-like feature can be modulated to position a single ferritin particle on a surface (see figure).