Methods, apparatus, and computer program products to form arrays of polymers each having a pattern of features on a surface of a flexible elongated web, comprising. In a method polymers or their precursor units are applied at an application station to the surface. Multiple features are covered at a reagent station with a continuous volume of reagent which chemically reacts with precursors or the web. The flexible elongated web is driven in a lengthwise direction through the application station. This sequence may be repeated as needed to form the arrays along the web. Also provided is a method preparing a surface of a flexible elongated web to receive a biopolymer array.