Methods and devices are provided for preparing a protein array having a plurality of proteins. In one embodiment, the method includes providing a plurality of nucleic acids each having a predefined sequence and expressing in vitro a plurality of proteins from the plurality of nucleic acids. In another embodiment, protein arrays having a solid surface and a microvolume are also provided. The solid surface can have a plurality of anchor oligonucleotides capable of hybridizing with a plurality of nucleic acids. The microvolume can cover each of the plurality of anchor oligonucleotides and can be configured to produce a polypeptide from each of the plurality of nucleic acids.