Peptide libraries have been broadly recognized as useful sources for screening bioactive ligands that bind to receptors and enzymes, as powerful tools for studying antibody-antigen interactions, and for searching detailed information about protein-protein interactions etc. Also, this approach has been widely used by the drug industry to discover biologically active compounds. Existing methods for constructing peptide libraries include multipin synthesis, tea-bag method, split synthesis, and light-directed combinatorial library construction.