The present disclosure provides an antimicrobial substrate including a substrate and a polythiophene polymer. The polythiophene polymer has a number of repeated monomer units from n is 5-14 or 30 to 120, a number average molecular weight (Mn) from 1,000 to 4,000 or 10,000 to 40,000; and a polydispersity index (PDI) from 1 to 1.3. The present disclosure also provides the polythiophene polymer and uses thereof.