This book equips its readers with fundamental concepts and a comprehensive understanding of the principles and functionality of biosensors. This book focuses on various biosensor technologies like field effect transistors (FET), plasmonics, bioresorbable biosensors, electrochemical biosensors, etc., and their applications. The book also covers the reliability aspects and challenges in biosensor development that are a major cause of erroneous calibration and even failure. The book also features the concept of bio receptors, immobilization techniques, target-receptor interactions, surface energy changes, sensitivity, selectivity, etc. This would be an ideal reference for researchers and scholars studying biosensors realized with various material sets and technologies including state-of-the-art modern materials and innovative techniques.