This book equips its readers with fundamental concepts and a comprehensive understanding of the principle and functionality of biosensors. This book focuses on various biosensor technologies like field effect transistor (FET), plasmonics, bioresorbable biosensors, electro-chemical 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.