Sensors are the devices or subsystems that are used for the detection of events and changes in its environment. They collect the information and send it to other electronics. They are used in the objects of everyday use such as touch-sensitive elevator buttons. Two of the common types of sensors include chemical sensors and biosensors. Chemical sensors are the analytical devices that are able to provide information about the chemical composition of their environment. Biosensors are the sensors that detect analytes through biological components such as cell, proteins and nucleic acids. Actuators are the constituents of machines that are responsible to move and control a mechanism. This book presents the complex aspects of sensors and actuators in the most comprehensible and easy to understand language. It aims to shed light on some of the unexplored aspects of such fields. This textbook provide comprehensive knowledge to the readers.