Biosensors & Bioelectronics

Gas Sensors

A Gas Sensor is a device that detects the presence of gases in an area, often as part of a safety system. This type of equipment is used to detect a gas leak and interface with a control system so a process can be automatically shut down. A gas detector can sound an alarm to operators in the area where the leak is occurring, giving them the opportunity to leave. This type of device is important because there are many gases that can be harmful to organic life, such as humans or animals. Metal oxide-based resistive-type gas sensors are solid-state devices which are widely used in a number of applications from health and safety to energy efficiency and emission control. Nanomaterials such as nanowires, nanorods, and nanoparticles have dominated the research focus in this field due to their large number of surface sites facilitating surface reactions. Previous studies have shown that incorporating two or more metal oxides to form a heterojunction interface can have drastic effects on gas sensor performance, especially the selectivity. Interdigitated capacitive transducers have been inkjet printed onto flexible substrates and optimized for gas sensing applications. Their characteristics have been improved by tuning the annealing/sintering conditions and making use of additional passivation procedures, such as Ag electroplating with Ni or Parylene-C coating of the whole device surface. Surface acoustic wave sensors are a class of micro-electromechanical systems (MEMS) which rely on the modulation of surface acoustic waves to sense a physical phenomenon. The sensor transducers an input electrical signal into a mechanical wave which, unlike an electrical signal, can be easily influenced by physical phenomena. The device then transduces this wave back into an electrical signal. Changes in amplitude, phase, frequency, or time-delay between the input and output electrical signals can be used to measure the presence of the desired phenomenon. The calorimetric gas sensor is a device which uses calorimetry as the transduction principle and operates by measuring the heat of a reaction on the sensor surface. It is known that the exothermic nature of the combustion (the oxidation reaction) causes a rise in temperature.