Microfabricated chemical sensors, advantages

Microfabrication technology used to manufacture microreactors also introduces many advantages, most notably the ability to rapidly and cheaply mass-produce devices. The low cost of microfabricated devices makes it possible for these devices to be disposable, a characteristic desirable for many medical applications. Rapid scale-up of production by operating many microreactors in parallel can also be accomplished. Microfabrication also presents the opportunity for complete systems in a single monolithic device or systems on a chip as microreactors are incorporated with chemical sensors and analysis devices, microseparation systems, microfluidic components, and/or microelectronics. 

The term pTAS is sometimes interchanged with lab-on-a-chip (LOG), more often when the manipulation of fluids is involved. pTAS and LOG range in size from a few microns to a few millimetres. The technique of pTAS is interdisciplinary it combines the advantages of chemical sensors and the resolving power of modem benchtop analytical systems and is constantly evolving. The main advantage of pTAS is integration of the entire separation process onto one analytical microdevice, so early efforts focused on micropumps and valves to manipulate fluids inside a microfabricated structure. In such a fluid-based pTAS,... 

Not long ago,this group first described microelectrochemical devices, which are based on microfabricated arrays of electrodes, connected by electroactive materials. Because the active components of these devices are chemical in nature, many of these devices are chemically sensitive,and comprise a potentially useful class of chemical sensors. Devices showing sensitivity to pH, 02r 2 f and Na" have been demonstrated. These devices are, typically, operated in fluid solution electrolytes. If this class of devices is to be useful as gas sensors, systems which are not dependent on liquid electrolytes need to be developed. We have recently reported solid state microelectrochemical transistors, which replace conventional liquid electrolytes with polymer electrolytes based on polyethyleneoxide (PEG) and polyvinylalcohol (PVA). In this report, we discuss additional progress toward solid-state devices by employing a new polymer ion conductor based on the polyphosphazene comb-polymer, MEEP (shown below). By taking advantage of polymer ion conductors we have developed microelectrochemical devices, where all of the components of the device are confined to a chip. 

A MEMS-based biosensor is a biosensor which is realized by microfabrication technology and takes advantage of the small size. It incorporates a biological component with a physiochemical transducer such as a microsystem. It is a special class of chemical sensor that takes advantage of the high selectivity and sensitivity of biologically active materials. It involves immunoenzyme and microorganism sensors. 

The sensors desaibed above do not represent the complete range of those available, particularly for gas phase sensors. However, they do represent a significant number of the types of selectivity and transduction schemes that have been used commercially. A key point to make is that many of these sensors were developed through trial and error, and most took advantage of materials that were already available or that could be easily adapted to the application. It seems likely that further development in selective interfaces for chemical sensors will require novel materials, microfabrication strategies, and/or signal transduction techniques. 

---