Integrated sensors, MEMS, and microsystems: Reflections on a fantastic voyage

The past 40 years have seen integrated sensors move from the first micromachined silicon devices to wireless integrated microsystems that combine high-performance batch-fabricated transducers with embedded signal processing and wireless interfaces. This paper reflects on sensor activities during this period, using three of the earliest devices as examples. Neural probes for precision mapping of activity in the central nervous system have evolved from simple acute structures to complex three-dimensional electrode arrays capable of both stimulation and recording. Integrated with circuitry for amplification, multiplexing, spike detection, and the wireless transmission of power and bidirectional data, they are sparking a revolution in neuroscience and are facilitating prosthetic devices for many debilitating neurological disorders. Pressure sensors have moved from low-yield piezoresistive bridges to self-testing wireless capacitive devices hermetically sealed at wafer level. Finally, efforts to miniaturize a gas chromatograph have now realized prototype microsystems the size of a small calculator containing pressure- and temperature-programmed microcolumns able to separate and identify complex gaseous mixtures in seconds. These microsystems will be key in addressing many of the key problems of the 21st century.