This paper offers an introduction to the technological advances of image sensors designed using complementary metal-oxide-semiconductor (CMOS) processes along the last decades. We review some of those technological advances and examine potential disruptive growth directions for CMOS image sensors and proposed ways to achieve them. Those advances include breakthroughs on image quality such as resolution, capture speed, light sensitivity and color detection and advances on the computational imaging. The current trend is to push the innovation efforts even further as the market requires higher resolution, higher speed, lower power consumption and, mainly, lower cost sensors. Although CMOS image sensors are currently used in several different applications from consumer to defense to medical diagnosis, product differentiation is becoming both a requirement and a difficult goal for any image sensor manufacturer. The unique properties of CMOS process allows the integration of several signal processing techniques and are driving the impressive advancement of the computational imaging. With this paper, we offer a very comprehensive review of methods, techniques, designs and fabrication of CMOS image sensors that have impacted or might will impact the images sensor applications and markets.
Elevated cholesterol levels are associated with a greater risk of developing cardiovascular disease and other illnesses, making it a prime candidate for detection on a disposable biosensor for rapid point of care diagnostics. One of the methods to quantify cholesterol levels in human blood serum uses an optically mediated enzyme assay and a bench top spectrophotometer. The bulkiness and power hungry nature of the equipment limits its usage to laboratories. Here, we present a new disposable sensing platform that is based on a complementary metal oxide semiconductor process for total cholesterol quantification in pure blood serum. The platform that we implemented comprises readily mass-manufacturable components that exploit the colorimetric changes of cholesterol oxidase and cholesterol esterase reactions. We have shown that our quantification results are comparable to that obtained by a bench top spectrophotometer. Using the implemented device, we have measured cholesterol concentration in human blood serum as low as 29 µM with a limit of detection at 13 µM, which is approximately 400 times lower than average physiological range, implying that our device also has the potential to be used for applications that require greater sensitivity.
Infrared plasmonic filters, consisting of subwavelength hole arrays etched into metal films, exhibit characteristics that are typically associated with the formation of surface plasmon polaritons, namely enhanced transmission and wavelength filtering of the incident light. In this article, the properties that dictate the plasmonic response of a material from the optical to the infrared regime are investigated, followed by the design, simulation, fabrication and characterisation of an infrared plasmonic filter set. Infrared plasmonic filters have also been integrated with optical plasmonic filters and a terahertz metamaterial to create a new hybrid multi-spectral material that can filter blue, green, red, near infrared, short wave infrared and two mid infrared wavelengths whilst simultaneously absorbing a single terahertz frequency. The multispectral material could be integrated with appropriate image sensors to create a multi-spectral camera capable of operating at optical, infrared and terahertz wavebands simultaneously.
The measurement of nanophotonic sensors currently requires the use of external measuring equipment for their read-out such as an optical spectrum analyzer, spectrophotometer, or detectors. This requirement of external laboratory-based measuring equipment creates a "chip-in-a-lab" dilemma and hinders the use of nanophotonic sensors in practical applications. Making nanophotonic sensors usable in everyday life requires miniaturization of not only the sensor chip itself but also the equipment used for its measurement. In this paper, we have removed the need of external measuring equipment by monolithically integrating 1-D grating structures with a complementary metal-oxide-semiconductor (CMOS) integrated circuit having an array of photodiodes. By doing so, we get a direct electrical read-out of the refractive index changes induced when applying different analytes to grating structures. The gratings are made of CMOS compatible silicon nitride. Employing a nanophotonic sensor made of CMOS compatible material allows fabrication of the integrated sensor chip in a commercial CMOS foundry, enabling mass production for commercialization with low cost. Our results present a significant step toward transforming present laboratory-based nanophotonic sensors into practical portable devices to enable applications away from the analytical laboratory. We anticipate the work will have a major impact on technology for personalized medicine, environmental, and industrial sensing.
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