When 1:00 PM - 3:00 PM Apr 09, 2015
Where GM Conference Room, Lurie Engineering Center
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Energy-efficient Multifunctional Sensors based on Semiconductor Devices


Kanika L. Agrawal
Thesis Defense

Max Shtein, advisor

 

The growing potential of telemedicine and on-body health monitoring has led to the emergence of a new set of challenges associated with chemical, biological and other kinds of sensors that may be needed to facilitate integration with wearable devices. This thesis is aimed at addressing some of these challenges via the use of novel semiconductor device architectures in ways that facilitate significant advances in energy efficiency, miniaturization and cost effectiveness of traditional sensing techniques.

For displays, organic light emitting devices (OLED) offer several unprecedented advantages over conventional displays, including flexibility, compactness, and superior power efficiency. However, the touch sensing capability in such devices is usually provided by capacitive or resistive sensors overlaid on the main display that increase bulkiness. Integration of touch sensing with the imaging plane of the display could dramatically reduce thickness, improve reliability, and enhance sensing resolution. This thesis reports a novel physical effect in OLEDs that could allow touch sensing to be performed by the image-forming pixel itself. In addition to studying the fundamental physical mechanism by which this sensing proceeds, an efficient single pixel OLED that generates changes in electrical current upon touch is discussed. The work presented here outlines how the effect demonstrated could also be used for refractive index mapping of phase-segregated materials and in near-field microscopy applications.


Another new challenge in wearable electronics is limited on-board power, due to growing power requirements to support a larger number of functions, and a relatively low energy density of batteries. At the same time, a considerable amount of research in recent years has been dedicated to developing novel biochemical sensors that can be integrated with wearables. To address these two emerging challenges, a modified dye-sensitized solar cell is designed to detect common contaminants in drinking water (e.g. metal ions), while powering its own operation by converting absorbed ambient light into an electrical signal. The sensing mechanism is analyzed in detail and strategies for improved sensor design are proposed.

Finally, ultra-sensitive chemiluminescence detection is demonstrated with an unprecedented, ~100 picomolar sensitivity, applicable to a wide variety of substances, ranging from environmental contaminants to biomarkers. This is achieved by using a light concentrator structure akin to an integrating sphere, filled with a luminescent solution, optically coupled to a low-cost photodetector. The structure is highly miniaturizable and can be used, for example, with a camera sensor in a mobile phone, potentially unlocking a broad range of field and point-of-care diagnostics.