Biomedical Engineering Reference
In-Depth Information
17.4.2 Linearity and Dynamic Range ......................................................487
17.4.3 Spectral Response ..........................................................................488
17.4.4 Response Time ................................................................................488
17.4.5 Pixel Uniformity ..............................................................................490
17.4.6 Array Performance Under Mechanical Bending ........................491
17.5 Application—Motion Detection ..................................................................................491
17.5.1 Overview of Motion Detection ......................................................................491
17.5.2 Motion Detection Algorithm ..........................................................................492
17.5.3 Implementation ................................................................................................493
17.5.4 Experimental Setup and Results ....................................................................495
17.6 Conclusions ....................................................................................................................495
17.6.1 Overview ..........................................................................................................495
17.6.2 Limitations and Recommendations ..............................................................497
Acknowledgments ....................................................................................................................498
References ....................................................................................................................................498
17.1
Introduction
17.1.1
Bioelectronics
Bioelectronics, first defined by visionary biologist Albert Szent-Gyorgyi in 1968, has
emerged as one of the most rapidly expanding interdisciplinary research frontiers (1).
As silicon-based devices continue to reduce in scale, their limitations become evermore
apparent. Future developments indicate that electronic systems will migrate to systems
that are based on organic or biological materials. Evolution has optimized biomaterials
to exhibit highly dynamic characteristics at the molecular scale in ways that cannot be
attained by current technologies. First, biological systems can store and process large
amounts of information in extremely compact structures. Second, biological devices are
assembled from individual molecules that are arranged spatially with respect to one
another. Third, biological systems are extremely sensitive to their surroundings and are
able to detect and discriminate changes in the environment. The performance of bio-
logical materials, united with their small size, energy efficiency, and inexpensive fabri-
cation techniques, make them a promising alternative for designing various sensing
devices.
Photosensitive proteins that can convert light directly into an electrical signal are
becoming widely investigated biomaterials. Their optical and photoelectric features per-
mit them to behave as “smart materials” in various signal processing and image sensing
applications. Over the past three decades, biochemists and biophysicists have studied the
structures and functions of such proteins in detail. Among them, bacteriorhodopsin (bR)
is the most notable example. It exhibits light-sensitive characteristics similar to that of
rhodopsin
, a protein found in human eyes. Compared with other protein photoreceptors,
bR is highly resistant to thermal and photochemical degradation, thereby exhibiting excel-
lent long-term stability. As bR shows application potential in low-light detection, artificial
vision, parallel associative processors and memories, it is quickly becoming an advanced
material for constructing bioelectronic devices.
