Bio-Inspired Sensors

By Paul Wolf

Practical detection of explosive, highly combustible, or toxic chemical agents, as well as biological agents, requires improved and expanded sensor and sensor systems. Developing sensors that discriminate signals originating from a complex background in addition to being lightweight and sensitive is particularly challenging. In certain regions of the electromagnetic spectrum, commercially available sensors have a rather limited capability and the ability to efficiently detect trace amounts of chemical and biological species with high sensitivity and confidence has yet to be achieved.

Nature, conversely, has produced extraordinary sensory systems in biological species that exceed the capabilities of a broad range of man-made sensors. Understanding the physical, chemical, and biological processes that are responsible for these sensory abilities may produce a blueprint for replicating or reconstructing them in man-made devices. Research involving the mimicry of biological systems, called biomimetics, is a branch of biotechnology that abstracts good designs from nature to enable, design and develop new man-made materials and structures. This interdisciplinary field, which engages researchers from the field of biology, materials science, engineering, chemistry and physics, provides opportunities to develop new technologies by exploiting nature's designs and achievements.

The diversity and resourcefulness of biological sensing are enormous and largely unexplored. For example, pit vipers use extremely sensitive infrared/thermal detection to locate prey, and beetles employ their infrared detection system to locate suitable breeding grounds. Understanding these ingenious biological designs could lead to the development of room temperature sensors that would replace cryogenic photonic detectors that dominate the infrared sensor community and exceed their performance. The remote detection of explosives is particularly important and poses a unique challenge. Current explosive detectors use x-ray imaging to look for signs of devices and stationary ion mobility spectrometers or chemiluminescence sensors to detect specific explosive compounds. The latter detectors, however, require the physical collection of samples to surmount the limited sensitivity of these detection systems. Alternatively, the canine nose is a remarkable organ. About 100 times more sensitive than the human nose, it can detect explosives, drugs and even humans whose signatures are buried in a complex sea of scents. A dog can track by maintaining a constant sensory flow across their olfactory epithelium and following the scent gradient to the source. Detailed studies to better understand dogs' abilities could be useful in designing more effective, manufactured sensor systems.

Ascertaining mechanisms that biological organisms use to sense electromagnetic radiation outside the visible region or detect trace amounts of biological and chemical agents is one goal of bio-inspired sensor development. Identifying nature's specific and efficient solution for detection schemes and decoding these expressions of biological principles observed in a living organism are the first steps in developing novel synthetic materials, processes and sensors. Subsequent challenges quickly fall into the realm of materials science, nanobiotechnology and engineering. Duplicating and reconstructing these natural processes by converting biological responses into usable signals, developing new materials that function like biological systems, and engineering the natural traits of these sensory systems are required to produce a new class of broadly applicable sensors and sensor systems.