ENHANCED VISION - INFRARED 1

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1 ENHANCED VISION - INFRARED 1 Enhanced Vision - Infrared Yoko Frayer Annamaneni Sriharsha Marija Nikolikj- Stojmanovska Paulo Van Hove Nanotechnology and Nanosensors by Prof. Hossam Haick

2 ENHANCED VISION - INFRARED 2 Table of Contents Abstract.. 3 Introduction. 4 Literature Review. 5 Project Description. 6 Conclusions and Recommendations References. 10

3 ENHANCED VISION - INFRARED 3 Abstract Infrared detection is the application that will be clarified in this paper. This application can be accomplished by using contact lenses together with photodetectors or microbolometers. Both of these methods will be explained in this paper. A photodetector consist of a DC- voltage and a vanadium oxide layer. This vanadium oxide layer will be used to detect the IR wavelengths. Microbolometers consist of two electrodes, a reflector, a gold contact and an IR absorbing material. In accordance with the intensity of the IR- signal the brightness of a LED will change. The contact lenses will consist of three layers. This layers contain piezoelectric components, LED, a sensor and a electronic system.

4 ENHANCED VISION - INFRARED 4 Introduction Infrared detectors have many applications for detecting heat and enhancing night vision. Firefighters and rescue workers use thermal imaging cameras to see through smoke and debris to find hidden and trapped people that could not be found otherwise. It makes it easier to find the base of the fire. Technicians use it to see internal gaps in bridges and concrete, overheating in electrical equipment, thermal efficiency of buildings and appliances, and other thermal analyses. The military uses it to see people without being detected. Everyday uses include seeing sick people with elevated temperature, noticing faulty appliances, and awareness of people and animals in the dark. Modern infrared detectors are in goggles or handheld cameras. The goggles are large and heavy and limit the span of vision of the user. They are expensive, and high quality ones are excluded to military use. Researching and providing nanoscale infrared detectors applied directly to the eyes expand the availability and convenience of the device.

5 ENHANCED VISION - INFRARED 5 Literature Review Infrared frequencies have wavelengths longer than visible light, and cannot be seen by the human eye (Fieldhouse, N. M. et al. 2009). Some animals can see it by having a tapetum lucidum on the eye. Infrared radiation is emitted by warm objects; the frequency depends on the temperature. A major challenge in infrared detectors is the sensitivity and noise of the device. Charge coupled devices detect infrared wavelengths, and high quality ones only operate in cooled conditions, due to the heat created by the device. Nano- fabrication methods make it possible to create high sensitivity uncooled infrared detectors, with precise and low cost advantages. Microbolometers change resistance with temperature, and are used for thermal imaging (long- wavelength infrared). Vanadium oxide has a high temperature coefficient of resistivity, and high sensitivity. The material works at room temperature. Graphene photodetectors are used for its gapless band structure and ability to detect mid- infrared to ultraviolet (Liu, C., Chang Y., Norris, T., & Zhong, Z. 2014). In this project, they are used for detecting visible light in dim lighting, as they can amplify small photon energy into large electrical signal. They will also be used for detecting the mid- wavelength infrared to near- infrared range. They are as responsive as state- of- the- art mid- infrared detectors without needing cryogenic cooling. The performance of the infrared detector is similar to visible light detector, with high gain and response at room temperature. A team from the University of Washington created contact lenses with a single micro LED (Lingley, A. R. et al. 2011). They tested them on rabbits and it showed no adverse effects. This can advance to have several LEDs to create a full electronic display. They used wireless power through a transmitter. In this project, piezoelectric nanogenerators will be used for power as they rely on blinking rather than an external device. Infrared detectors and nanocontroller adjust brightness of LEDs (Wang, Z. L. & Song, J. 2006).

6 ENHANCED VISION - INFRARED 6 Project Description Since implanting nanoparticles within the brain is complicated and still in research, the infrared detector is put within contact lenses. Removable contact lenses are preferred over permanent lenses since infrared vision is not needed at all times. The graphene photodetector detects visible light and amplifies the signal. Graphene films are grown by chemical vapor deposition on copper foil then transferred to silicon/silicon oxide substrate. Graphene/tantalum pentoxide/graphene heterostructures are shaped through photolithography, graphene plasma etching, and metal lift- off. For detecting infrared, the tantalum pentoxide layer is replaced by intrinsic silicon. Graphene photodetector A pulse DC sputtering system deposits vanadium metal and oxygen to create vanadium oxide, which is used for detecting long- wavelength infrared. This is used as the IR absorbing material in the microbolometer. Microbolometer Each sensor has micro- LEDs next to it that would turn on when infrared is detected. The brightness of the LED increases when infrared signal is higher. Several of these would create a grid to

7 ENHANCED VISION - INFRARED 7 form a picture. Individual prisms for each LED would focus the LED light onto the retina (Mißfeldt, M. 2015). The sensors and LEDs are placed in front of the pupil, and due to the very small size of these components, they do not block the user's vision. All components would be powered by piezoelectric zinc oxide nanogenerators, where blinking would provide mechanical energy. They would be connected in series encircling the circumference of the lens. To enhance the signal, waveguides should be put in front of the sensor to direct photons/energy wavelengths to the sensor. Lower frequencies such as infrared would need bigger tubes, while higher frequencies use smaller tubes. Whenever the user blinks, the infrared signal would spike from the heat of the eyelids. A nanocontroller can detect repetitive movement of the piezoelectric generators when the user blinks and measure the infrared signal during that time to cancel out future signal spikes. The nanocontroller would use automatic gain control devices to adjust levels of brightness according to the amount of visible light and infrared detected. At night, the photodetectors allow more visible light. Near fires, they allow less visible light and more infrared in areas of smoke. Photolithography forms the circuit board. All components would be encased in hydrogel, which is used in normal contact lenses. Since the sensors operate at room temperature, the temperature of the eyes may be too high, so a material should protect the sensors if the hydrogel isn t enough. Depending on the use for the device, specific frequency ranges of infrared may be needed. Detecting a broad range of infrared limits the focus capability. Optical components made of quartz, CaF2, Ge and Si, polyethylene Fresnel lenses, and mirrors made of Al, Au or a similar material in front of the sensor can choose the specific frequency range (Jain, P. 2012). Different versions of the lenses can be adapted to different frequencies. Different intensities could also be shown in different colors. For instance, the base of a fire can be shown in red and surrounding heat shown in orange and yellow, while cooler objects are in grayscale. Active infrared uses an infrared source from laser or LED of infrared frequency to illuminate the environment so the sensor can better pick up signals. This creates a better image than thermal sensing. A helmet or hat would have the infrared lasers or LEDs and run on battery.

8 ENHANCED VISION - INFRARED 8 Different layers within contact lens have the wires for ground, positive, and the sensors. Piezoelectric generators go around the circumference of the lens. Layers are connected with nanowires. Piezoelectric generators power the ground and positive layers, which then power the sensors and other components.

9 ENHANCED VISION - INFRARED 9 Conclusions and Recommendations Infrared detecting contact lenses are a convenient and cheaper form of infrared detection. They are self powered and small in size. With the advancement of nanotechnology, sensitivity and size can be improved to create cheaper and more reliable devices. Further research and experimentation is needed to properly engineer this device. Precisely how many components are used, the range of frequencies needed for each application, how much the signals should be amplified, the size and composition of waveguides, the colors of the LEDs, the order the layers of the lenses should be organized, and additional components that may be needed to compensate the noise and power consumption of other components are all questions to be solved in lab.

10 ENHANCED VISION - INFRARED 10 References Fieldhouse, N. M. et al. (2009). Nanotechnology and Night Vision. Retrieved June 2, 2015 from vision- resouces/introduction. Jain, P. (2012). Infrared Sensors or IR Sensors. Retrieved June 4, 2015 from sensors#. Lingley, A. R. et al. (2011, 22 November). A single- pixel wireless contact lens display. Retrieved May 26, 2015 from Liu, C., Chang Y., Norris, T., & Zhong, Z. (2014, 16 March). Graphene photodetectors with ultra- broadband and high responsivity at room temperature. Nature Nanotechnology, 9, Retrieved May 28, 2015 from Mißfeldt, M. (2015). Google Glass (infographic) - How it works. Retrieved June 4, 2015 from sehhilfen.de/en/googleglass/. Wang, Z. L. & Song, J. (2006, 14 April). Piezoelectric Nanogenerators Based on Zinc Oxide Nanowire Arrays. Science, 312, Retrieved April 22, 2015 from