electrical and electronics
Printable IoT sensor development platform
Advances in additive manufacturing have enabled development of printable electronic sensor elements that can be deposited onto flexible substrates. To benchmark performance of printed sensors against the state of the art, NASA developed a low power flexible sensor platform. The platform integrates the following key components and features: -Flexible substrate: DuPont Kapton allows bending around cylindrical surfaces as small as in diameter. -Embedded microcontroller: Cypress CY8C4248 LQI-BL583 Arm Cortex M0 processor with BLE wireless controller, max frequency 48 MHz. Supports low power modes of operation, capacitive sensing support, and a single-channel 12-bit AD converter. -Commercial sensor suite: Bosch BNO080 inertial sensor; Bosch BME280 humidity, pressure, and temperature sensor; AMS CCS811 air quality sensor (VOCs and CO2). -Prototyping area for custom-printed sensors: 1) thermistor, uses carbon-based PTC resistor paste DuPont2792; 2) capacitive humidity sensor using a NASA-developed dielectric ink. NASA researchers have used the platform to study performance of the printed capacitive humidity sensor. The 2x4 mm co-doped barium titanate sensing element is highly sensitive to water vapor and performs as an unobtrusive breathing monitor, sensitive to breath at distances of up to 20 cm. Average change of sensor capacitance at a distance of 7.5 cm was observed to be 6.23.5 pF.
Optical De-Multiplexing Method for QKD Encryption
Classical laser communication gimbals are coupled to 105um multimodal receiving fibers for the high-power transmission of data, fine pointing, and tracking. These fibers cannot be used in free space optical communication applications using Quantum Key Distribution (QKD) since polarization state information encoded by QKD photons is not retained. To accommodate low energy QKD photons and high energy data streams necessary for encryption of optical links, the inventor adopted a space-and-wave (SAW) division de-multiplexing approach. The SAW division method uses a double clad fiber with a 9um core and a 105um 1st cladding. This arrangement captures 1590nm wavelength QKD photons in the core channel and a 1555.75nm wavelength data channel in the 1st cladding. By defining wavelength separation between 30-40nm, a single focusing lens can be used to focus only one wavelength to a diffraction limited spot (see figures included). Using this method, a QKD channel is focused to a diffraction limited spot on the 9um core of the double clad fiber. The chosen wavelength separation generates a defocused diffraction pattern with a hollow center, and with remaining optical power in concentric rings outside of the 9um core, yet inside the 105um core. The QKD signal is directed into the 9um core, and the data channel is coupled into the 105um secondary core for traditional data demodulation.