Cost-effective, miniaturized switch-based detection method with integrated measurement functionality
Institute Reference: INV-21097
Battery-powered wireless sensors are of particular interest in sensor networks and internet of things (IoT) applications owing to their ability to be deployed anywhere without the need for any wiring. This is especially valuable in applications that require placement in hard-to-reach or hazardous areas. Significant advances in nanotechnology and microelectromechanical systems (MEMS) sensors have resulted in the development of sensors with low size, weight, and power (SWaP) which are critical for long-term remote deployment. However, state-of-the-art sensors are still either duty-cycled or actively scan the environment continuously for a signal of interest, ultimately limiting their lifetime.
Recently, a new class of sensors called ‘near-zero power’ sensors was developed to overcome this limitation by utilizing the energy in the sensed signal itself to perform its detection. These sensors are therefore event-driven and are always alert to the target signal to be detected (i.e., 100% duty cycle). However, this approach increases circuit complexity, cost, and size especially for IR detectors (such as pyroelectric ones) and filters at mid-IR wavelengths.
This Northeastern invention is the first ultra-low power infrared (IR) wireless sensor based on an IR micromechanical photoswitch (MP) and a microcontroller capable of quantifying the above-threshold input IR radiation and transmitting the measured value wirelessly. The entire sensor node remains asleep (standby power ~811 nW) until awakened by the always-alert IR digitizer (i.e., the MP) upon exposure to targeted IR radiation.
Unlike existing switch-based zero power sensors that only provide a binary output (i.e., indicate the presence of an IR source), the awakened sensor exploits a thermally-modulated electromechanical pull-in mechanism to measure the incident IR power using the same MP, the value of which is then transmitted wirelessly to a remote gateway.
It is worth noting that the voltage-based sweep (the key idea for the invention) can be used in any other application that uses switches that undergo displacement upon exposure to the targeted input signal. It can also be used in duty-cycled applications that do no require low standby power consumption.