New sensors for simultaneous achievement of a continuous temperature sensing and threshold temperature sensing in the same device
Institute Reference: INV-20086
As wireless sensing and monitoring has continued to play an increasingly pivotal role in a variety of applications, a strong need has developed for scalable, low power/zero power systems with long range and high sensitivity.
Recently, much attention has been paid to the development of compact and passive radio-frequency (RF) transponders. This has been driven by the growing need to protect specialized equipment, such as those used in manufacturing warehouses and data-centers from undesired increases in their operational temperature. Similarly, the availability of such RF systems can also be beneficial in cold-chain applications where passive temperature-threshold systems can enable the prompt identification of any perishables suddenly exposed to incompatible temperatures, such as food or medicine. While different types of passive transponders that enable either continuous or threshold‑temperature‑sensing have been demonstrated, none of them can address both functionalities and have design characteristics that enable the monitoring of thousands of different items. Additionally, existing passive sensing systems have limitations on range, sensitivity, and scalability.
Northeastern researchers are developing multiple passive sensing architectures to address this critical need. The first architecture leverages the unique dynamical characteristics of parametric solid-state components and acoustic resonators to achieve sensing systems that surpass, by orders of magnitude, the sensitivity achieved by conventional linear sensing components and devices. It is able to achieve continuous and threshold sensing, for a variety of applications. This system allows for real-time identification and a massive simultaneous sensing of a large number of items and systems. Unlike any other systems demonstrated to date, it relies on the combination of a high-Q resonant component included in the output port of a parametric frequency divider. By simultaneously leveraging the unique properties of both systems, these devices are able to outperform previously developed systems by orders of magnitude.
A second architecture under development involves a highly-miniaturized (< 1cm2) and battery-less Ultra-High-Frequency (UHF) tag, namely the Aluminum Scandium Nitride (AlScN) Sub-Harmonic Tag (Sub-HT). These UHF tags enable the remote identification of items at extraordinarily long distances from a reader, without requiring any integrated RF harvesters, who’s low efficiencies often prevent long-range operation. The AlScN Sub-HT leverages the unique features and compact form-factor of Aluminum Scandium Nitride (AlScN) microacoustic resonators and ferroelectric varactors, along with the recently unveiled parametric dynamics of subharmonic tags. These tags are able to respond to ultra-low power (< -50 dBm) UHF signatures through the passive generation and radiation of sub-harmonic signals of the interrogating ones. It has ranges higher than 20 meters and is only limited by the power sensitivity of the readers. Alternatively, the proposed Sub-HT can be interfaced with any printed UHF RFID antennas to grant detection ranges that can exceed 200 meters while maintaining the same form factor of the available UHF tags.