Zero-Power, Low-Noise Wireless Sensors and Integrated Systems
The Internet-of-Things (IoT) is a network comprising a massive number of physical objects, wireless sensors, and smart devices connected via the 5G communication infrastructures. Moreover, in the era of big-data and machine learning, sensor data could be manipulated by different techniques to infer various hidden information, such as the concept of Smart City. It is predicted that wirelessly networked sensors with not only high sensitivity, but also small size, low power and minimum cost (in fabrication, deployment and maintenance) will receive growing popularity in industrial, healthcare, automotive, and environmental applications. At UIC, we are dedicated to develop advanced wireless sensors with outstanding performance and benefits, including batteryless, low profile, ultrahigh sensitivity, and ultralow noise. We have proposed zero-power harmonic transponder sensors and the frequency-hopped spread spectrum (FHSS) pattern analysis (compatible to the C1Gen2 protocol) to realize long-range, high-precision wireless monitoring of macro/micro-scopic properties, with examples like smart contact lens, smart facemask, and wireless microfluidic sensors. Inspired by quantum mechanics, we have proposed and experimentally demonstrated the parity-time (PT)-symmetric non-Hermitian telemetering system that enables wireless interrogation of a passive microsensor with ultrahigh sensitivity and resolvability (Q-factor). This new sensor telemetry technique may be beneficial for many battery-free wireless wearables and bioimplants that are used for long-term, ambulatory monitoring of physiological parameters in human bodies, needed for managing chronic diseases (e.g. eye diseases, heart failure, or brain injury) to improve patients’ quality of life. In the future, we will continue to research advanced micro/nano-technological biosensors and ubiquitous telehealth/telemedicine technologies, with the aim to leverage the latest 5G/6G and mobile technologies to improve the overall quality of healthcare and reduce healthcare costs of the aging population.

Modern Antennas for 5G and Beyond (5GB)
The fifth-generation (5G) and beyond (5GB) wireless networks are largely expected to provide pervasive, high-speed and high-quality wireless coverage to meet societal and industrial needs. Moreover, integration of 5G networks with IoT may unleash future smart cities, industry 4.0, wireless health, vechicle-to-vechicle (V2V), and vechicle-to-everything (V2X) communications, namely a generalized ecosystem where networks can serve instantaneous connectivity for billions of connected devices. However, current antennas used in the 3G and 4G systems are often large, unsightly, and usually omnidirectional, which are no longer suitable in the  5G era. We are focused on innovative solutions to antenna design and RF systems to fullfill the 5G echosystems. The increasing demand of wireless modulus, along with aesthetics and cost, have driven us to study extremely miniaturized antennas and flexible, foldable and transparent antennas and “see-through” electromagnetric modulus, which can be embedded in windows, solar panels, sensors, wearable devices (e.g., smart contact lens), and display panels (antenna-on-display technology). We are also developing smart antennas that can produce directive and steerable radiation to reduce the effect of cochannel interference to basestation antennas, thus substantially increasing the capacity of wireless communication. We have investigated high-performance adapative beamformers based on low-profile metamaterials/metasurfaces apertures. The desired spatial signal processing can be accomplished by programming the pattern of activated meta-atoms. Unlike conventional phased array, this “meta-antenna” requires no costly phase shifters and can offer reasonable cost and reduced noise figure.

Nanoelectromagnetics: Plasmoncis and Nanophotonics
Plasmonics, tailoring light-matter interactions with surface plasmons at the nanoscale, is expected to improve photonic systems with enhanced efficiency and significant size down-scaling for CMOS compatibility. Particularly, localized surface plasmon resonances (LSPR), accompanied with the strong field enhancement in nanoantennas and optical metamaterials, can boost intrinsically weak optical responses, such as spontaneous emission and nonlinear wave mixing. In They may also be exploited to manipulate light emission and absorption, as well as resonant scattering at the nanoscale. We have reached an important milestone in the past decade. To date, we and collaborators have demonstrated that plasmonic nanostructures can enhance the Kerr biostability, second-harmonic generation (SHG), difference-frequency generation (DFG), phase conjugation, photon-assisted tunneling, and internal photoemission (hot-electron emission), with several orders of magnitude enhancement in conversion efficiency or quantum yields. We have also made contributions to 2D material nanophotonics. Prof. Chen’s visionary paper on “Atomically thin surface cloak using graphene monolayers” was among the first to originate the notion of graphene plasmonics with real-time tunability.

Electromagnetic/Acoustic/Elastic Wave Propagation and Scattering
Cloaking technology is widely hailed as a groundbreaking discovery in the field of metamaterials. A metamaterial/metasurface coverage with anomalously phased polarization may dramatically reduce the object visibility, due to the cancellation of scattering fields in all directions. The cloaking technology may enable not only invisibility and camouflaging, but also low-interference sensing and communication in light of remarkably suppressed crosstalks and interferences. Furthermore, combining passive metamaterial with non-Foster circuitry that shows a negatively differential reactance may make possible reduction of scattering cross-section over a broad range of frequencies. A cloaking device can also be designed to enhance the scattering and absorption of light, microwave, acoustic and elastic waves. For example, an electromagnetic cloak can enhance the non-radiative energy transfer and effectively couple the free space radiation to photodetectors and Joule nanoheaters (i.e. light management and trapping), and can improve the radiation efficiency and thus external quantum efficiency of emitters or  an electrically-small antenna. In the same vein, acoustic and elastic cloaks can be designed to reduce, cancel, or detour ultrasonic, biharmonic, water, thermal, and elastic waves hitting the object. Such protective cloaks can be exploited to against earthquakes and vibrations, and to open new vistas for maritime engineering.

Quantum Tunneling Devices and Their Applications
Quantum tunneling devices, such as vacuum microelectronic diodes/triodes and metal-insulator-metal (MIM) diodes, are commonly used in high power amplifiers and high-speed rectifiers at microwave and millimeter-wave frequencies owning to their ultrashort transit time (femtosecond timescale). Prof. Chen and his collaborators have been dedicated to study new device structures and materials  for improving performance of quantum tunneling devices, which include (1) nanomaterial emitters-based Spindt triodes and microwave distributed power amplifiers (e.g., carbon nanotubes and graphene flakes with a field enhancement factor of ~10⁴), and (2) 2D material-based MIM diodes with a zero-bias responsivity of 10 A/W; we have proposed a new class of ultrathin, atomically-flat 2-D transition-metal oxides that is converted from the 2D transition-metal dichalcogenide templates. We are working on efficient, low-threshold quantum tunneling devices for the next-generation microwave and even infrared rectification components (e.g., optical rectennas). We are also working on Ohmic contact engineering for 2D material-based field effect transistors and design of 2D/2D heterostructures that can effectively reduce the minimize the Schottky barrier height.

*Andrew Electromagnetics Laboratory
The UIC Andrew Electromagnetics Laboratory is shared among ECE faculty working on electromagnetism, high-frequency electronics, antennas, and wireless propagation. The lab is equipped with the state-of-the-art RF-to-microwave instruments and measurement facilities.
Web: https://andrew.lab.uic.edu/