Mehdi Hajizadegan

Toward transparent and self-activated graphene harmonic transponder sensors

We propose the concept and design of a transparent, flexible, and self-powered wireless sensor comprising a graphene-based sensor/frequency-modulator circuitry and a graphene antenna. In this all-graphene device, the multilayered-graphene antenna receives the fundamental tone at C band and retransmits the frequency-modulated sensed signal (harmonic tone) at X band. The frequency orthogonality between the received/re-transmitted signals may enable high-performance sensing in severe interference/clutter background. Here, a fully passive, quad-ring frequency multiplier is proposed using graphene field-effect transistors, of which the unique ambipolar charge transports render a frequency doubling effect with conversion gain being chemically sensitive to exposed gas/molecular/chemical/infectious agents. This transparent, light-weight, and self-powered system may potentially benefit a number of wireless sensing and diagnosis applications, particularly for smart contact lenses/glasses and microscope slides that ...

Self-powered and transparent all-graphene biosensor

We propose here the design and concept of self-powered wireless sensor based on the graphene radio-frequency (RF) components, which are transparent, flexible, and monolithically integrated on biocompatible soft substrate. This all-graphene wireless sensor consists of an optically transparent graphene antenna, which receives the fundamental tone and retransmits the sensed signal at its second harmonic, thus allowing low-noise sensing in a severe interference/clutter background. We show that a quad-ring circuit based on graphene transistors may simultaneously offer sensing and frequency modulation functions, with the nonlinear conversion gain being chemically sensitive to the gas/molecular/chemical exposures and agents. This battery-free and transparent sensors based on newly discovered 2D nanomaterials may benefit versatile wireless sensing and internet-of-things applications, such as smart contact lenses/glasses and microscope slides.

Hyperbolic metamaterial-based plasmoelectronic nanodevices for detection and harvesting of infrared radiation

Efficient conversion of long-wavelength light into direct current represents a great potential for photodetection, photocatalyst, and photovoltaics, with a variety of applications in sensing, security, defense, and emissive infrared energy harvesting. We propose here a new type of plasmo-electronic nanodevice, engineered as the hyperbolic metamaterial (HMM), to efficiently trap and nonlinearly rectify the incoming infrared radiation. These HMM-based nanodevices are constituted by the periodic, dissimilar metal-insulator-metal (MIM) heterojunctions, whose homogenized material properties enable the perfect absorption of infrared radiation and the localization of optical fields. The nonlinear optical rectification driven by the multiphoton-assisted tunneling in the MIM heterojunctions can efficiently convert the infrared radiation into the DC electricity (photocurrent). Most interestingly, the wideband or frequency-selective photon-to-electron conversion can be controlled via the design of HMM nanostructures. Our theoretical and numerical results demonstrate that the zero-bias responsivity of the HMM-based nanodevices can be up to ~100 mA/W in the mid-infrared regime.

A self-powered harmonic sensor based on simple graphene circuit and hybrid-fed antenna

We present a self-powered, low-profile harmonic sensor consisting of a frequency-modulated graphene sensor and a hybrid-fed circular patch antenna. We demonstrate that a fully-passive frequency modulator based on graphene transistors may achieve a chemically-sensitive frequency doubling effect, possible only with unique electronic properties of graphene. The nonlinear graphene sensor can be integrated with new types of compact hybrid-fed antenna for realizing continuous and power-efficient monitoring with wearable and implantable tags.

Graphene Sensing Modulator: Toward Low-Noise, Self-Powered Wireless Microsensors

We present here new types of self-powered, low-interference wireless sensors based on graphene circuits, which can have dual functions: chemical sensing at the molecular level and radio-frequency (RF) modulation. We demonstrate that a fully passive, graphene-based harmonic (transponder) sensor can display a chemically sensitive frequency multiplication effect, which, when linked to a hybrid-fed small antenna, can realize an ultrasensitive, low-profile, light-weight, and potentially flexible RF sensor. We have designed two different types of circuits comprising back-gate graphene field-effect transistors (GFETs) and compared in detail their performance and implementation complexity. We have also proposed a reliable readout method based on the machine learning for extracting the mean value and the fluctuation of chemical doping levels in GFETs. The proposed graphene-based harmonic sensor may potentially benefit a wide range of sensing applications, including, but not limited to, power-efficient, real-time monitoring of chemical/gas exposures and biological agents, as well as emerging wearable and implantable devices.

Efficient rectification of infrared radiation using nano-rectennas and slow-light microstructures

We discuss the possibility of rectifying infrared radiation using metal-insulator-metal (MIM) tunneling nanodiodes, which are nano-engineered to nano-rectennas and hyperbolic metamaterials (HMMs). We show that a lithographically patterned HMM may enable efficient, broadband and omnidirectional rectification of mid-infrared (MIR) in the slow-light mode, with responsivity much greater than conventional nano-rectennas. We demonstrate that the responsivity of HMM-based devices can reach few tens of mA/W in the MIR region, which may found many interesting applications in photodetection, infrared imaging, and energy harvesting.