Maryam Sakhdari

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 ...

Transparent and self-activated harmonic sensor using integrated graphene antennas and circuits

We propose a new paradigm of transparent, flexible, and self-powered radio-frequency (RF) harmonic sensor based on all-graphene antenna and frequency multiplier/sensor. The multilayered-graphene antenna receives fundamental tone at C band and retransmits the sensed signal (harmonic tone) at X band, thus allowing high-performance sensing in a severe interference/clutter background. The frequency multiplier is built by graphene transistors, with the conversion gain being chemically sensitive to exposed gas/molecule/chemical dopants. This all-graphene system may benefit various wireless sensing applications, such as smart contact lens and microscope slides.

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.

Ultrasensitive telemetric sensor based on adapted parity-time symmetry

We propose and experimentally investigate a new parity-time (PT)-symmetric wireless sensor system, whose equivalent circuit topologically satisfies the time-reversal and spatial-inversion symmetry. We demonstrate that an adapted PT-symmetric wireless sensor can enable high quality-factor (Q-factor) and great sensitivity in detecting physiological and environmental variations, overcoming the long-standing challenge in optimizations of Q-factor and sensitivity of miniature wireless sensors. Our results may ever have an impact on many wireless sensing, imaging and monitoring systems, particularly benefiting the emerging micromachined sensors, bioimplants, wearable devices, and internet-of-things applications.

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.