Zero standby power crop water-stress detector leading to the optimization of water usage and yield.

Agricultural sensors are powerful tools to optimize crop productivity while conserving natural resources. Here we report a crop water-stress detector based on a plasmonically-enhanced micromechanical photoswitch capable of detecting water content in leaves that is lower than a predetermined threshold without consuming electrical power when the leaf is healthy. The detection mechanism exploits the energy in a specific narrow-spectral band of solar radiation reflected off leaves that is strongly correlated to the water content in plants.

Curvature and Stress Effects on the Performance of Contour-Mode Resonant ΔE Effect Magnetometers.

Miniaturized piezoelectric/magnetostrictive contour-mode resonators have been shown to be effective magnetometers by exploiting the ΔE effect. With dimensions of ~100-200 μm across and <1 μm thick, they offer high spatial resolution, portability, low power consumption, and low cost. However, a thorough understanding of the magnetic material behavior in these devices has been lacking, hindering performance optimization.

Zero-power infrared digitizers based on plasmonically enhanced micromechanical photoswitches.

State-of-the-art sensors use active electronics to detect and discriminate light, sound, vibration and other signals. They consume power constantly, even when there is no relevant data to be detected, which limits their lifetime and results in high costs of deployment and maintenance for unattended sensor networks. Here we propose a device concept that fundamentally breaks this paradigm-the sensors remain dormant with near-zero power consumption until awakened by a specific physical signature associated with an event of interest.

Acoustically actuated ultra-compact NEMS magnetoelectric antennas.

State-of-the-art compact antennas rely on electromagnetic wave resonance, which leads to antenna sizes that are comparable to the electromagnetic wavelength. As a result, antennas typically have a size greater than one-tenth of the wavelength, and further miniaturization of antennas has been an open challenge for decades. Here we report on acoustically actuated nanomechanical magnetoelectric (ME) antennas with a suspended ferromagnetic/piezoelectric thin-film heterostructure.

Graphene-aluminum nitride NEMS resonant infrared detector.

The use of micro-/nanoelectromechanical resonators for the room temperature detection of electromagnetic radiation at infrared frequencies has recently been investigated, showing thermal detection capabilities that could potentially outperform conventional microbolometers. The scaling of the device thickness in the nanometer range and the achievement of high infrared absorption in such a subwavelength thickness, without sacrificing the electromechanical performance, are the two key challenges for the implementation of fast, high-resolution micro-/nanoelectromechanical resonant infrared detectors. In this paper, we show that by using a virtually massless, high-electrical-conductivity, and transparent graphene electrode, floating at the van der Waals separation of a few angstroms from a piezoelectric aluminum nitride nanoplate, it is possible to implement ultrathin (460 nm) piezoelectric nanomechanical resonant structures with improved electromechanical performance (>50% improved frequency×quality factor) and infrared detection capabilities (>100× improved infrared absorptance) compared with metal-electrode counterparts, despite their reduced volumes.

Plasmonic piezoelectric nanomechanical resonator for spectrally selective infrared sensing.

Ultrathin plasmonic metasurfaces have proven their ability to control and manipulate light at unprecedented levels, leading to exciting optical functionalities and applications. Although to date metasurfaces have mainly been investigated from an electromagnetic perspective, their ultrathin nature may also provide novel and useful mechanical properties. Here we propose a thin piezoelectric plasmonic metasurface forming the resonant body of a nanomechanical resonator with simultaneously tailored optical and electromechanical properties.

Effects of a multichannel dynamic functional electrical stimulation system on hemiplegic gait and muscle forces.

[Purpose] The purpose of the study was to design and implement a multichannel dynamic functional electrical stimulation system and investigate acute effects of functional electrical stimulation of the tibialis anterior and rectus femoris on ankle and knee sagittal-plane kinematics and related muscle forces of hemiplegic gait. [Subjects and Methods] A multichannel dynamic electrical stimulation system was developed with 8-channel low frequency current generators. Eight male hemiplegic patients were trained for 4 weeks with electric stimulation of the tibia anterior and rectus femoris muscles during walking, which was coupled with active contraction.

Graphene as a Massless Electrode for Ultrahigh-Frequency Piezoelectric Nanoelectromechanical Systems.

Designing "ideal electrodes" that simultaneously guarantee low mechanical damping and electrical loss as well as high electromechanical coupling in ultralow-volume piezoelectric nanomechanical structures can be considered to be a key challenge in the NEMS field. We show that mechanically transferred graphene, floating at van der Waals proximity, closely mimics "ideal electrodes" for ultrahigh frequency (0.2 GHz < f0 < 2.