Imaging Nanomechanical Vibrations and Manipulating Parametric Mode Coupling via Scanning Microwave Microscopy.

In this study, we present a novel platform based on scanning microwave microscopy for manipulating and detecting tiny vibrations of nanoelectromechanical resonators using a single metallic tip. The tip is placed on the top of a grounded silicon nitride membrane, acting as a movable top gate of the coupled resonator. We demonstrate its ability to map mechanical modes and investigate mechanical damping effects in a capacitive coupling scheme, based on its spatial resolution. We also manipulate the energy transfer coherently between the mode of the scanning tip and the underlying silicon nitride membrane, via parametric coupling. Typical features of optomechanics, such as anti-damping and electromechanically induced transparency, have been observed. Since the microwave optomechanical technology is fully compatible with quantum electronics and very low temperature conditions, it should provide a powerful tool for studying phonon tunnelling between two spatially separated vibrating elements, which could potentially be applied to quantum sensing.

Low Trapping Effects and High Electron Confinement in Short AlN/GaN-On-SiC HEMTs by Means of a Thin AlGaN Back Barrier.

In this paper, we report on an enhancement of mm-wave power performances with a vertically scaled AlN/GaN heterostructure. An AlGaN back barrier is introduced underneath a non-intentionally doped GaN channel layer, enabling the prevention of punch-through effects and related drain leakage current under a high electric field while using a moderate carbon concentration into the buffer. By carefully tuning the Al concentration into the back barrier layer, the optimized heterostructure offers a unique combination of electron confinement and low trapping effects up to high drain bias for a gate length as short as 100 nm. Consequently, pulsed (CW) Load-Pull measurements at 40 GHz revealed outstanding performances with a record power-added efficiency of 70% (66%) under high output power density at VDS = 20 V. These results demonstrate the interest of this approach for future millimeter-wave applications.

Effects of stochastic forces on the nonlinear behaviour of a silicon nitride membrane nanoelectromechanical resonator.

In this work, we present the effects of stochastic force generated by white noise on the nonlinear dynamics of a circular silicon nitride membrane. By tuning the membrane to the Duffing nonlinear region, detected signals switching between low- and high-amplitudes have been observed. They are generated by noise-assisted random jumps between bistable states at room temperature and exhibit high sensitivity to the driving frequency. Through artificially heating different mechanical vibration modes by external input of white noise, the switching rate exhibits exponential dependence on the effective temperature and follows with Kramer's law. Furthermore, both the measured switching rate and activation energy exhibit sensitivity to the width of the hysteresis window in nonlinear response and the driving force, which is in qualitative agreement with the theoretical descriptions. Besides, white noise-induced hysteresis window squeezing and bifurcation point shifting have also been observed, which are attributed to the stochastic force modulation of the spring constant of the membrane. These studies are carried out in an all-electric operating scheme at room temperature, paving the way for the exploration of probability distribution-based functional elements that can be massively integrated on-chip.

Coupling Capacitively Distinct Mechanical Resonators for Room-Temperature Phonon-Cavity Electromechanics.

Coupled electromechanical resonators that can be independently driven/detected and easily integrated with external circuits are essential for exploring mechanical modes based signal processing and multifunctional integration. One of the main challenges lies in controlling energy transfers between distinct resonators experiencing nanoscale displacements. Here, we present a room temperature electromechanical system that mimics a "phonon-cavity", in analogy with optomechanics. It consists in a silicon nitride membrane capacitively coupled to an aluminum drum-head resonator. We demonstrate electromechanically induced transparency and amplification through manipulating the mechanical displacements of this coupled system, creating interferences in the measured signal. The anti-damping effects, generated by phonon-cavity force, have been observed in both movable objects. We develop an analytical model that captures the analoguous optomechanical features in the classical limit and enables to fit quantitatively the measurements. Our results open up new possibilities for building compact and multifunctional mechanical systems, and exploring phonon-phonon coupling based optomechanics.

High-Q Silicon Nitride Drum Resonators Strongly Coupled to Gates.

Silicon nitride (SiN) mechanical resonators with high quality mechanical properties are attractive for fundamental research and applications. However, it is challenging to maintain these mechanical properties while achieving strong coupling to an electrical circuit for efficient on-chip integration. Here, we present a SiN drum resonator covered with an aluminum thin film, enabling large capacitive coupling to a suspended top-gate. Implementing the full electrical measurement scheme, we demonstrate a high quality factor ∼104 (comparable to that of bare drums at room temperature) and present our ability to detect ∼10 mechanical modes at low temperature. The drum resonator is also coupled to a microwave cavity, so that we can perform optomechanical sideband pumping with a fairly good coupling strength G and demonstrate mechanical parametric amplification. This SiN drum resonator design provides efficient electrical integration and exhibits promising features for exploring mode coupling and signal processing.

Step-by-Step Protocol for Superparamagnetic Nanoparticle-Based Plasma Membrane Isolation from Eukaryotic Cell.

Here, we elaborate our detailed protocol for synthesis, functionalization, and application of superparamagnetic nanoparticle (SPMNP) for plasma membrane and lysosome isolation. We used standard thermal decomposition-based synthesis of iron oxide (Fe3O4) core SPMNP 1.0. Using ligand addition methodology, we surface functionalized SPMNP 1.0 with phospholipids and generated phospholipid-SPMNP 2.0. Further we used NH2-phospholipid-SPMNP 2.0 to isolate plasma membrane. Using our SPMNP subcellular fractionation protocol, we are able to isolate high-pure-high-yield plasma membrane using NH2-phospholipid-SPMNP 2.0. As a future perspective, we propose to use SPMNP on clinical patient samples and perform mass spectrometry-based proteomics, lipidomics, and glycomics for early cancer diagnosis.

Step-by-Step Protocol for Superparamagnetic Nanoparticle-Based Endosome and Lysosome Isolation from Eukaryotic Cell.

Here, we report our step-by-step protocol for superparamagnetic nanoparticle (SPMNP)-based endosome and lysosome isolation from HeLa. Briefly, we synthesized SPMNP 1.0 with iron oxide (Fe3O4) core using thermal decomposition method. Further, we performed ligand-exchange strategy for surface functionalization of SPMNP 1.0 with dimercaptosuccinic acid (DMSA). Thus, we generated DMSA-SPMNP 2.0 and used DMSA-SPMNP 2.0 to isolate endosomes and lysosome from HeLa cells. Using our SPMNP subcellular fractionation protocol, we are able to isolate high-pure-high-yield lysosomes using DMSA-SPMNP 2.0 for lysosome proteomics and lipidomics in order to better understand subcellular compartments.

Synthesis of Hybrid Gold Nanoparticle (AuNP) Functionalized Superparamagnetic Nanoparticles (SPMNPs) for Efficient Coupling of Biomolecules.

Recently, we reported our methodology for isolating plasma membrane and lysosome from eukaryotic cell using superparamagnetic nanoparticles (SPMNPs). Here in this article, we report a step-by-step protocol for synthesis of hybrid gold nanoparticle (AuNP), surface functionalization of AuNPs on superparamagnetic nanoparticles (SPMNPs), and potential use of hybrid AuNP-SPMNP for efficient coupling of biomolecules.

BacMam System for Rapid Recombinant Protein Expression in Mammalian Cells.

Baculovirus expression vector system (BEVS) is an established technology for recombinant protein expression in insect cells. Further, BEVS-mediated gene transduction of mammalian cells (BacMam) is emerging as a technique for high level recombinant protein expression in mammalian cells. Here, we describe generic method in using BEVS as a BacMam for rapid recombinant protein expression in mammalian cells.