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Piezoelectric actuators transform electrical energy into mechanical energy, and because of their compactness, quick response time and accurate displacement, they are sought after in many applications. Polycrystalline piezoelectric ceramics are technologically more appealing than single crystals due to their simpler and less expensive processing, but have yet to display electrostrain values that exceed 1%. Here we report a material design strategy wherein the efficient switching of ferroelectric–ferroelastic domains by an electric field is exploited to achieve a high electrostrain value of 1.3% in a pseudo-ternary ferroelectric alloy system, BiFeO3–PbTiO3–LaFeO3. Detailed structural investigations reveal that this electrostrain is associated with a combination of several factors: a large spontaneous lattice strain of the piezoelectric phase, domain miniaturization, a low-symmetry ferroelectric phase and a very large reverse switching of the non-180° domains. This insight for the design of a new class of polycrystalline piezoceramics with high electrostrains may be useful to develop alternatives to costly single-crystal actuators.

mRNA vaccines have been demonstrated as a powerful alternative to traditional conventional vaccines because of their high potency, safety and efficacy, capacity for rapid clinical development, and potential for rapid, low-cost manufacturing. These vaccines have progressed from being a mere curiosity to emerging as COVID-19 pandemic vaccine front-runners. The advancements in the field of nanotechnology for developing delivery vehicles for mRNA vaccines are highly significant. In this review we have summarized each and every aspect of the mRNA vaccine. The article describes the mRNA structure, its pharmacological function of immunity induction, lipid nanoparticles (LNPs), and the upstream, downstream, and formulation process of mRNA vaccine manufacturing. Additionally, mRNA vaccines in clinical trials are also described. A deep dive into the future perspectives of mRNA vaccines, such as its freeze-drying, delivery systems, and LNPs targeting antigen-presenting cells and dendritic cells, are also summarized.

Droplet encapsulations using liquid or solid shells are of significant interest in microreactors, drug delivery, crystallization, and cell growth applications. Despite progress in droplet-related technologies, tuning micron-scale shell thickness over a large range of droplet sizes is still a major challenge. In this work, we report capillary force assisted cloaking using hydrophobic colloidal particles and liquid-infused surfaces. The technique produces uniform solid and liquid shell encapsulations over a broad range (5–200 μm shell thickness for droplet volume spanning over four orders of magnitude). Tunable liquid encapsulation is shown to reduce the evaporation rate of droplets by up to 200 times with a wide tunability in lifetime (1.5 h to 12 days). Further, we propose using the technique for single crystals and cell/spheroid culture platforms. Stimuli-responsive solid shells show hermetic encapsulation with tunable strength and dissolution time. Moreover, scalability, and versatility of the technique is demonstrated for on-chip applications. Encapsulated liquids are important for several microreactor applications, including (bio)chemistry in confined spaces. Here, the authors report on oil-infused particle shells that allow control of shell thickness, stability, and permeability for applications in crystal growth and cell cultivation.

Crystal–amorphous transformation achieved via the melt-quench pathway in phase-change memory involves fundamentally inefficient energy conversion events; and this translates to large switching current densities, responsible for chemical segregation and device degradation. Alternatively, introducing defects in the crystalline phase can engineer carrier localization effects enhancing carrier–lattice coupling; and this can efficiently extract work required to introduce bond distortions necessary for amorphization from input electrical energy. Here, by pre-inducing extended defects and thus carrier localization effects in crystalline GeTe via high-energy ion irradiation, we show tremendous improvement in amorphization current densities (0.13–0.6 MA cm −2 ) compared with the melt-quench strategy (∼50 MA cm −2 ). We show scaling behaviour and good reversibility on these devices, and explore several intermediate resistance states that are accessible during both amorphization and recrystallization pathways. Existence of multiple resistance states, along with ultralow-power switching and scaling capabilities, makes this approach promising in context of low-power memory and neuromorphic computation. Phase change memories involve crystalline-to-amorphous transformations which require high current densities. Here, the authors introduce extended defects in GeTe crystals, reduce the current densities necessary for amorphization and obtain low-power, scalable memories with multiple resistance states.

In this study, we report the fabrication of a cubic phase SnO 2 -based thin film gas sensor with excellent sensitivity and selectivity for carbon monoxide (CO) gas at room temperature, with a high response of 25606% achieved at 2 ppm CO gas concentration, and a detection limit down to 1 ppb. Cubic phase SnO 2 thin films are synthesized using a simple sol-gel process, followed by spin coating. Our synthesis technique allows for stabilizing the cubic phase of SnO 2 , confirmed through XRD and TEM studies, which is otherwise reported at high pressures and temperatures. Further, our DFT simulations show that the cubic phase of SnO 2 nanoparticles has a lower energy barrier for CO adsorption and desorption than the more common tetragonal phase. The low-voltage and ambient operating conditions of the sensor reported in this study make it highly practical for widespread use, thus offering a promising solution to the growing need for efficient and affordable gas sensing applications, including environmental monitoring, industrial safety, and medical diagnosis. This study presents a cubic phase SnO 2 thin film gas sensor with ultra-high CO sensitivity and 1 ppb detection limit, enabled by sol-gel synthesis and DFT insights, offering practical low-voltage sensing for diverse applications.

This paper presents a cryogenic analysis of Junction less Under lapped Nanowire MOSFETs in lower technology nodes. The temperature dependent analysis is carried out to extract the DC figure of merits (FOMs) of the proposed nanowire MOSFET. The analysis is carried out to investigate the drain current associated with the device at different temperature. Further the analysis is extended with underlap length variation from source, drain and both sides. As the trans conductance plays a vital role in device performance estimation, so the analysis is further extended to calculate the transconductance for all the temperature variation and underlap length variation. With the introduction of gate metal under lapping, the sub-threshold behaviour of the proposed structure under different temperature is carried out extensively.

Correlated electron materials (CEMs) host a rich variety of condensed matter phases. Vanadium dioxide (VO 2 ) is a prototypical CEM with a temperature-dependent metal-to-insulator (MIT) transition with a concomitant crystal symmetry change. External control of MIT in VO 2 —especially without inducing structural changes—has been a long-standing challenge. In this work, we design and synthesize modulation-doped VO 2 -based thin film heterostructures that closely emulate a textbook example of filling control in a correlated electron insulator. Using a combination of charge transport, hard X-ray photoelectron spectroscopy, and structural characterization, we show that the insulating state can be doped to achieve carrier densities greater than 5 × 10 21  cm −3 without inducing any measurable structural changes. We find that the MIT temperature (T MIT ) continuously decreases with increasing carrier concentration. Remarkably, the insulating state is robust even at doping concentrations as high as ~0.2 e − /vanadium. Finally, our work reveals modulation-doping as a viable method for electronic control of phase transitions in correlated electron oxides with the potential for use in future devices based on electric-field controlled phase transitions. The metal-insulator transition in VO2 is concomitant with the structural transition, making purely electrical control challenging. Here the authors use a modulation-doped heterostructure to demonstrate modulation of the transition temperature with doping, without introducing structural changes.

Germanium telluride (GeTe) is both polar and metallic, an unusual combination of properties in any material system. The large concentration of free-carriers in GeTe precludes the coupling of external electric field with internal polarization, rendering it ineffective for conventional ferroelectric applications and polarization switching. Here we investigate alternate ways of coupling the polar domains in GeTe to external electrical stimuli through optical second harmonic generation polarimetry and in situ TEM electrical testing on single-crystalline GeTe nanowires. We show that anti-phase boundaries, created from current pulses (heat shocks), invert the polarization of selective domains resulting in reorganization of certain 71 o domain boundaries into 109 o boundaries. These boundaries subsequently interact and evolve with the partial dislocations, which migrate from domain to domain with the carrier-wind force (electrical current). This work suggests that current pulses and carrier-wind force could be external stimuli for domain engineering in ferroelectrics with significant current leakage. Polar metals such as GeTe could store information using electric domains but the high conductivity screens electric fields, preventing the use of usual domain control techniques. Here, the authors demonstrate that polar domains in GeTe can be manipulated using electrically generated heat shocks.

Phase-change materials undergo rapid and reversible crystalline-to-amorphous structural transformation and are being used for nonvolatile memory devices. However, the transformation mechanism remains poorly understood. We have studied the effect of electrical pulses on the crystalline-to-amorphous phase change in a single-crystalline Ge₂Sb₂Te₂ (GST) nanowire memory device by in situ transmission electron microscopy. We show that electrical pulses produce dislocations in crystalline GST, which become mobile and glide in the direction of hole-carrier motion. The continuous increase in the density of dislocations moving unidirectionally in the material leads to dislocation jamming, which eventually induces the crystalline-to-amorphous phase change with a sharp interface spanning the entire nanowire cross section. The dislocation-templated amorphization explains the large on/off resistance ratio of the device.