Nature Electronics最新文献

Integrated circuits based on two-dimensional semiconductors require ultrathin gate insulators that can provide high interface quality and dielectric reliability, minimized electrically active traps and efficient gate controllability. However, existing two-dimensional insulators do not provide a good trade-off in terms of bandgap, breakdown strength, dielectric constant, leakage current and bias temperature stability. Here, we show that single crystals of magnesium niobate (MgNb₂O₆) can be obtained through a buffer-controlled epitaxial growth process on a mica substrate. The atomically thin MgNb₂O₆ crystals have a wide bandgap (around 5.0 eV), high dielectric constant (around 20), large breakdown voltage (around 16 MV cm⁻¹) and good thermal reliability. The MgNb₂O₆ can form a van der Waals interface with monolayer molybdenum disulfide (MoS₂) with an extremely low density of trap states. MoS₂ field-effect transistors with MgNb₂O₆ gate dielectrics exhibit a hysteresis under 0.9 mV (MV cm⁻¹)⁻¹, a subthreshold swing of 62 mV dec⁻¹, an on/off current ratio of up to 4 × 10⁷ and high electrical reliability at 500 K. The excellent electrostatic controllability of MgNb₂O₆ allowed us to create graphene-contacted transistors and inverter circuits with a channel length of 50 nm.

The researchers — who are based at the German Aerospace Center and Technical University of Munich — created a mechatronic design for sensing redundancy, where the number of sensor measurements exceeds the number of possible motions of the robotic arm, and combined it with a momentum-based monitoring method to provide the arm with an intrinsic sense of touch across its surface. Two force-torque sensors, one in the base and one in the wrist, and four torque sensors in the joints provide 16 measurements. The robot could recognize letters and digits traced directly on its structure, and the team also created virtual buttons that could be placed at different locations across the arm and assigned different functions.

Original reference: Sci. Robot. 9, eadn4008 (2024)

Each sensor consists of multiple micro-strain gauges containing a stressed layer of silicon dioxide that, after the stress is released by dissolving a sacrificial layer, deforms into a three-dimensional geometry. Thin metal or alloy wires on the strain gauges can measure normal force, shear force and temperature. Because the sensors are made by standard processes used in microelectromechanical system fabrication, the researchers — who are based at Peking University, North China University of Technology, the Chinese Academy of Medical Sciences, and Peking University Third Hospital — can manufacture them in large arrays on a four-inch silicon wafer. These can then be separately detached and placed on different substrates, such as a flexible printed circuit board, to achieve the desired sensor distribution and density.

Original reference: Sci. Adv. 10, eadp6094 (2024)

The researchers — who are based at the Institute of Metal Research in Shenyang China, the University of Science and Technology of China, Peking University and the Shenzhen Institute of Advanced Technology — fabricated micrometre-scale devices using a p-type germanium substrate as the current collector and two separate monolayer graphene emitter and base layers placed on top. Under bias, stimulated emission leads to an increase in the collector current and the transistors exhibited subthreshold swing values as low as 0.38 mV dec⁻¹ and on-currents of 165.2 μA μm⁻¹. Negative differential resistance behaviour with peak-to-valley current ratios of approximately 100 was possible at room temperature. This behaviour was also used to create multi-valued logic gates with reconfigurable logic.

Original reference: Nature 632, 782–787 (2024)

Computational spectrometers with small footprints can be integrated with other devices for use in applications such as chemical analysis, medical diagnosis and environmental monitoring. However, their spectral resolution is limited because conventional photoelectric detectors only measure an amplitude-dependent response to incident light. Here we show that a deformable two-dimensional homojunction can be used to create a microspectrometer with dual-signal spectral reconstruction. The semifloating molybdenum disulfide homojunction exhibits a giant electrostriction effect through which the kinetics of photo-generated carriers can be manipulated via an in-plane electric field generated by gate voltage. By leveraging the tunability of both amplitude and relaxation time of the photoelectric response, a dual-signal response can be used with a deep neural network algorithm to reconstruct an incident spectrum. Our dual-signal microspectrometer has a footprint of 20 × 25 µm², offers a resolution of 1.2 nm and has a spectral waveband number of 380, which is comparable to benchtop spectrometers.

Transcranial focused ultrasound has shown promising non-invasive therapeutic effects for drug-resistant epilepsy due to its spatial resolution and depth penetrability. However, current manual strategies, which use fixed neurostimulation protocols, cannot provide precise patient-specific treatment due to the absence of ultrasound wave-insensitive closed-loop neurostimulation devices. Here, we report a shape-morphing cortex-adhesive sensor for closed-loop transcranial ultrasound neurostimulation. The sensor consists of a catechol-conjugated alginate hydrogel adhesive, a stretchable 16-channel electrode array and a viscoplastic self-healing polymeric substrate, and is coupled to a pulse-controlled transcranial focused ultrasound device. It can provide conformal and robust fixation to curvy cortical surfaces, and we show that it is capable of stable neural signal recording in awake seizure rodents during transcranial focused ultrasound neurostimulation. The sensing performance allows real-time detection of preseizure signals with unexpected and irregular high-frequency oscillations, and we demonstrate closed-loop seizure control supervised by intact cortical activity under ultrasound stimulation in awake rodents.

Wearable health monitoring platforms require advanced sensing modalities with integrated electronics. However, current systems suffer from limitations related to energy supply, sensing capabilities, circuitry regulations and large form factors. Here, we report an autonomous and continuous sweat sensing system that operates on a fingertip. The system uses a self-voltage-regulated wearable microgrid based on enzymatic biofuel cells and AgCl-Zn batteries to harvest and store bioenergy from sweat, respectively. It relies on osmosis to continuously supply sweat to the sensor array for on-demand multi-metabolite sensing and is combined with low-power electronics for signal acquisition and wireless data transmission. The wearable system is powered solely by fingertip perspiration and can detect glucose, vitamin C, lactate and levodopa over extended periods of time.

Organic electrochemical transistors can be used in wearable sensors to amplify biological signals. Other wireless communication systems are required for applications in continuous health monitoring. However, conventional wireless communication circuits, which are based on inorganic integrated chips, face limitations in terms of conformability due to the thick and rigid integrated circuit chips. Here, we report an ultrathin organic–inorganic device for wireless optical monitoring of biomarkers, such as glucose in sweat and glucose, lactate and pH in phosphate-buffered saline. The conformable system integrates an organic electrochemical transistor and a near-infrared inorganic micro-light-emitting diode on a thin parylene substrate. The device has an overall thickness of 4 μm. The channel current of the transistor changes according to the biomarker concentration, which alters the irradiance from the light-emitting diode to enable biomarker monitoring. We combine the device with an elastomeric battery circuit to create a wearable patch. We also show that the system can be used for near-infrared image analysis.