Multilevel design and construction in nanomembrane rolling for three-dimensional angle-sensitive photodetection.

Releasing pre-strained two-dimensional nanomembranes to assemble on-chip three-dimensional devices is crucial for upcoming advanced electronic and optoelectronic applications. However, the release process is affected by many unclear factors, hindering the transition from laboratory to industrial applications. Here, we propose a quasistatic multilevel finite element modeling to assemble three-dimensional structures from two-dimensional nanomembranes and offer verification results by various bilayer nanomembranes. Take Si/Cr nanomembrane as an example, we confirm that the three-dimensional structural formation is governed by both the minimum energy state and the geometric constraints imposed by the edges of the sacrificial layer. Large-scale, high-yield fabrication of three-dimensional structures is achieved, and two distinct three-dimensional structures are assembled from the same precursor. Six types of three-dimensional Si/Cr photodetectors are then prepared to resolve the incident angle of light with a deep neural network model, opening up possibilities for the design and manufacturing methods of More-than-Moore-era devices.

Enhanced photothermoelectric conversion in self-rolled tellurium photodetector with geometry-induced energy localization.

Photodetection has attracted significant attention for information transmission. While the implementation relies primarily on the photonic detectors, they are predominantly constrained by the intrinsic bandgap of active materials. On the other hand, photothermoelectric (PTE) detectors have garnered substantial research interest for their promising capabilities in broadband detection, owing to the self-driven photovoltages induced by the temperature differences. To get higher performances, it is crucial to localize light and heat energies for efficient conversion. However, there is limited research on the energy conversion in PTE detectors at micro/nano scale. In this study, we have achieved a two-order-of-magnitude enhancement in photovoltage responsivity in the self-rolled tubular tellurium (Te) photodetector with PTE effect. Under illumination, the tubular device demonstrates a maximum photovoltage responsivity of 252.13 V W-1 and a large detectivity of 1.48 × 1011 Jones. We disclose the mechanism of the PTE conversion in the tubular structure with the assistance of theoretical simulation. In addition, the device exhibits excellent performances in wide-angle and polarization-dependent detection. This work presents an approach to remarkably improve the performance of photodetector by concentrating light and corresponding heat generated, and the proposed self-rolled devices thus hold remarkable promises for next-generation on-chip photodetection.

One-step rolling fabrication of VO2 tubular bolometers with polarization-sensitive and omnidirectional detection.

Uncooled infrared detection based on vanadium dioxide (VO2) radiometer is highly demanded in temperature monitoring and security protection. The key to its breakthrough is to fabricate bolometer arrays with great absorbance and excellent thermal insulation using a straightforward procedure. Here, we show a tubular bolometer by one-step rolling VO2 nanomembranes with enhanced infrared detection. The tubular geometry enhances the thermal insulation, light absorption, and temperature sensitivity of freestanding VO2 nanomembranes. This tubular VO2 bolometer exhibits a detectivity of ~2 × 108 cm Hz1/2 W-1 in the ultrabroad infrared spectrum, a response time of ~2.0 ms, and a calculated noise-equivalent temperature difference of 64.5 mK. Furthermore, our device presents a workable structural paradigm for polarization-sensitive and omnidirectional light coupling bolometers. The demonstrated overall characteristics suggest that tubular bolometers have the potential to narrow performance and cost gap between photon detectors and thermal detectors with low cost and broad applications.

Self-Rolled-Up Ultrathin Single-Crystalline Silicon Nanomembranes for On-Chip Tubular Polarization Photodetectors.

Freestanding single-crystalline nanomembranes and their assembly have broad application potential in photodetectors for integrated chips. However, the release and self-assembly process of single-crystalline semiconductor nanomembranes still remains a great challenge in on-chip processing and functional integration, and photodetectors based on nanomembrane always suffer from limited absorption of nanoscale thickness. Here, a non-destructive releasing and rolling process is employed to prepare tubular photodetectors based on freestanding single-crystalline Si nanomembranes. Spontaneous release and self-assembly are achieved by residual strain introduced by lattice mismatch at the epitaxial interface of Si and Ge, and the intrinsic stress and strain distributions in self-rolled-up Si nanomembranes are analyzed experimentally and computationally. The advantages of light trapping and wide-angle optical coupling are realized by tubular geometry. This Si microtube device achieves reliable Ohmic contact and exhibits a photoresponsivity of over 330 mA W-1 , a response time of 370 µs, and a light incident detection angle range of over 120°. Furthermore, the microtubular structure shows a distinct polarization angle-dependent light absorption, with a dichroic ratio of 1.24 achieved at 940 nm. The proposed Si-based microtubes provide new possibilities for the construction of multifunctional chips for integrated circuit ecosystems in the More than Moore era.

Self-Rolling of Monolayer Graphene for Ultrasensitive Molecular Sensing.

The controllable manipulation of graphene to create three-dimensional (3D) structures is an intriguing approach for favorably tuning its properties and creating new types of 3D devices. However, due to extremely low bending stiffnesses, it is rather challenging to construct monolayer graphene into stable 3D structures. Here, we demonstrate the stable formation of monolayer graphene microtubes with accompanying pre-patterned strain layers. The diameter of graphene microtubes can be effectively tuned by changing the thickness of the strain layers. Benefiting from a high surface-to-volume ratio of the tubular geometry, the 3D geometry leads to a prominent Raman enhancement, which was further applied to molecular sensing. The R6G molecules on graphene microtubes can be detected even for a concentration as low as 10-11 M. We believe that this method can be a generalized way to realize the 3D tubular structure of other 2D materials.

Flying Squirrel-Inspired Motion Control of a Light-Deformed Pt-PAzoMA Micromotor through Drag Force Manipulation.

Micromotors require stable and precise motion control for complex tasks such as microsurgery, drug delivery in vivo, or environmental monitoring ex vivo. However, a continuous control signal is needed for micromotors to achieve motion control during their whole journey, which hinders their application in areas where external control stimuli are limited or unavailable. Fortunately, nature suggests an excellent solution that flying squirrel exhibits motion tuning capability by deforming itself when jumping off a tall tree. Inspired by this, we propose a Pt-PAzoMA Janus micromotor that precisely changes its shape (from a spherical shape to an elliptical shape) under a brief light signal (450 nm) and maintains this deformation until next signal reception. The deformed elliptical micromotor performs relatively low-speed motion compared to the spherical one, which is further confirmed by massive simulation results. In addition, by investigating motion behavior experimentally and theoretically, it is proved that the motion modulation is caused by the drag force changing brought from the deformation. This method represents a different route to regulate the motion of micromotors without a continuous signal, which is useful in application scenarios where the environmental control signal is inaccessible/limited or long-time operation with minimum energy input is required to maintain motion manipulation. With further function modification, this kind of shape-changing micromotor has potential in optimizing drug diffusion efficiency by speed altering and long-term monitoring at the diseased area by confining the active range of the micromotor in the targeted area through deformation.

Integration of a Metal-Organic Framework Film with a Tubular Whispering-Gallery-Mode Microcavity for Effective CO2 Sensing.

Carbon dioxide (CO2) sensing using an optical technique is of great importance in the environment and industrial emission monitoring. However, limited by the poor specific adsorption of gas molecules as well as insufficient coupling efficiency, there is still a long way to go toward realizing a highly sensitive optical CO2 gas sensor. Herein, by combining the advantages of a whispering-gallery-mode microcavity and a metal-organic framework (MOF) film, a porous functional microcavity (PF-MC) was fabricated with the assistance of the atomic layer deposition technique and was applied to CO2 sensing. In this functional composite, the rolled-up microcavity provides the ability to tune the propagation of light waves and the electromagnetic coupling with the surroundings via an evanescent field, while the nanoporous MOF film contributes to the specific adsorption of CO2. The composite demonstrates a high sensitivity of 188 nm RIU-1 (7.4 pm/% with respect to the CO2 concentration) and a low detection limit of ∼5.85 × 10-5 RIU. Furthermore, the PF-MC exhibits great selectivity to CO2 and outstanding reproducibility, which is promising for the next-generation optical gas sensing devices.

Resveratrol decreases high glucose­induced apoptosis in renal tubular cells via suppressing endoplasmic reticulum stress.

Diabetic nephropathy (DN) is the second most common complication of diabetes mellitus after cardiovascular complications. Endoplasmic reticulum (ER) stress is known to be associated with DN. Resveratrol (RSV) exhibits anti­oxidative, anti­inflammatory and cytoprotective effects. Therefore, the aims of the present study were to investigate the role of RSV in the inhibition of high concentration glucose (HG)­induced apoptosis in renal tubular cells, as well as to examine the protective effects of RSV against diabetes­mediated renal damage via inhibition of ER stress in DN. RSV was orally administered to diabetic db/db mice once a day for 12 consecutive weeks. Compared with untreated db/db mice, treating db/db mice with RSV significantly decreased urine albumin excretion and the urine albumin to creatinine ratio, and attenuated renal histopathological injury. Furthermore, RSV treatment resulted in decreased expression levels of glucose­regulated protein of 78 kDa and C/EBP­homologous protein (two ER stress markers) and caspase12 in murine kidneys. RSV administration also inhibited the apoptosis of NRK­52E cells and activation of the ER stress signal transduction pathway induced by HG treatment in vitro. Collectively, the present results indicated that RSV protected renal tubular cells against HG­induced apoptosis in DN by suppressing ER stress.

Silicon nanomembrane phototransistor flipped with multifunctional sensors toward smart digital dust.

The sensing module that converts physical or chemical stimuli into electrical signals is the core of future smart electronics in the post-Moore era. Challenges lie in the realization and integration of different detecting functions on a single chip. We propose a new design of on-chip construction for low-power consumption sensor, which is based on the optoelectronic detection mechanism with external stimuli and compatible with CMOS technology. A combination of flipped silicon nanomembrane phototransistors and stimuli-responsive materials presents low-power consumption (CMOS level) and demonstrates great functional expansibility of sensing targets, e.g., hydrogen concentration and relative humidity. With a device-first, wafer-compatible process introduced for large-scale silicon flexible electronics, our work shows great potential in the development of flexible and integrated smart sensing systems for the realization of Internet of Things applications.