Enzymatic colorimetric analysis of metabolites provides signatures of energy conversion and biosynthesis associated with disease onsets and progressions. Miniaturized photodetectors based on emerging two-dimensional transition metal dichalcogenides (TMDCs) promise to advance point-of-care diagnosis employing highly sensitive enzymatic colorimetric detection. Reducing diagnosis costs requires a batched multisample assay. The construction of few-layer TMDC photodetector arrays with consistent performance is imperative to realize optical signal detection for a miniature batched multisample enzymatic colorimetric assay. However, few studies have promoted an optical reader with TMDC photodetector arrays for on-chip operation. Here, we constructed 4 × 4 pixel arrays of miniaturized molybdenum disulfide (MoS2) photodetectors and integrated them with microfluidic enzyme reaction chambers to create an optoelectronic biosensor chip device. The fabricated device allowed us to achieve arrayed on-chip enzymatic colorimetric detection of d-lactate, a blood biomarker signifying the bacterial translocation from the intestine, with a limit of detection that is 1000-fold smaller than the clinical baseline, a 10 min assay time, high selectivity, and reasonably small variability across the entire arrays. The enzyme (Ez)/MoS2 optoelectronic biosensor unit consistently detected d-lactate in clinically important biofluids, such as saliva, urine, plasma, and serum of swine and humans with a wide detection range (10–3–103 μg/mL). Furthermore, the biosensor enabled us to show that high serum d-lactate levels are associated with the symptoms of systemic infection and inflammation. The lensless, optical waveguide-free device architecture should readily facilitate development of a monolithically integrated hand-held module for timely, cost-effective diagnosis of metabolic disorders in near-patient settings.
Two-dimensional layered transition-metal dichalcogenides have drawn enormous interest because of their desired electrical and mechanical properties for making various devices with attractive functions. However, the device fabrication process typically introduces lithography-induced contamination and damage to such fragile and sensitive atomically layered materials. Here, we present a multiplexing lithography process system capable of directly generating few-layer molybdenum disulfide (MoS2) feature arrays with no need of additional lithographic or etching steps. This process combines a site-selective growth scheme based on mechanically generated triboelectric charge patterns and programmable actuation of rubbing templates bearing 2D feature arrays. To achieve a good processing uniformity, we have systematically investigated the effects of implementation of an air cushion on the rubbing template, various interfacing layers on the rubbing features, as well as mechanical load on rubbing templates and substrates. Using this process, we have demonstrated the growth of “L” shaped few-layer MoS2 arrays on SiO2/Si substrates with a good yield.
We investigate the oscillatory dynamics of an epidemiological model of SIRS(susceptible-infectiverecovered-susceptible) type on small-world networks. A delay differential equation for the infected population is derived to show that three characteristic patterns, stationarity, oscillation, and synchronized extermination exist, depending on the competition between the disease's life cycle and the time for it to sweep the world. Numerical calculations support this prediction and suggest that the synchronization parameter proposed by Kuramoto can be a good measure of patterns.
The ability to detect low‐abundance proteins in human body fluids plays a critical role in proteomic research to achieve a comprehensive understanding of protein functions and early‐stage disease diagnosis to reduce mortality rates. Ultrasensitive (sub‐fM), rapid, simple “mix‐and‐read” plasmonic colorimetric biosensing of large‐size (≈180 kDa) proteins in biofluids using an ultralow‐noise multilayer molybdenum disulfide (MoS2) photoconducting channel is reported here. With its out‐of‐plane structure optimized to minimize carrier scattering, the multilayer MoS2 channel operated under near‐infrared illumination enables the detection of a subtle plasmonic extinction shift caused by antigen‐induced nanoprobe aggregation. The demonstrated biosensing strategy allows quantifying carcinoembryonic antigen in unprocessed whole blood with a dynamic range of 106, a sample‐to‐answer time of 10 min, and a limit of detection of 0.1–3 pg mL−1, which is ≈100‐fold more sensitive than the clinical‐standard enzyme‐linked immunosorbent assays. The biosensing methodology can be broadly used to realize timely personalized diagnostics and physiological monitoring of diseases in point‐of‐care settings.
Directly identifying the presence of the virus in infected hosts with an appropriate speed and sensitivity permits early epidemic management even during the presymptomatic incubation period of infection. Here, we synthesize a bioinspired plasmo-virus (BPV) particle for rapid and sensitive point-of-care (POC) detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) via a selfassembled plasmonic nanoprobe array on spike proteins. The BPV enables strong near-infrared (NIR) extinction peaks caused by plasmonic nanogaps. We quantify SARS-CoV-2 in viral transport medium (VTM) at low titers within 10 min with a limit of detection (LOD) of 1.4 × 10 1 pfu/mL, which is 10 3 times more sensitive than the current gold-standard method. The high-sensitivity and high-speed POC detection may be widely used for the timely, individualized diagnosis of infectious agents in low-resource settings.
Plasmonic Colorimetric Biosensing of Proteins in Biofluids In article number 2101291, Younggeun Park, Xiaogan Liang, Katsuo Kurabayashi, and co‐workers demonstrate rapid, “mix‐and‐read” detection of cancer marker proteins at sub‐femtomolar concentrations in unprocessed whole blood using a multilayered molybdenum disulfide photoconductive channel and plasmonic nanoparticles. Minimized carrier scattering within the photoconductive channel allows for detecting subtle near‐infrared light transmission shifts accompanying antigen‐induced plasmonic nanoparticle aggregation in blood.
Bismuth selenide (Bi 2 Se 3 ), a layered semiconductor, has attracted a great deal of attention as a thermoelectric material as well as a potential topological insulator. Here, we present a work showing that Bi 2 Se 3 can also be used for making memristive devices capable of directly processing analog video signals. In this work, Bi 2 Se 3 memristors are produced by multiplexing rubbing-induced site-selective growth, which potentially enables scalable implementation of such memristor arrays for constructing large-scale neuromorphic systems. The fabricated Bi 2 Se 3 memristors exhibit prominent memristive switching characteristics under the application of time-sequential voltage pulses. Especially, such a Bi 2 Se 3 memristor exhibits a reliable dependence of memristive responses on the duty cycle of programming pulses, fast recovery behavior from a dynamically modulated state, and a large drive current. These properties could be employed for extracting spatiotemporal information from analogue signals and realizing practical neuromorphic sensory functions. Our additional tests strongly imply that the memristive output of a Bi 2 Se 3 memristor in response to analogue video scanline signals could be implemented to construct future hardware-based computer vision systems capable of rapidly acquiring graphic information and directly actuating robotic systems with minimal data transmission and energy consumption. Finally, we attribute the observed memristive characteristics to field-mediated drift and diffusion of the selenium vacancies in the Bi 2 Se 3 layers. The simulated memristive response based on this hypothesis model is consistent with the experimental result. This work provides a potentially upscalable device solution to realize memristor-based neuromorphic sensory or edge computing systems.
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