Coronavirus disease 2019 (COVID-19) is a newly emerging human infectious disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2, previously called 2019-nCoV). Based on the rapid increase in the rate of human infection, the World Health Organization (WHO) has classified the COVID-19 outbreak as a pandemic. Because no specific drugs or vaccines for COVID-19 are yet available, early diagnosis and management are crucial for containing the outbreak. Here, we report a field-effect transistor (FET)-based biosensing device for detecting SARS-CoV-2 in clinical samples. The sensor was produced by coating graphene sheets of the FET with a specific antibody against SARS-CoV-2 spike protein. The performance of the sensor was determined using antigen protein, cultured virus, and nasopharyngeal swab specimens from COVID-19 patients. Our FET device could detect the SARS-CoV-2 spike protein at concentrations of 1 fg/mL in phosphate-buffered saline and 100 fg/mL clinical transport medium. In addition, the FET sensor successfully detected SARS-CoV-2 in culture medium (limit of detection [LOD]: 1.6 × 101 pfu/mL) and clinical samples (LOD: 2.42 × 102 copies/mL). Thus, we have successfully fabricated a promising FET biosensor for SARS-CoV-2; our device is a highly sensitive immunological diagnostic method for COVID-19 that requires no sample pretreatment or labeling.

Rapid Detection of COVID-19 Causative Virus (SARS-CoV-2) in Human Nasopharyngeal Swab Specimens Using Field-Effect Transistor-Based Biosensor.

A strain sensor has been fabricated from a polymer nanocomposite with multiwalled carbon nanotube (MWNT) fillers. The piezoresistivity
of this nanocomposite strain sensor has been investigated based on an improved three-dimensional (3D) statistical resistor network
model incorporating the tunneling effect between the neighboring carbon nanotubes (CNTs), and a fiber reorientation model. The
numerical results agree very well with the experimental measurements. As compared with traditional strain gauges, much higher sensitivity
can be obtained in the nanocomposite sensors when the volume fraction of CNT is close to the percolation threshold. For a small
CNT volume fraction, weak nonlinear piezoresistivity is observed both experimentally and from numerical simulation. The tunneling
effect is considered to be the principal mechanism of the sensor under small strains.

Tunneling effect in a polymer/carbon nanotube nanocompositestrain sensor

Recent advances in soft materials and system integration technologies have provided a unique opportunity to design various types of wearable flexible hybrid electronics (WFHE) for advanced human healthcare and human-machine interfaces. The hybrid integration of soft and biocompatible materials with miniaturized wireless wearable systems is undoubtedly an attractive prospect in the sense that the successful device performance requires high degrees of mechanical flexibility, sensing capability, and user-friendly simplicity. Here, the most up-to-date materials, sensors, and system-packaging technologies to develop advanced WFHE are provided. Details of mechanical, electrical, physicochemical, and biocompatible properties are discussed with integrated sensor applications in healthcare, energy, and environment. In addition, limitations of the current materials are discussed, as well as key challenges and the future direction of WFHE. Collectively, an all-inclusive review of the newly developed WFHE along with a summary of imperative requirements of material properties, sensor capabilities, electronics performance, and skin integrations is provided.

Advanced Soft Materials, Sensor Integrations, and Applications of Wearable Flexible Hybrid Electronics in Healthcare, Energy, and Environment.

High-performance top-gated carbon nanotube field-effect transistors (CNT FETs) with a gate length of 5 nanometers can be fabricated that perform better than silicon complementary metal-oxide semiconductor (CMOS) FETs at the same scale. A scaling trend study revealed that the scaled CNT-based devices, which use graphene contacts, can operate much faster and at much lower supply voltage (0.4 versus 0.7 volts) and with much smaller subthreshold slope (typically 73 millivolts per decade). The 5-nanometer CNT FETs approached the quantum limit of FETs by using only one electron per switching operation. In addition, the contact length of the CNT CMOS devices was also scaled down to 25 nanometers, and a CMOS inverter with a total pitch size of 240 nanometers was also demonstrated.

http://science.sciencemag.org/content/sci/355/6322/271.full.pdf

Scaling carbon nanotube complementary transistors to 5-nm gate lengths

Electronics is approaching a major paradigm shift because silicon transistor scaling no longer yields historical energy-efficiency benefits, spurring research towards beyond-silicon nanotechnologies. In particular, carbon nanotube field-effect transistor (CNFET)-based digital circuits promise substantial energy-efficiency benefits, but the inability to perfectly control intrinsic nanoscale defects and variability in carbon nanotubes has precluded the realization of very-large-scale integrated systems. Here we overcome these challenges to demonstrate a beyond-silicon microprocessor built entirely from CNFETs. This 16-bit microprocessor is based on the RISC-V instruction set, runs standard 32-bit instructions on 16-bit data and addresses, comprises more than 14,000 complementary metal–oxide–semiconductor CNFETs and is designed and fabricated using industry-standard design flows and processes. We propose a manufacturing methodology for carbon nanotubes, a set of combined processing and design techniques for overcoming nanoscale imperfections at macroscopic scales across full wafer substrates. This work experimentally validates a promising path towards practical beyond-silicon electronic systems. A 16-bit microprocessor built from over 14,000 carbon nanotube transistors may enable energy efficiency advances in electronics technologies beyond silicon.

Modern microprocessor built from complementary carbon nanotube transistors

Field-effect transistor (FET) biosensors based on low-dimensional materials present the advantages of low cost, high speed, small size, and excellent compatibility with integrated circuits (ICs). In this work, we fabricated highly sensitive FET-based DNA biosensors based on chemical vapor deposition (CVD)-grown monolayer MoS2 films in batches and explored their application in noninvasive prenatal testing (NIPT) for trisomy 21 syndrome. Specifically, MoS2 was functionalized with gold nanoparticles (Au NPs) of an optimized size and at an ideal density, and then, probe DNAs for the specific capture of target DNAs were immobilized on the nanoparticles. The fabricated FET biosensors are able to reliably detect target DNA fragments (chromosome 21 or 13) with a detection limit below 100 aM, a high response up to 240%, and a high specificity, which satisfy the requirement for the screening of Down syndrome. In addition, a real-time test was conducted to show that the biosensor clearly responds to the target DNA a...

Ultrasensitive Monolayer MoS2 Field-Effect Transistor Based DNA Sensors for Screening of Down Syndrome.

Progress in the controlled synthesis and post-growth treatment of carbon nanotubes has led to the fabrication of nanotube-based field-effect transistors with intrinsic performance close to the ballistic limits. However, nanotube-based integrated circuits (ICs) developed to date typically have a working frequency of less than 1 MHz, which is well below the working frequency of silicon ICs. Here we show that the speed of carbon nanotube ICs can be significantly improved by optimizing device structure and fabrication processes, yielding ICs that work in the gigahertz regime. Based on high-performance nanotube film field-effect transistors, five-stage ring oscillators were batch fabricated and shown to exhibit an oscillation frequency of up to 5.54 GHz. This is twenty times higher than that of the leading nanotube IC (a five-stage ring oscillator with an oscillation frequency of 282 MHz). Using field-effect transistors made from carbon nanotube films, five-stage ring oscillators can be fabricated that exhibit an oscillation frequency of up to 5.54 GHz.

Gigahertz integrated circuits based on carbon nanotube films

Intrinsically stretchable bioelectronic devices based on soft and conducting organic materials have been regarded as the ideal interface for seamless and biocompatible integration with the human body. A remaining challenge is to combine high mechanical robustness with good electrical conduction, especially when patterned at small feature sizes. We develop a molecular engineering strategy based on a topological supramolecular network, which allows for the decoupling of competing effects from multiple molecular building blocks to meet complex requirements. We obtained simultaneously high conductivity and crack-onset strain in a physiological environment, with direct photopatternability down to the cellular scale. We further collected stable electromyography signals on soft and malleable octopus and performed localized neuromodulation down to single-nucleus precision for controlling organ-specific activities through the delicate brainstem. Description Designing the right polymer blend Approaches to making soft electronics can involve putting rigid objects onto a soft substrate or finding ways to improve the conductivity and mechanical strength of inherently soft materials. Jiang et al. considered the systematic introduction of polyrotaxanes into soft conductive membranes made of the conductive polymer poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS). The polyrotaxane consisted of a polyethylene glycol (PEG) backbone with cyclodextrins attached using PEG-methacrylate side chains. The cyclodextrins can slide back and forth along the chains, thus preventing crystallization of the PEG and providing better stretchability. The blended polymers could be photopatterned down to two-micrometer feature sizes and exhibited enhanced conductivity, making them suitable for surface-mounted and implanted bioelectronic devices. —MSL A stretchable conducting polymer allows stable monitoring of soft-bodied octopus and precise modulation of delicate brainstem.

Topological supramolecular network enabled high-conductivity, stretchable organic bioelectronics

Polymeric electronic materials have enabled soft and stretchable electronics. However, the lack of a universal micro/nanofabrication method for skin-like and elastic circuits results in low device density and limited parallel signal recording and processing ability relative to silicon-based devices. We present a monolithic optical microlithographic process that directly micropatterns a set of elastic electronic materials by sequential ultraviolet light-triggered solubility modulation. We fabricated transistors with channel lengths of 2 micrometers at a density of 42,000 transistors per square centimeter. We fabricated elastic circuits including an XOR gate and a half adder, both of which are essential components for an arithmetic logic unit. Our process offers a route to realize wafer-level fabrication of complex, high-density, and multilayered elastic circuits with performance rivaling that of their rigid counterparts.

Donglai Zhong

Papers

Scaling carbon nanotube complementary transistors to 5-nm gate lengths

Ultrasensitive Monolayer MoS2 Field-Effect Transistor Based DNA Sensors for Screening of Down Syndrome.

Gigahertz integrated circuits based on carbon nanotube films

Topological supramolecular network enabled high-conductivity, stretchable organic bioelectronics

Monolithic optical microlithography of high-density elastic circuits.