[Show abstract][Hide abstract] ABSTRACT: Label-free MoS2 nanosheet-based field-effect biosensor detects cancer marker protein Prostate Specific Antigen in real time with high sensitivity and selectivity, exhibiting great potential in point-of-care diagnostics application.
[Show abstract][Hide abstract] ABSTRACT: We engineered functional cardiac patches by seeding neonatal rat cardiomyocytes onto carbon nanotube (CNT) incorporated photocrosslinkable gelatin methacrylate (GelMA) hydrogel. The resulting cardiac constructs showed excellent mechanical integrity and advanced electrophysiological functions. Specifically, myocardial tissues cultured on 50 μm thick CNT-GelMA showed 3 times higher spontaneous synchronous beating rates and 85% lower excitation threshold, compared to those cultured on pristine GelMA hydrogels. Our results indicate that the electrically conductive and nanofibrous networks formed by CNTs within a porous gelatin framework is the key characteristics of CNT-GelMA leading to improved cardiac cell adhesion, organization, and cell-cell coupling. Centimeter-scale patches were released from glass substrates to form 3D biohybrid actuators, which showed controllable linear cyclic contraction/extension, pumping, and swimming actuations. In addition, we demonstrate for the first time that cardiac tissues cultured on CNT-GelMA resist damage by a model cardiac inhibitor as well as a cytotoxic compound. Therefore, incorporation of CNTs into gelatin, and potentially other biomaterials, could be useful in creating multifunctional cardiac scaffolds for both therapeutic purposes and in vitro studies. These hybrid materials could also be used for neuron and other muscle cells to create tissue constructs with improved organization, electroactivity, and mechanical integrity.
[Show abstract][Hide abstract] ABSTRACT: Aerogels have numerous applications due to their high surface area and low densities. However, creating aerogels from a large variety of materials has remained an outstanding challenge. Here, we report a new methodology to enable aerogel production with a wide range of materials. The method is based on the assembly of anisotropic nano-objects (one-dimensional (1D) nanotubes, nanowires, or two-dimensional (2D) nanosheets) into a cross-linking network from their colloidal suspensions at the transition from the semi-dilute to the isotropic concentrated regime. The resultant aerogels have highly porous and ultrafine three-dimensional (3D) networks consisting of 1D (Ag, Si, MnO(2), single-walled carbon nanotubes (SWNTs)) and 2D materials (MoS(2), graphene, h-BN) with high surface areas, low densities, and high electrical conductivities. This method opens up a facile route for aerogel production with a wide variety of materials and tremendous opportunities for bio-scaffold, energy storage, thermoelectric, catalysis, and hydrogen storage applications.
[Show abstract][Hide abstract] ABSTRACT: Graphene wires have been fabricated from large-area multilayer graphene sheets grown by chemical vapor deposition. As the methane concentration increases, a larger percentage of thicker graphene layers are grown. The multilayer graphene sheets have an average thickness of 10-20 nm with sheet resistances between 500 and 1000 Ω/sq. The sheet resistance shows a strong correlation with the average surface roughness. This letter reports measured breakdown current densities up to 4×10<sup>7</sup> A/cm<sup>2</sup>, where resistive heating is proposed as the main breakdown mechanism. Increasing the uniformity of the graphene layers is important in achieving a higher breakdown current density.
IEEE Electron Device Letters 05/2011; · 3.02 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Carbon-based nanomaterials such as metallic single-walled carbon nanotubes, multiwalled carbon nanotubes (MWCNTs), and graphene have been considered as some of the most promising candidates for future interconnect technology because of their high current-carrying capacity and conductivity in the nanoscale, and immunity to electromigration, which has been a great challenge for scaling down the traditional copper interconnects. Therefore, studies on the performance and optimization of carbon-based interconnects working in a realistic operational environment are needed in order to advance the technology beyond the exploratory discovery phase. In this paper, we present the first demonstration of graphene interconnects monolithically integrated with industry-standard complementary metal-oxide-semiconductor technology, as well as the first experimental results that compare the performance of high-speed on-chip graphene and MWCNT interconnects. The graphene interconnects operate up to 1.3-GHz frequency, which is a speed that is commensurate with the fastest high-speed processor chips today. A low-swing signaling technique has been applied to improve the speed of carbon interconnects up to 30%.
IEEE Transactions on Electron Devices 12/2010; · 2.36 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In this paper, we characterize the performance of monolithically integrated graphene interconnects on a prototype 0.35-μm CMOS chip. The test chip implements an array of transmitter/receivers to analyze the end-to-end data communication on graphene wires. Large-area graphene sheets are first grown by chemical vapor deposition, which are then subsequently processed into narrow wires up to 1 mm in length. A low-swing signaling technique is applied, which results in a transmitter energy of 0.3-0.7 pJ/b·mm-1 and a total energy of 2.4-5.2 pJ/b·mm-1. Bit error rates below 2 × 10-10 are measured using a 231 - 1 pseudorandom binary sequence. Minimum voltage swings of 100 mV at 1.5-V supply and 500 mV at 3.3-V supply have also been demonstrated. At present, the graphene wire is largely limited by its growth quality and high sheet resistance.
IEEE Transactions on Electron Devices 12/2010; 57(12):3418-3425. · 2.36 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Graphene has been considered as one of the most promising candidates for future interconnect technology. In spite of the promising theoretical predictions and DC characterization results about the excellent current-carrying capability of graphene nanoribbons, experimental demonstration and characterization of high speed signaling performance of graphene interconnects is still very limited. Here we present the first monolithic integration of graphene with commercial CMOS technology and the first experimental demonstration of on-chip graphene interconnects that operates above 1 GHz. We also studied the the dependence of high frequency performance on graphene interconnect physical dimensions. Important physical parameters like mean free path of graphene are extracted from experimental data. We compared our experimental results with previous theoretical predictions and gave experimental performance projection of on-chip graphene nanoribbon interconnects with linewidth smaller than 100nm.
[Show abstract][Hide abstract] ABSTRACT: We have successfully experimentally integrated graphene interconnects with commercial 0.25 Â¿m technology CMOS ring oscillator circuit using conventional fabrication techniques, and demonstrated high speed on-chip graphene interconnects that operates above 1 GHz.
Electron Devices Meeting (IEDM), 2009 IEEE International; 01/2010
[Show abstract][Hide abstract] ABSTRACT: This chapter provides an overview of recent research on inorganic nanowires, particularly metallic and semiconducting nanowires.
one-dimensional, anisotropic structures, small in diameter, and large in surface-to-volume ratio. Thus, their physical properties
are different than those of structures of different scale and dimensionality. While the study of nanowires is particularly
challenging, scientists have made immense progress in both developing synthetic methodologies for the fabrication of nanowires,
and developing instrumentation for their characterization. The chapter is divided into three main sections: Sect.4.1 the synthesis, Sect.4.2 the characterization and physical properties, and Sect.4.3 the applications of nanowires. Yet, the reader will discover many links that make these aspects of nanoscience intimately
[Show abstract][Hide abstract] ABSTRACT: This paper presents an energy-efficient chemical sensor system that uses carbon nanotubes (CNT) as the sensing medium. The room-temperature operation of CNT sensors eliminates the need for micro hot-plate arrays, which enables the low energy operation of the system. An array of redundant CNT sensors overcomes the reliability issues incurred by the CNT process variation. The sensor interface chip is designed to accommodate a 16-bit dynamic range by adaptively controlling an 8-bit DAC and a 10-bit ADC. A discrete optimization methodology determines the dynamic range of the DAC and the ADC to minimize the energy consumption of the system. A simple calibration technique using off-chip reference resistors reduces the DAC non-linearity. The sensor interface chip is designed in a 0.18-mum CMOS process and consumes, at maximum, 32 muW at 1.83 kS/s conversion rate. The designed interface achieves 1.34% measurement accuracy across the 10 kOmega-9 MOmega range. The functionality of the full system, including CNT sensors, has been successfully demonstrated.
IEEE Journal of Solid-State Circuits 03/2009; · 3.11 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: This paper presents a hybrid CNT/CMOS chemical sensor system that comprises of a carbon nanotube sensor array and a CMOS interface chip. The full system, including the sensor, consumes 32 muW at 1.83 kS/s readout rate, accomplished through an extensive use of CAD tools and a model-based architecture optimization. A redundant use of CNT sensors in the frontend increases the reliability of the system.
[Show abstract][Hide abstract] ABSTRACT: The construction of nanoporous membranes is of great technological importance for various applications, including catalyst supports, filters for biomolecule purification, environmental remediation and seawater desalination. A major challenge is the scalable fabrication of membranes with the desirable combination of good thermal stability, high selectivity and excellent recyclability. Here we present a self-assembly method for constructing thermally stable, free-standing nanowire membranes that exhibit controlled wetting behaviour ranging from superhydrophilic to superhydrophobic. These membranes can selectively absorb oils up to 20 times the material's weight in preference to water, through a combination of superhydrophobicity and capillary action. Moreover, the nanowires that form the membrane structure can be re-suspended in solutions and subsequently re-form the original paper-like morphology over many cycles. Our results suggest an innovative material that should find practical applications in the removal of organics, particularly in the field of oil spill cleanup.
[Show abstract][Hide abstract] ABSTRACT: This paper presents an energy efficient chemical sensor system that uses carbon nanotubes (CNT) as the sensor. The room-temperature operation of CNT sensors eliminates the need for micro hot-plate arrays, which enables the low energy operation of the system. The sensor interface chip is designed in a 0.18 mum CMOS process and consumes, at maximum, 32 muW at 1.83 kS/s conversion rate. The designed interface achieves 1.34% measurement accuracy over 10 kOmega -9 MOmega dynamic range. The functionality of the full system, including CNT sensors, has been successfully demonstrated.
[Show abstract][Hide abstract] ABSTRACT: Carbon nanotubes (CNTs) are nanometer-diameter cylinders formed from rolled-up graphene sheets . CNTs have found ne sheets . CNTs have found e sheets . CNTs have found . CNTs have found . CNTs have found widespread interest due to many of its excellent electrical prop-electrical prop-prop-erties. In particular, the low density and high electron mobility of CNTs make them attractive for electronic applications. Our investigation of hybrid CMOS-CNT systems attempts to take ad-vantage of the superior properties of CNTs while building on top of existing CMOS technology. technology. . We propose an integrated chemical sensor system to verify the concept of a CNT-CMOS hybrid system design. The CNT . The CNT The CNT changes its conductance when exposed to certain chemicals, and thus we can effectively use CNTs as resistive chemical sensors . use CNTs as resistive chemical sensors . CNTs as resistive chemical sensors . . . Room-temperature operation of the CNT sensors makes them an oom-temperature operation of the CNT sensors makes them an sensors makes them an an appealing candidate for low-power chemical sensor application. However, poor control over the local and global variation of CNT over the local and global variation of CNT the local and global variation of CNT local and global variation of CNT and global variation of CNT global variation of CNT CNT devices, the resolution requirements in resistance measurements, s, the resolution requirements in resistance measurements, , the resolution requirements in resistance measurements, and the changes in resistance due to specific chemicals implies a large dynamic range in the front-end circuitry. We investigate in the front-end circuitry. We investigate in the front-end circuitry. We investigate energy efficient architectures to accommodate the specification (Figure 1). Chip fabrication is done by National Semiconductor.