Seamless and minimally-invasive three-dimensional (3D) interpenetration of electronics within artificial or natural structures could allow for continuous monitoring and manipulation of their properties. Flexible electronics provide a means for conforming electronics to non-planar surfaces, yet targeted delivery of flexible electronics to internal regions remains difficult. Here, we overcome this challenge by demonstrating syringe injection and subsequent unfolding of submicrometer-thick, centimeter-scale macroporous mesh electronics through needles with a diameter as small as 100 micrometers. Our results show that electronic components can be injected into man-made and biological cavities, as well as dense gels and tissue, with > 90% device yield. We demonstrate several applications of syringe injectable electronics as a general approach for interpenetrating flexible electronics with 3D structures, including (i) monitoring of internal mechanical strains in polymer cavities, (ii) tight integration and low chronic immunoreactivity with several distinct regions of the brain, and (iii) in vivo multiplexed neural recording. Moreover, syringe injection enables delivery of flexible electronics through a rigid shell, delivery of large volume flexible electronics that can fill internal cavities and co-injection of electronics with other materials into host structures, opening up unique applications for flexible electronics.

By combining atomic force microscopy and trans-port measurements, we systematically investigated effects of thermal annealing on surface morphologies and electrical properties of single-layer graphene devices fabricated by electron beam lithography on silicon oxide (SiO(2)) substrates. Thermal treatment above 300 °C in vacuum was required to effectively remove resist residues on graphene surfaces. However, annealing at high temperature was found to concomitantly bring graphene in close contact with SiO(2) substrates and induce increased coupling between them, which leads to heavy hole doping and severe degradation of mobilities in graphene devices. To address this problem, a wet-chemical approach employing chloroform was developed in our study, which was shown to enable both intrinsic surfaces and enhanced electrical properties of graphene devices. Upon the recovery of intrinsic surfaces of graphene, the adsorption and assisted fibrillation of amyloid β-peptide (Aβ1-42) on graphene were electrically measured in real time.

Nanowire field-effect transistors (NW-FETs) have been shown to be powerful building blocks for nanoscale bioelectronic interfaces with cells and tissue due to their excellent sensitivity and their capability to form strongly coupled interfaces with cell membranes. Graphene has also been shown to be an attractive building block for nanoscale electronic devices, although little is known about its interfaces with cells and tissue. Here we report the first studies of graphene field effect transistors (Gra-FETs) as well as combined Gra-and NW-FETs interfaced to electrogenic cells. Gra-FET conductance signals recorded from spontaneously beating embryonic chicken cardiomyocytes yield well-defined extracellular signals with signal-to-noise ratio routinely >4. The conductance signal amplitude was tuned by varying the Gra-FET working region through changes in water gate potential, V wg . Signals recorded from cardiomyocytes for different V wg result in constant calibrated extracellular voltage, indicating a robust graphene/cell interface. Significantly, variations in V wg across the Dirac point demonstrate the expected signal polarity flip, thus allowing, for the first time, both n-and p-type recording to be achieved from the same Gra-FET simply by offsetting V wg . In addition, comparisons of peak-to-peak recorded signal widths made as a function of Gra-FET device sizes and versus NW-FETs allowed an assessment of relative resolution in extracellular recording. Specifically, peak-to-peak widths increased with the area of Gra-FET devices, indicating an averaged signal from different points across the outer membrane of the beating cells. One-dimensional silicon NW-FETs incorporated side by side with the two-dimensional Gra-FET devices further highlighted limits in both temporal resolution and multiplexed measurements from the same cell for the different types of devices. The distinct and complementary capabilities of Gra-and NW-FETs could open up unique opportunities in the field of bioelectronics in the future.Bioelectronic interfaces created with nanomaterials represents an exciting and growing field of research that exploits key nanomaterial properties to go well beyond the capabilities of conventional microfabricated electronics. 1-8 For example, several groups have recently reported electrical measurements from cells and tissue interfaced to NW-FETs, with results demonstrating high signal-to-noise recording from cultured neurons, muscle cells, embryonic chicken hearts and acute brain slices. [4][5][6][7][8] Unique features of these studies compared to conventional planar devices measurements, include (i) the exceptional small active area of the NW-FET devices and (ii) the fact that nanodevices protrude from the plane of the substrate. The former feature enables high spatial resolution, while the latter can increase device/cell interfacial coupling. Indeed, studies have shown that nanostructured interfaces can enhance cellular adhesion and activity, 9-14 and thus it is likely that NWs and other nanomaterials may...

Nanopores could potentially be used to perform single molecule DNA sequencing at low cost and with high throughput1–4. Although single-base resolution and differentiation have been demonstrated with nanopores using ionic current measurements5–7, direct sequencing has not been achieved due to difficulties in recording very small (~pA) ionic current at a bandwidth consistent with fast translocation speeds1–3. Here we show that solid-state nanopores can be combined with silicon nanowire field-effect transistors (FETs) to create sensors in which detection is localised and self-aligned at the nanopore. Well-defined FET signals associated with DNA translocation are recorded when an ionic strength gradient is imposed across the nanopores. Measurements and modelling show that FET signals are generated by highly-localized changes in the electrical potential during DNA translocation and that the nanowire-nanopore sensors could enable large-scale integration with a high intrinsic bandwidth.

1322 wileyonlinelibrary.com applications in fi elds of healthcare monitoring, human-computer interaction, and electronic skin. [ 12 ] The relative resistance Δ R normalized by the initial resistance R 0 depends on Poisson's ratio ( ν ) and resistivity variation (Δ ρ ) normalized by its initial resistivity ρ 0 through the expression ΔR / R 0 = (1 + 2ν) ε + Δ ρ / ρ 0.[ 13 ] The sensitivity revealed by gauge factor (GF, defi ned as ( ΔR / R 0 )/ ε ) depends on both intrinsic property and structural feature. According to this formula, graphene-based strain sensors have shown low sensitivities due to the rigid and stable structure of intrinsic graphene. [ 14 ] With hardly opened band gap, the GF of a suspended graphene is only about 1.9 under moderate uniaxial strains. [ 15 ] Therefore, structural engineering of graphene is needed to boost the sensitivity of graphene-based strain sensors.Adjustment of the connection channels in graphene is an effective way to alter its resistivity for improved sensitivity in strain sensors. Two common methods for the structural construction of graphene include high temperature processing based chemical vapor deposition (CVD) and solution processing based sheets/fl akes assembly. As for CVD, the resistivity of graphene would be affected by its grain boundary, grain size, and the defect density. [16][17][18] Continuous graphene fi lms grown by CVD could sustain 1% strain with a GF of only 6.1, [ 19 ] and the GF increases to 151 for a 5% strain due to the morphological Large-Area Ultrathin Graphene Films by Single-Step Marangoni Self-Assembly for Highly Sensitive Strain Sensing ApplicationXinming Li , Tingting Yang , Yao Yang , Jia Zhu , Li Li , Fakhr E. Alam , Xiao Li , Kunlin Wang , Huanyu Cheng , Cheng-Te Lin , * Ying Fang , * and Hongwei Zhu * Promoted by the demand for wearable devices, graphene has been proved to be a promising material for potential applications in fl exible and highly sensitive strain sensors. However, low sensitivity and complex processing of graphene retard the development toward the practical applications. Here, an environment-friendly and cost-effective method to fabricate large-area ultrathin graphene fi lms is proposed for highly sensitive fl exible strain sensor. The assembled graphene fi lms are derived rapidly at the liquid/air interface by Marangoni effect and the area can be scaled up. These graphene-based strain sensors exhibit extremely high sensitivity with gauge factor of 1037 at 2% strain, which represents the highest value for graphene platelets at this small deformation so far. This simple fabrication for strain sensors with highly sensitive performance of strain sensor makes it a novel approach to applications in electronic skin, wearable sensors, and health monitoring platforms.

A graphene/n-type silicon (n-Si) heterojunction has been demonstrated to exhibit strong rectifying behavior and high photoresponsivity, which can be utilized for the development of high-performance photodetectors. However, graphene/n-Si heterojunction photodetectors reported previously suffer from relatively low specific detectivity due to large dark current. Here, by introducing a thin interfacial oxide layer, the dark current of graphene/n-Si heterojunction has been reduced by two orders of magnitude at zero bias. At room temperature, the graphene/n-Si photodetector with interfacial oxide exhibits a specific detectivity up to 5.77 × 10(13) cm Hz(1/2) W(-1) at the peak wavelength of 890 nm in vacuum, which is highest reported detectivity at room temperature for planar graphene/Si heterojunction photodetectors. In addition, the improved graphene/n-Si heterojunction photodetectors possess high responsivity of 0.73 A W(-1) and high photo-to-dark current ratio of ≈10(7) . The current noise spectral density of the graphene/n-Si photodetector has been characterized under ambient and vacuum conditions, which shows that the dark current can be further suppressed in vacuum. These results demonstrate that graphene/Si heterojunction with interfacial oxide is promising for the development of high detectivity photodetectors.

Carbon nanotube-Si and graphene-Si solar cells have attracted much interest recently owing to their potential in simplifying manufacturing process and lowering cost compared to Si cells. Until now, the power conversion efficiency of graphene-Si cells remains under 10% and well below that of the nanotube-Si counterpart. Here, we involved a colloidal antireflection coating onto a monolayer graphene-Si solar cell and enhanced the cell efficiency to 14.5% under standard illumination (air mass 1.5, 100 mW/cm(2)) with a stable antireflection effect over long time. The antireflection treatment was realized by a simple spin-coating process, which significantly increased the short-circuit current density and the incident photon-to-electron conversion efficiency to about 90% across the visible range. Our results demonstrate a great promise in developing high-efficiency graphene-Si solar cells in parallel to the more extensively studied carbon nanotube-Si structures.

Flexible piezoresistive pressure sensors have been attracting wide attention for applications in health monitoring and human-machine interfaces because of their simple device structure and easy-readout signals. For practical applications, flexible pressure sensors with both high sensitivity and wide linearity range are highly desirable. Herein, a simple and low-cost method for the fabrication of a flexible piezoresistive pressure sensor with a hierarchical structure over large areas is presented. The piezoresistive pressure sensor consists of arrays of microscale papillae with nanoscale roughness produced by replicating the lotus leaf's surface and spray-coating of graphene ink. Finite element analysis (FEA) shows that the hierarchical structure governs the deformation behavior and pressure distribution at the contact interface, leading to a quick and steady increase in contact area with loads. As a result, the piezoresistive pressure sensor demonstrates a high sensitivity of 1.2 kPa and a wide linearity range from 0 to 25 kPa. The flexible pressure sensor is applied for sensitive monitoring of small vibrations, including wrist pulse and acoustic waves. Moreover, a piezoresistive pressure sensor array is fabricated for mapping the spatial distribution of pressure. These results highlight the potential applications of the flexible piezoresistive pressure sensor for health monitoring and electronic skin.