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Register a new userVersatile Graphene-Based Platform for Robust Nanobiohybrid Interfaces
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Added by
Jose Ignacio Martinez
Publication date
2019
fields
Physics
and research's language is
English
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Technologically useful and robust graphene-based interfaces for devices require the introduction of highly selective, stable, and covalently bonded functionalities on the graphene surface, whilst essentially retaining the electronic properties of the pristine layer. This work demonstrates that highly controlled, ultrahigh vacuum covalent chemical functionalization of graphene sheets with a thiol-terminated molecule provides a robust and tunable platform for the development of hybrid nanostructures in different environments. We employ this facile strategy to covalently couple two representative systems of broad interest: metal nanoparticles, via S-metal bonds, and thiol-modified DNA aptamers, via disulfide bridges. Both systems, which have been characterized by a multi-technique approach, remain firmly anchored to the graphene surface even after several washing cycles. Atomic force microscopy images demonstrate that the conjugated aptamer retains the functionality required to recognize a target protein. This methodology opens a new route to the integration of high-quality graphene layers into diverse technological platforms, including plasmonics, optoelectronics, or biosensing. With respect to the latter, the viability of a thiol-functionalized chemical vapor deposition graphene-based solution-gated field-effect transistor array was assessed.
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Porous, atomically thin graphene membranes have interesting properties for filtration and sieving applications because they can accommodate small pore sizes, while maintaining high permeability. These membranes are therefore receiving much attention for novel gas and water purification applications. Here we show that the atomic thickness and high resonance frequency of porous graphene membranes enables an effusion based gas sensing method that distinguishes gases based on their molecular mass. Graphene membranes are used to pump gases through nanopores using optothermal forces. By monitoring the time delay between the actuation force and the membrane mechanical motion, the permeation time-constants of various gases are shown to be significantly different. The measured linear relation between the effusion time constant and the square root of the molecular mass provides a method for sensing gases based on their molecular mass. The presented microscopic effusion based gas sensor can provide a small, low-power alternative for large, high-power, mass-spectrometry and optical spectrometry based gas sensing methods.
The use of natural or bioinspired materials to develop edible electronic devices is a potentially disruptive technology that can boost point-of-care testing. The technology exploits devices which can be safely ingested, along with pills or even food, and operated from within the gastrointestinal tract. Ingestible electronics could potentially target a significant number of biomedical applications, both as therapeutic and diagnostic tool, and this technology may also impact the food industry, by providing ingestible or food-compatible electronic tags that can smart track goods and monitor their quality along the distribution chain. We hereby propose temporary tattoo-paper as a simple and versatile platform for the integration of electronics onto food and pharmaceutical capsules. In particular, we demonstrate the fabrication of all-printed Organic Field-Effect Transistors (OFETs) on untreated commercial tattoo-paper, and their subsequent transfer and operation on edible substrates with a complex non-planar geometry.
Controlled atomic scale fabrication of functional devices is one of the holy grails of nanotechnology. The most promising class of techniques that enable deterministic nanodevice fabrication are based on scanning probe patterning or surface assembly. However, this typically involves a complex process flow, stringent requirements for an ultra high vacuum environment, long fabrication times and, consequently, limited throughput and device yield. Here, a device platform is developed that overcomes these limitations by integrating scanning probe based dopant device fabrication with a CMOS-compatible process flow. Silicon on insulator substrates are used featuring a reconstructed Si(001):H surface that is protected by a capping chip and has pre-implanted contacts ready for scanning tunneling microscope (STM) patterning. Processing in ultra-high vacuum is thus reduced to only a few critical steps which minimizes the complexity, time and effort required for fabrication of the nanoscale dopant devices. Subsequent reintegration of the samples into the CMOS process flow not only simplifies the post-processing but also opens the door to successful application of STM based dopant devices as a building block in more complex device architectures. Full functionality of this approach is demonstrated with magnetotransport measurements on degenerately doped STM patterned Si:P nanowires up to room temperature.
The high flexibility, impermeability and strength of graphene membranes are key properties that can enable the next generation of nanomechanical sensors. However, for capacitive pressure sensors the sensitivity offered by a single suspended graphene membrane is too small to compete with commercial sensors. Here, we realize highly sensitive capacitive pressure sensors consisting of arrays of nearly ten thousand small, freestanding double-layer graphene membranes. We fabricate large arrays of small diameter membranes using a procedure that maintains the superior material and mechanical properties of graphene, even after high-temperature anneals. These sensors are readout using a low cost battery-powered circuit board, with a responsivity of up to 47.8 aF Pa$^{-1}$ mm$^{-2}$, thereby outperforming commercial sensors.
Resistive-switching memories are alternative to Si-based ones, which face scaling and high power consumption issues. Tetrahedral amorphous carbon (ta-C) shows reversible, non-volatile resistive switching. Here we report polarity independent ta-C resistive memory devices with graphene-based electrodes. Our devices show ON/OFF resistance ratios$sim$4x$10^5$, ten times higher than with metal electrodes, with no increase in switching power, and low power density$sim$14$mu$W/$mu$m$^2$. We attribute this to a suppressed tunneling current due to the low density of states of graphene near the Dirac point, consistent with the current-voltage characteristics derived from a quantum point contact model. Our devices also have multiple resistive states. This allows storing more than one bit per cell. This can be exploited in a range of signal processing/computing-type operations, such as implementing logic, providing synaptic and neuron-like mimics, and performing analogue signal processing in non-von-Neumann architectures
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