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we have fabricated transparent electronic devices based on graphene materials with thickness down to one single atomic layer by the transfer printing method. The resulting printed graphene devices retain high field effect mobility and have low contact resistance. The results show that the transfer printing method is capable of high-quality transfer of graphene materials from silicon dioxide substrates, and the method thus will have wide applications in manipulating and delivering graphene materials to desired substrate and device geometries. Since the method is purely additive, it exposes graphene (or other functional materials) to no chemical preparation or lithographic steps, providing greater experimental control over device environment for reproducibility and for studies of fundamental transport mechanisms. Finally, the transport properties of the graphene devices on the PET substrate demonstrate the non-universality of minimum conductivity and the incompleteness of the current transport theory.
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A well-defined insulating layer is of primary importance in the fabrication of passive (e.g. capacitors) and active (e.g. transistors) components in integrated circuits. One of the most widely known 2-Dimensional (2D) dielectric materials is hexagonal boron nitride (hBN). Solution-based techniques are cost-effective and allow simple methods to be used for device fabrication. In particular, inkjet printing is a low-cost, non-contact approach, which also allows for device design flexibility, produces no material wastage and offers compatibility with almost any surface of interest, including flexible substrates. In this work we use water-based and biocompatible graphene and hBN inks to fabricate all-2D material and inkjet-printed capacitors. We demonstrate an areal capacitance of 2.0 pm 0.3 nF cm^(-2) for a dielectric thickness of sim 3 mu m and negligible leakage currents, averaged across more than 100 devices. This gives rise to a derived dielectric constant of 6.1 pm 1.7. The inkjet printed hBN dielectric has a breakdown field of 1.9 pm 0.3 MV cm^(-1). Fully printed capacitors with sub-/mu m hBN layer thicknesses have also been demonstrated. The capacitors are then exploited in two fully printed demonstrators: a resistor-capacitor (RC) low-pass filter and a graphene-based field effect transistor.
Graphene was recently proposed as a material for heat removal owing to its extremely high thermal conductivity. We simulated heat propagation in silicon-on-insulator circuits with and without graphene lateral heat spreaders. Numerical solutions of the heat propagation equations were obtained using the finite element method. The analysis was focused on the prototype silicon-on-insulator circuits with the metal-oxide-semiconductor field-effect transistors. It was found that the incorporation of graphene or few-layer graphene layers with proper heat sinks can substantially lower the temperature of the localized hot spots. The maximum temperature in the transistor channels was studied as function of graphenes thermal conductivity and the thickness of the few-layer-graphene. The developed model and obtained results are important for the design of graphene heat spreaders and interconnects.
Manufacturing electronic devices by printing techniques with low temperature sintering of nano-size material particles can revolutionize the electronics industry in coming years. The impact of this change to the industry can be significant enabling low-cost products and flexibility in manufacturing. implementation of a new production technology with new materials requires thorough elementary knowledge creation. It should be noticed that although some of first electronic devices ideally can be manufactured by printing, at the present several modules are in fact manufactured by using hybrid techniques (for instance photolithography, vapor depositions, spraying, etc...).
Soft-elasticity in monodomain liquid crystal elastomers (LCEs) is promising for impact-absorbing applications where strain energy is ideally absorbed at constant stress. Conventionally, compressive and impact studies on LCEs have not been performed given the notorious difficulty synthesizing sufficiently large monodomain devices. Here we demonstrate 3D printing bulk ($>cm^3$) monodomain LCE devices using direct ink writing and study their compressive soft-elasticity over 8 decades of strain rate. At quasi-static rates, the monodomain soft-elastic LCE dissipated 45% of strain energy while comparator materials dissipated less than 20%. At strain rates up to $3000~s^{-1}$, our soft-elastic monodomain LCE consistently performed closest to an ideal-impact absorber. Drop testing reveals soft-elasticity as a likely mechanism for effectively reducing the severity of impacts -- with soft elastic LCEs offering a Gadd Severity Index 40% lower than a comparable isotropic elastomer. Lastly, we demonstrate tailoring deformation and buckling behavior in monodomain LCEs via the printed director orientation.
We developed a wideband quasi-optical band-pass filter covering 170-520 GHz by exploiting the recent advancements in commercially available flexible printed circuit (FPC) fabrication technologies. We designed and fabricated a three-layered stack of loaded hexagonal grid metal meshes using a copper pattern with a narrowest linewidth of $50~mumathrm{m}$ on a polyimide substrate. The measured frequency pass-band shape was successfully reproduced through a numerical simulation using a set of parameters consistent with the dimensions of the fabricated metal meshes. FPC-based metal mesh filters will provide a new pathway toward the on-demand development of millimeter/submillimeter-wave quasi-optical filters at low cost and with a short turnaround time.
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