Nanotechnology

A simple and versatile micro contact printing method for generating carbon nanotubes patterns on various substrates

Abstract

We present an optimized process for generating at low cost, patterns of carbon nanotubes (CNTs) on a large variety of substrates through a simple micro contact printing method. This method meets the requirements for the integration of CNTs into microdevices, for applications in microelectronics (interconnects), flexible electronics (printed conductive electrodes) and biodevices (biosensors and biosystems for regenerative medicine). We have optimized a new method for inking PolyDiMethylSiloxane (PDMS) stamps with CNTs that turned out to improve significantly the quality of the printed features over large surfaces. This inking step is performed by adapting a spray-coating process leading to a dense and homogeneous coating of the stamp with a thin layer of CNTs. The printing step is performed using a solvent mediation, allowing us to pattern this thin layer of CNTs onto various substrates by contact through a thin film of liquid. We demonstrate that this soft and rapid methodology can lead to the realization of CNTs patterns with versatile geometries onto various substrates at the micron scale. Examples of applications for CNTs interconnects and flexible electronics are rapidly shown.

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A simple and versatile micro contact printing method for generating carbon nanotubes patterns on various substrates

Silicon nanomembranes for fingertip electronics

Abstract

We describe the use of semiconductor nanomaterials, advanced fabrication methods and unusual device designs for a class of electronics capable of integration onto the inner and outer surfaces of thin, elastomeric sheets in closed-tube geometries, specially formed for mounting on the fingertips. Multifunctional systems of this type allow electrotactile stimulation with electrode arrays multiplexed using silicon nanomembrane (Si NM) diodes, high-sensitivity strain monitoring with Si NM gauges, and tactile sensing with elastomeric capacitors. Analytical calculations and finite element modeling of the mechanics quantitatively capture the key behaviors during fabrication/assembly, mounting and use. The results provide design guidelines that highlight the importance of the NM geometry in achieving the required mechanical properties. This type of technology could be used in applications ranging from human–machine interfaces to ‘instrumented’ surgical gloves and many others.

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Silicon nanomembranes for fingertip electronics

Bifunctional Janus beads made by “sandwich” microcontact printing using click chemistry

Abstract

This article describes the preparation of spherical Janus particles by microcontact printing. A set of three different polymer beads (diameter ca. 170 μm), each bearing different functional groups at their surface, are used to covalently attach distinct functional molecules exclusively on opposing poles of the beads. The covalent modification of the beads involves three different types of click chemistry: epoxide ring opening (ERO), copper catalysed azide–alkyne cycloaddition (CuAAC) and thiol–yne addition (TYA). These reactions are compared with regard to their advantages and disadvantages in the context of “sandwich” microcontact chemistry. The success of surface modification of the beads is verified by fluorescence microscopy and 3D-time of flight secondary ion mass spectrometry measurements and is further supported by reference experiments on planar surfaces bearing the same surface functionality and analysed by X-ray photoelectron spectroscopy, secondary ion mass spectrometry, atomic force microscopy and fluorescence microscopy. Furthermore we demonstrate that sandwich microcontact printing can also be performed on smaller polymer beads with a diameter of ca. 5 μm. The broad scope of surface chemistry in combination with the simple experimental setup makes this method attractive to a wide range of material science applications, since it combines orthogonality of surface functionalization with high pattern fidelity.

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Bifunctional Janus beads made by “sandwich” microcontact printing using click chemistry

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