Nanotechnology

Transfer printing of sub-100 nm nanoparticles by soft lithography with solvent mediation

Abstract

In this paper we present an alternative approach to transfer-print controlled arrays of sub-100 nm gold nanoparticles onto a substrate with high placement accuracy. First, the assembly of gold nanoparticles is achieved on a topologically nanopatterned polydimethylsiloxane stamp through a convective and capillary assembly technique. Second, the dry particles assembly is subsequently printed from the plate onto plane substrates by contact through a thin film of liquid. We demonstrate that microcontact printing can be performed with solvent mediation for a high precision transfer of sub-100 nm individual particles and we discuss the most appropriate solvent. The transferred particles preserve their organization and physical properties.

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Transfer printing of sub-100 nm nanoparticles by soft lithography with solvent mediation

Nanomechanical Properties of Dead or Alive Single-Patterned Bacteria

Abstract

The main goal of this paper is to probe mechanical properties of living and dead bacteria via atomic force microscopy (AFM) indentation experimentations. Nevertheless, the prerequisite for bioAFM study is the adhesion of the biological sample on a surface. Although AFM has now been used in microbiology for 20 years, the immobilization of micro-organisms is still challenging. Immobilizing a single cell, without the need for chemical fixation has therefore constituted our second purpose. Highly ordered arrays of single living bacteria were generated over the millimeter scale by selective adsorption of bacteria onto micrometric chemical patterns. The chemically engineered template surfaces were prepared with a microcontact printing process, and different functionalizations of the patterns by incubation were investigated. Thanks to this original immobilization strategy, the Young moduli of the same cell were measured using force spectroscopy before and after heating (45 °C, 20 min). The cells with a damaged membrane (after heating) present a Young modulus twice as high as that of healthy bacteria.

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Nanomechanical Properties of Dead or Alive Single-Patterned Bacteria

Micro-Contact Printing of different biomolecules in one step using deformable Poly(dimethylsiloxane)-based stamps

Abstract

Patterning biomolecules at the micron or nano-scale presents a major challenge for the elaboration of integrated biochips. Among the different techniques that are emerging, Microcontact printing (µCP) appears as one of the most promising due to its simplicity and low cost. However, µCP exhibits a severe limitation because only one type of molecule can be deposited at a time using a poly(dimethyldiloxane) (PDMS) stamp. We present a new process called one-step-multiple-µCP (OSM-µCP) using a specific multilevel PDMS stamp which allows the patterning of two different molecules in one step. Our method based on the elastomeric properties of a PDMS stamp can print self aligned patterns of two different molecules by pressuring homogenously the top side of the stamp. The stamp levels inked by two different molecules contact the surface sequentially. OSM-µCP of two proteins, here bovin serum albumin BSA and streptavidin is demonstrated and this method can be applied to others couples of molecules. These results show that patterning biomolecules with OSM-µCP process opens new perspectives for soft lithography by enabling the fabrication of complex patterns of different molecules. .

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Micro-Contact Printing of different biomolecules in one step using deformable Poly(dimethylsiloxane)-based stamps

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