DNA Translocation through Graphene Nanopores

Nanopores -- nanosized holes that can transport ions and molecules -- are very promising devices for genomic screening, in particular DNA sequencing. Both solid-state and biological pores suffer from the drawback, however, that the channel constituting the pore is long, viz. 10-100 times the distance between two bases in a DNA molecule (0.5 nm for single-stranded DNA). Here, we demonstrate that it is possible to realize and use ultrathin nanopores fabricated in graphene monolayers for single-molecule DNA translocation. The pores are obtained by placing a graphene flake over a microsize hole in a silicon nitride membrane and drilling a nanosize hole in the graphene using an electron beam. As individual DNA molecules translocate through the pore, characteristic temporary conductance changes are observed in the ionic current through the nanopore, setting the stage for future genomic screening

Atomic-scale electron-beam sculpting of defect-free graphene nanostructures

In order to harvest the many promising properties of graphene in (electronic) applications, a technique is required to cut, shape or sculpt the material on a nanoscale without damage to its atomic structure, as this drastically influences the electronic properties of the nanostructure. Here, we reveal a temperature-dependent self-repair mechanism allowing damage-free atomic-scale sculpting of graphene using a focused electron beam. We demonstrate that by sculpting at temperatures above 600 {\deg}C, an intrinsic self-repair mechanism keeps the graphene single-crystalline during cutting, even thought the electron beam induces considerable damage. Self-repair is mediated by mobile carbon ad-atoms constantly repairing the defects caused by the electron beam. Our technique allows reproducible fabrication and simultaneous imaging of single-crystalline free-standing nanoribbons, nanotubes, nanopores, and single carbon chains.Comment: 23 pages including supplementary informatio

Femto-Molar Sensitive Field Effect Transistor Biosensors Based on Silicon Nanowires and Antibodies

This article presents electrically-based sensors made of high quality silicon nanowire field effect transistors (SiNW- FETs) for high sensitive detection of vascular endothelial growth factor (VEGF) molecules. SiNW-FET devices, fabricated through an IC/CMOS compatible top-down approach, are covalently functionalized with VEGF monoclonal antibodies in order to sense VEGF. Increasing concentrations of VEGF in the femto molar range determine increasing conductance values as proof of occurring immuno-reactions at the nanowire (NW) surface. These results confirm data in literature about the possibility of sensing pathogenic factors with SiNW-FET sensors, introducing the innovating aspect of detecting biomolecules in dry conditions

SiNW-FET in-Air Biosensors for High Sensitive and Specific Detection in Breast Tumor Extract

The sensitive analysis of proteins is central to disease diagnosis. The detection and investigation of angiogenic and inflammatory ligands in the tumor tissue can further improve the level of knowledge of the cancer disease by capturing the heterogeneity and the complexity of the tumor microenvironment. In previous works we demonstrated that high quality Silicon Nanowire Field Effect Transistors (SiNW-FETs) can be used to sense very low concentration (fM) of pathogenic factors in controlled Phosphate Buffered Saline (PBS). In this work, we show SiNW-FETs as biosensors for the detection of cancer markers in tumor extracts, as proof of our technology to successfully work on real patients’ sample. In particular, we achieved the detection of exogenously added rabbit antigen in a much more complex environment, i.e. a human breast tumor extract. Our results show specific and high sensitive antigen detection with p-type SiNWFETs in the femto-molar range. Further and most importantly, the wires sense rabbit antigen molecules in the presence of a 100.000 mass excess of non-specific protein, indicating that the sensor is extremely resistant to noise

Surface Functionalization of SU-8 Vertical Waveguide for Biomedical Sensing: Bacteria Diagnosis

In this paper, we present an SU-8 based evanescent waveguide with a vertical structure as a biomedical sensor. The waveguide is designed vertically to generate evanescent waves on both left and right surfaces for sensing. It is fabricated by E-beam lithography with only one-step process which has the advantage of a better surface quality compared with commonly used dry etching methods. Furthermore, fabrication time and cost is cut down greatly. The surface of the designed waveguide can be functionalized with antibodies to immobilize specific bacteria on it. After surface functionalization and incubation with E. coli solutions of different concentrations, the waveguides absorption was measured. The results demonstrate that the waveguide is sensitive to E. coli concentration changes. In addition, tapers were designed and added to the waveguide to relieve the alignment tolerance for the aim of making a plug-and-play bedside diagnostic system

High Sensitive Detection in Tumor Extracts with SiNW-FET in-Air Biosensors

We have already demonstrated that high quality SiNW-FETs can be used to sense very low concentration range (fM) of pathogenic factors in controlled PBS. In this work we show, for the first time, Silicon Nanowire Field Effect Transistors (SiNW-FET) as biosensors for the detection of antigen in breast tumor extract. We achieved the detection of exogenously added rabbit antigen in a much more complex environment, i.e. a human breast tumor extract. Our preliminary results show specific antigen detection with SiNW-FETs in the range of 5-200 fM. Further and most importantly, the wires sense the antigen in the presence of a 100 000 mass excess of non-specific protein, indicating that the sensor is extremely resistant to noise