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Biomedical subjects

John A Rogers

Publications and source records attributed to John A Rogers.

At least 19 recordsLinked to original sources
PubMed2006

Heterogeneous three-dimensional electronics by use of printed semiconductor nanomaterials.

We developed a simple approach to combine broad classes of dissimilar materials into heterogeneously integrated electronic systems with two- or three-dimensional layouts. The process begins with the synthesis of different semiconductor nanomaterials, such as single-walled carbon nanotubes and single-crystal micro- and nanoscale wires and ribbons of gallium nitride, silicon, and gallium arsenide on separate substrates. Repeated application of an additive, transfer printing process that uses soft stamps with these substrates as donors, followed by device and interconnect formation, yields high-performance heterogeneously integrated electronics that incorporate any combination of semiconductor nanomaterials on rigid or flexible device substrates. This versatile methodology can produce a wide range of unusual electronic systems that would be impossible to achieve with other techniques.

Journal Article↗
PubMed2006

Quantitative multispectral biosensing and 1D imaging using quasi-3D plasmonic crystals.

We developed a class of quasi-3D plasmonic crystal that consists of multilayered, regular arrays of subwavelength metal nanostructures. The complex, highly sensitive structure of the optical transmission spectra of these crystals makes them especially well suited for sensing applications. Coupled with quantitative electrodynamics modeling of their optical response, they enable full multiwavelength spectroscopic detection of molecular binding events with sensitivities that correspond to small fractions of a monolayer. The high degree of spatial uniformity of the crystals, formed by a soft nanoimprint technique, provides the ability to image binding events over large areas with micrometer spatial resolution. These features, together with compact form factors, low-cost fabrication procedures, simple readout apparatus, and ability for direct integration into microfluidic networks and arrays, suggest promise for these devices in label-free bioanalytical detection systems.

Avidin↗
PubMed2006

Combined confocal/en face T-scan-based ultrahigh-resolution optical coherence tomography in vivo retinal imaging.

Combined confocal scanning ophthalmoscopy/en face T-scan-based ultrahigh-resolution optical coherence tomography (OCT) of the human retina in vivo is reported for the first time to our knowledge. The system uses a superluminescent diode-based broadband source, which gives an axial resolution of 3.2 microm in the retina. We demonstrate acquisition of T-scan-based OCT B-scan and simultaneous confocal/C-scan images of the human retina of large lateral size (covering a field of up to 20 degrees ) at a frame rate of 2Hz.

Equipment Design↗
PubMed2006

Spatially selective guided growth of high-coverage arrays and random networks of single-walled carbon nanotubes and their integration into electronic devices.

The chemical vapor deposition growth of unusual arrangements of single-walled carbon nanotubes (SWNTs) by the combined of use patterned catalysts and quartz substrates is reported. Nearly perfectly aligned, high-coverage arrays of SWNTs can be generated in this manner. High-coverage random networks of SWNTs can also be created in the same growth step, with good spatial alignment and electrical interfaces to the aligned arrays. Tubes with these geometries are ideally suited to applications in thin-film electronic devices. We demonstrate this possibility through the construction of thin-film-type transistors in which the random networks form the source and drain electrodes and the aligned arrays form the channel.

Journal Article↗
PubMed2006

Bulk quantities of single-crystal silicon micro-/nanoribbons generated from bulk wafers.

This Letter demonstrates a strategy for producing bulk quantities of high quality, dimensionally uniform single-crystal silicon micro- and nanoribbons from bulk silicon (111) wafers. The process uses etched trenches with controlled rippled structures defined on the sidewalls, together with angled evaporation of masking materials and anisotropic wet etching of the silicon, to produce multilayer stacks of ribbons with uniform thicknesses and lithographically defined lengths and widths, across the entire surface of the wafer. Ribbons with thicknesses between tens and hundreds of nanometers, widths in the micrometer range, and lengths of up to several centimeters, can be produced, in bulk quantities, using this approach. Printing processes enable the layer by layer transfer of organized arrays of such ribbons to a range of other substrates. Good electrical properties (mobilities approximately 190 cm(2)V(-1)s(-1), on/off >10(4)) can be achieved with these ribbons in thin film type transistors formed on plastic substrates, thereby demonstrating one potential area of application.

Crystallization↗
PubMed2005

A stretchable form of single-crystal silicon for high-performance electronics on rubber substrates.

We have produced a stretchable form of silicon that consists of submicrometer single-crystal elements structured into shapes with microscale, periodic, wavelike geometries. When supported by an elastomeric substrate, this "wavy" silicon can be reversibly stretched and compressed to large levels of strain without damaging the silicon. The amplitudes and periods of the waves change to accommodate these deformations, thereby avoiding substantial strains in the silicon itself. Dielectrics, patterns of dopants, electrodes, and other elements directly integrated with the silicon yield fully formed, high-performance "wavy" metal oxide semiconductor field-effect transistors, p-n diodes, and other devices for electronic circuits that can be stretched or compressed to similarly large levels of strain.

Journal Article↗
PubMed2005

Organic nanodielectrics for low voltage carbon nanotube thin film transistors and complementary logic gates.

We report the implementation of three dimensionally cross-linked, organic nanodielectric multilayers as ultrathin gate dielectrics for a type of thin film transistor device that uses networks of single-walled carbon nanotubes as effective semiconductor thin films. Unipolar n- and p-channel devices are demonstrated by use of polymer coatings to control the behavior of the networks. Monolithically integrating these devices yields complementary logic gates. The organic multilayers provide exceptionally good gate dielectrics for these systems and allow for low voltage, low hysteresis operation. The excellent performance characteristics suggest that organic dielectrics of this general type could provide a promising path to SWNT-based thin film electronics.

Crystallography, X-Ray↗
PubMed2005

Electronically selective chemical functionalization of carbon nanotubes: correlation between Raman spectral and electrical responses.

Single-walled carbon nanotubes (SWNTs) demonstrate remarkable electronic and mechanical properties useful in developing areas such as nanoelectromechanical systems and flexible electronics. However, the highly inhomogeneous electronic distribution arising from different diameters and chirality in any given as-synthesized SWNT samples imposes severe limitations. Recently demonstrated selective chemical functionalization methods may provide a simple scalable means of eliminating metallic tubes from SWNT transistors and electronic devices. Here, we report on combined electron transport and Raman studies on the reaction of 4-bromobenzene diazonium tetrafluoroborate directly with single and networks of SWNT transistors. First, Raman studies are carried out on isolated individual SWNTs grown on SiO2/Si substrates by chemical vapor deposition with and without metal contacts. Metallic tubes are found to have, on average, higher reactivity toward diazonium reagents. However, a considerable degradation of electrical properties of semiconducting tubes occurs if the reaction is carried out to the point where the conductivity of metallic tubes is significantly suppressed. Insights from single-tube studies are then applied to elucidate the electrical and the Raman responses of SWNT random network transistors of different channel lengths to chemical functionalization.

Journal Article↗
PubMed2005

Stamp collapse in soft lithography.

We have studied the so-called roof collapse in soft lithography. Roof collapse is due to the adhesion between the PDMS stamp and substrate, and it may affect the quality of soft lithography. Our analysis accounts for the interactions of multiple punches and the effect of elastic mismatch between the PDMS stamp and substrate. A scaling law among the stamp modulus, punch height and spacing, and work of adhesion between the stamp and substrate is established. Such a scaling law leads to a simple criterion against the unwanted roof collapse. The present study agrees well with the experimental data.

Journal Article↗
PubMed2005

Optimization of distributed resistive metal film heaters in thermally tunable dispersion compensators for high-bit-rate communication systems.

Tunable dispersion compensators are an essential component for optical networks operating at 40 Gbits/s and beyond. One fiber-based tunable dispersion compensator that has proved to be effective consists of a chirped fiber Bragg grating tuned by a thin-film distributed resistive heating element. We describe several modifications to the heater design that minimize temperature-induced higher-order dispersion, eliminate the need for a second stabilization heater when the device is operated at constant ambient temperature, and significantly lower its maximum operating temperature. We demonstrate a tunable dispersion compensator with a single thin-film heater that provides over 500 ps/nm of tunable dispersion over a fixed 100-GHz bandwidth with a maximum operating temperature of less than 125 degrees C above ambient.

Journal Article↗
PubMed2005

Guided growth of large-scale, horizontally aligned arrays of single-walled carbon nanotubes and their use in thin-film transistors.

A convenient process for generating large-scale, horizontally aligned arrays of pristine, single-walled carbon nanotubes (SWNTs) is described. The approach uses guided growth, by chemical vapor deposition (CVD), of SWNTs on miscut single-crystal quartz substrates. Studies of the growth reveal important relationships between the density and alignment of the tubes, the CVD conditions, and the morphology of the quartz. Electrodes and dielectrics patterned on top of these arrays yield thin-film transistors that use the SWNTs as effective thin-film semiconductors. The ability to build high-performance devices of this type suggests significant promise for large-scale aligned arrays of SWNTs in electronics, sensors, and other applications.

Anisotropy↗
PubMed2005

Polymer electrolyte gating of carbon nanotube network transistors.

Network behavior in single-walled carbon nanotubes (SWNTs) is examined by polymer electrolyte gating. High gate efficiencies, low voltage operation, and the absence of hysteresis in polymer electrolyte gating lead to a convenient and effective method of analyzing transport in SWNT networks. Furthermore, the ability to control carrier type with chemical groups of the host polymer allows us to examine both electron and hole conduction. Comparison to back gate measurements is made on channel length scaling. Frequency measurements are also made giving an upper limit of approximately 300 Hz switching speed for poly(ethylene oxide)/LiClO(4) gated SWNT thin film transistors.

Electrochemistry↗
PubMed2005

Optically fabricated three dimensional nanofluidic mixers for microfluidic devices.

This paper describes a simple technique for fabricating complex, but well defined, three-dimensional (3D) networks of nanoscale flow paths in the channels of microfluidic systems. Near field scanning optical measurements reveal the optics associated with the fabrication process and the key features that enable its application to the area of microfluidics. Confocal studies of microfluidic devices that incorporate 3D nanostructures formed using this approach show that they function as efficient passive mixing elements, particularly at low Reynolds numbers. This application and others such as separation and extraction inmicrofluidic total analysis systems or lab on a chip devices represent promising areas for 3D nanostructures of this general type.

Equipment Design↗
PubMed2005

Additive soft-lithographic patterning of submicrometer- and nanometer-scale large-area resists on electronic materials.

We describe a novel soft-lithographic technique possessing broad utility for the fabrication of large area, nanoscale ( approximately 100 nm) multilayer resist structures on electronic material substrates. This additive patterning method transfers ultrathin poly(dimethylsiloxane) (PDMS) decals to an underlying SiO(2)-capped organic planarazation layer. The PDMS patterns serve as a latent image through which high-quality multilayer resist structures can be developed using reactive ion-beam etching.

Crystallization↗