Showing papers by "Ralph G. Nuzzo published in 2007"

Optical systems fabricated by printing-based assembly

Abstract: Provided are optical devices and systems fabricated, at least in part, via printing-based assembly and integration of device components. In specific embodiments the present invention provides light emitting systems, light collecting systems, light sensing systems and photovoltaic systems comprising printable semiconductor elements, including large area, high performance macroelectronic devices. Optical systems of the present invention comprise semiconductor elements assembled, organized and/or integrated with other device components via printing techniques that exhibit performance characteristics and functionality comparable to single crystalline semiconductor based devices fabricated using conventional high temperature processing methods. Optical systems of the present invention have device geometries and configurations, such as form factors, component densities, and component positions, accessed by printing that provide a range of useful device functionalities. Optical systems of the present invention include devices and device arrays exhibiting a range of useful physical and mechanical properties including flexibility, shapeability, conformability and stretchablity.

Competing fracture in kinetically controlled transfer printing.

Abstract: Transfer printing by kinetically switchable adhesion to an elastomeric stamp shows promise as a powerful micromanufacturing method to pickup microstructures and microdevices from the donor substrate and to print them to the receiving substrate. This can be viewed as the competing fracture of two interfaces. This paper examines the mechanics of competing fracture in a model transfer printing system composed of three laminates: an elastic substrate, an elastic thin film, and a viscoelastic member (stamp). As the system is peeled apart, either the interface between the substrate and thin film fails or the interface between the thin film and the stamp fails. The speed-dependent nature of the film/stamp interface leads to the prediction of a critical separation velocity above which separation occurs between the film and the substrate (i.e., pickup) and below which separation occurs between the film and the stamp (i.e., printing). Experiments verify this prediction using films of gold adhered to glass, and the theoretical treatment extends to consider the competing fracture as it applies to discrete micro-objects. Temperature plays an important role in kinetically controlled transfer printing with its influences, making it advantageous to pickup printable objects at the reduced temperatures and to print them at the elevated ones.

Release Strategies for Making Transferable Semiconductor Structures, Devices and Device Components

Abstract: Provided are methods for making a device or device component by providing a multilayer structure having a plurality of functional layers and a plurality of release layers and releasing the functional layers from the multilayer structure by separating one or more of the release layers to generate a plurality of transferable structures. The transferable structures are printed onto a device substrate or device component supported by a device substrate. The methods and systems provide means for making high-quality and low-cost photovoltaic devices, transferable semiconductor structures, (opto-)electronic devices and device components.

Controlled buckling structures in semiconductor interconnects and nanomembranes for stretchable electronics

Abstract: In an aspect, the present invention provides stretchable, and optionally printable, components such as semiconductors and electronic circuits capable of providing good performance when stretched, compressed, flexed or otherwise deformed, and related methods of making or tuning such stretchable components. Stretchable semiconductors and electronic circuits preferred for some applications are flexible, in addition to being stretchable, and thus are capable of significant elongation, flexing, bending or other deformation along one or more axes. Further, stretchable semiconductors and electronic circuits of the present invention are adapted to a wide range of device configurations to provide fully flexible electronic and optoelectronic devices.

Microfluidic devices for culturing primary mammalian neurons at low densities

Abstract: Microfluidic devices have been used to study high-density cultures of many cell types. Because cell-to-cell signaling is local, however, there exists a need to develop culture systems that sustain small numbers of neurons and enable analyses of the microenvironments. Such cultures are hard to maintain in stable form, and it is difficult to prevent cell death when using primary mammalian neurons. We demonstrate that postnatal primary hippocampal neurons from rat can be cultured at low densities within nanoliter-volume microdevices fabricated using polydimethylsiloxane (PDMS). Doing so requires an additional fabrication step, serial extractions/washes of PDMS with several solvents, which removes uncrosslinked oligomers, solvent and residues of the platinum catalyst used to cure the polymer. We found this step improves the biocompatibility of the PDMS devices significantly. Whereas neurons survive for ≥ 7 days in open channel microdevices, the ability to culture neurons in closed-channel devices made of untreated, native PDMS is limited to ≤ 2 days. When the closed-channel PDMS devices are extracted, biocompatibility improves allowing for reliable neuron cultures at low densities for ≥ 7 days. Comparisons made to autoclaved PDMS and native, untreated PDMS reveal that the solvent-treated polymer is superior in sustaining low densities of primary neurons in culture. When neuronal affinity for local substrates is observed directly, we find that axons localize to channel corners and prefer PDMS surfaces to glass in hybrid devices. When perfusing the channels with media by gravity flow, cultured hippocampal neurons survive for ≥ 11 days. Extracting PDMS improves biocompatibility of microfluidic devices and thus enables the study of differentiation of identifiable neurons and the characterization of local extracellular signals.

Bendable integrated circuits on plastic substrates by use of printed ribbons of single-crystalline silicon

Abstract: This letter presents studies of several simple integrated circuits—n-channel metal-oxide semiconductor inverters, five-stage ring oscillators, and differential amplifiers—formed on thin, bendable plastic substrates with printed ribbons of ultrathin single-crystalline silicon as the semiconductor. The inverters exhibit gains as high as 2.5, the ring oscillators operate with oscillation frequencies between 8 and 9MHz at low supply voltages (∼4V), and the differential amplifiers show good performance and voltage gains of 1.3 for 500mV input signals. The responses of these systems to bending-induced strains show that relatively moderate changes of individual transistors can be significant for the operation of circuits that incorporate many transistors.

Multispectral plasmonic crystal sensors

Abstract: The present invention provides plasmonic crystals comprising three-dimensional and quasi comprising three-dimensional distributions of metallic or semiconducting films, including multi-layered crystal structures comprising nanostructured films and film arrays. Plasmonic crystals of the present invention include precisely registered and deterministically selected nonplanar crystal geometries and spatial distributions providing highly coupled, localized plasmonic responses in thin film elements and/or nanostructures of the crystal. Coupling of plasmonic responses provided by three-dimensional and quasi-three dimensional plasmonic crystal geometries and structures of the present invention generates enhanced local plasmonic field distributions useful for detecting small changes in the composition of an external dielectric environment proximate to a sensing surface of the plasmonic crystal. Plasmonic crystal structures of the present invention are also useful for providing highly localized excitation and/or imaging of fluorophores proximate to the crystal surface.

Mass spectrometric imaging of peptide release from neuronal cells within microfluidic devices.

Abstract: Microfluidic devices are well suited for manipulating and measuring mass limited samples. Here we adapt a microfluidic device containing functionalized surfaces to chemically stimulate a small number of neurons (down to a single neuron), collect the release of neuropeptides, and characterize them using mass spectrometry. As only a small fraction of the peptides present in a neuron are released with physiologically relevant stimulations, the amount of material available for measurement is small, thereby requiring minimal sample loss and high-sensitivity detection. Although a number of detection schemes are used with microfluidic devices, mass spectrometric detection is used here because of its high information content, allowing the characterization of the released peptide complement. Rather than using an on-line approach, off-line analysis is used; after collection of the peptides onto a surface, mass spectrometric imaging interrogates that surface to determine the peptides released from the cell. The overall utility of this scheme is demonstrated using several device formats with measurement of neuropeptides released from Aplysia californica bag cell neurons.

Optical transduction of chemical forces

Abstract: We describe a plasmonic crystal device possessing utility for optically transducing chemical forces. The device couples complex plasmonic fields to chemical changes via a chemoresponsive, surface-bound hydrogel. We find that this architecture significantly enhances the spectroscopic responses seen at visible wavelengths while enabling capacities for sensitive signal transduction, even in cases that involve essentially no change in refractive index, thus allowing analytical detection via colorimetric assays in both imaging and spectroscopic modes.

Tangential ligand-induced strain in icosahedral Au13.

Abstract: A quantitative comparison of first principles calculations with extended X-ray absorption fine structure and transmission electron microscopy measurements provides strong evidence that Au13 nanocrystals are stabilized in a slightly distorted icosahedral structure by on-top phosphine ligands and a combination of on-top and bridging thiol ligands. Importantly, the ligands change the icosahedral strain (i.e., the radial−tangential bond length ratio) significantly, with the tangential bonds within the Au core exhibiting much more disorder than the radial ones.

Spatially resolved biosensing with a molded plasmonic crystal

Abstract: The authors report the use of a type of quasi-three-dimensional plasmonic crystal for spatially resolved detection of biochemical binding events, with a spatial resolution of tens of microns and submonolayer binding sensitivity. In demonstration experiments, fibrinogen patterns nonspecifically adsorbed to the crystal surface were spatially and spectroscopically resolved using monochromatic and white light illumination. The experimental simplicity of the fabrication and use of these sensors, their compact form factors together with the high detection sensitivities and spatial resolution that can be achieved, collectively make these devices interesting as candidates for label-free array-based bioanalytical detection.

Microfluidic device for the discrimination of single-nucleotide polymorphisms in DNA oligomers using electrochemically actuated alkaline dehybridization.

Abstract: This work describes an integrated microfluidic (μ-fl) device that can be used to effect separations that discriminate single-nucleotide polymorphisms (SNP) based on kinetic differences in the lability of perfectly matched (PM) and mismatched (MM) DNA duplexes during alkaline dehybridization For this purpose a 21-base single-stranded DNA (ssDNA) probe sequence was immobilized on agarose-coated magnetic beads, that in turn can be localized within the channels of a poly(dimethylsiloxane) microfluidic device using an embedded magnetic separator The PM and MM ssDNA targets were hybridized with the probe to form a mixture of PM and MM DNA duplexes using standard protocols, and the hydroxide ions necessary for mediating the dehybridization were generated electrochemically in situ by performing the oxygen reduction reaction (ORR) using O2 that passively permeates the device at a Pt working electrode (Pt-WE) embedded within the microfluidic channel system The alkaline DNA dehybridization process was followed us

Variably elastic hydrogel patterned via capillary action in microchannels

Abstract: Agarose hydrogels of varied elastic modulus can be patterned into 100-μm-wide channels with wall heights of 60 μm. After modifying the hydrogels with chloroacetic acid (acid gels), they are amenable to modification with amine-containing ligands using EDC-NHS chemistry. Using both rheometry and atomic force microscopy (AFM) nanoindentation measurements, the elastic modulus of unmodified hydrogels increases linearly from 3.6 ± 0.5 kPa to 45.2 ± 5.5 kPa for 0.5 to 2.0 wt/vol % hydrogel, respectively. The elastic modulus of acid gels is 2.2 ± 0.3 kPa to 16.2 ± 1.6 kPa for 0.5 to 2.0wt/vol %, respectively. No further changes were measured after further modifying the acid gels with fibronectin. Confocal images of rhodamine-modified acid gels show that the optimal filling viscosity of the agarose solutions is between 1 and 4 cP. This new method of patterning allows for the creation of substrates that take advantage of both micron-scale patterns and variably elastic hydrogels.

Adsorption of linear alkanes on Cu(111): temperature and chain-length dependence of the softened vibrational mode.

Abstract: The vibrational spectra of linear alkanes, with lengths ranging from n-propane to n-octane, were examined on a copper surface by reflection-absorption infrared spectroscopy. The appearance and frequency of the “soft mode,” a feature routinely seen in studies of saturated hydrocarbons adsorbed on metals, were examined and compared between the different adsorbates. The frequency of the mode was found to be dependent on both the number of methylene units of each alkane as well as specific aspects of the order of the monolayer phase. Studies of monolayer coverages at different temperatures provide insights into the nature of the two-dimensional (2D) melting transitions of these adlayer structures, ones that can be inferred from observed shifts in the soft vibrational modes appearing in the C–H stretching region of the infrared spectrum. These studies support recently reported hypotheses as to the origins of such soft modes: the metal-hydrogen interactions that mediate them and the dynamics that underlay their...

Geometry and Charge State of Mixed-Ligand Au13 Nanoclusters

Abstract: The integration of synthetic, experimental and theoretical tools into a self‐consistent data analysis methodology allowed us to develop unique new levels of detail in nanoparticle characterization We describe our methods using an example of Au13 monolayer‐protected clusters (MPCs), synthesized by ligand exchange methods The combination of atom counting methods of scanning transmission electron microscopy and Au L3‐edge EXAFS allowed us to characterize these clusters as icosahedral, with surface strain reduced from 5% (as in ideal, regular icosahedra) to 3%, due to the interaction with ligands Charge transfer from Au to the thiol and phosphine ligands was evidenced by S and P K‐edge XANES A comparison of total energies of bare clusters of different geometries was performed by equivalent crystal theory calculations

Pattern transfer printing by dynamic control of adhesion on elastomer stamp

Abstract: PROBLEM TO BE SOLVED: To provide a method to transfer, assemble and integrate components and component arrays with physical dimensions of selected nano and/or micro sizes, shapes and space orientation, systems and system components. SOLUTION: In order to provide a guide to transfer, assemble and/or integrate printable components such as semiconductor elements, other electronic device components, and the like; the principle of "soft adhesion" is used. Components are transferred from a donor substrate to the transfer surface of an elastomer transfer device, and in some cases from the surface of the elastomer transfer device to the receiving surface of a receiving substrate. Using the method and system, an extremely efficient register transfer of printable components and component arrays such as semiconductor elements and the like can be performed by a cooperative method, by which the relative space orientation of transfer components can be maintained. COPYRIGHT: (C)2007,JPO&INPIT

Quantitative Studies of Au Nano-Catalysts by STEM and HRTEM

Abstract: Extended abstract of a paper presented at Microscopy and Microanalysis 2007 in Ft. Lauderdale, Florida, USA, August 5 – August 9, 2007

Quantitative STEM and HRTEM Studies on Au Metallic Nano-Catalysts

Abstract: Indium antimony (InSb) has been deformed in compression under gaseous confining pressure (Paterson apparatus) above and below the brittle to ductile transition occurring around 150°C. Thin foils have been prepared from the deformed samples and dislocations were characterized with conventional TEM as well as LACBED. This paper focuses on the room temperature deformation microstructures which appeared to be extremely complex with the observation of very well arranged network of perfect and partial dislocations. In such case, the traditional dislocation extinction conditions were extremely difficult to apply and only the use of the LACBED technique uncovered the nature of the observed dislocations and gave further insight to their interactions, revealing in particular the presence of partial dislocation dipoles. These original observations suggest a change of deformation mechanism at the brittle to ductile transition temperature.