Biomedical subjects

Babak A Parviz

Publications and source records attributed to Babak A Parviz.

6 recordsLinked to original sources

PubMed2006

Self-assembled single-crystal silicon circuits on plastic.

We demonstrate the use of self-assembly for the integration of freestanding micrometer-scale components, including single-crystal, silicon field-effect transistors (FETs) and diffusion resistors, onto flexible plastic substrates. Preferential self-assembly of multiple microcomponent types onto a common platform is achieved through complementary shape recognition and aided by capillary, fluidic, and gravitational forces. We outline a microfabrication process that yields single-crystal, silicon FETs in a freestanding, powder-like collection for use with self-assembly. Demonstrations of self-assembled FETs on plastic include logic inverters and measured electron mobility of 592 cm2/V-s. Finally, we extend the self-assembly process to substrates each containing 10,000 binding sites and realize 97% self-assembly yield within 25 min for 100-microm-sized elements. High-yield self-assembly of micrometer-scale functional devices as outlined here provides a powerful approach for production of macroelectronic systems.

Journal Article↗

PubMed2006

Integrated electronic detection of biomolecules.

Electronics offers several unique opportunities for the detection and characterization of biomolecules such as oligonucleotides and proteins. Solid-state microfabrication technology, similar to that used to make integrated circuits, can be employed to make integrated electronic sensing systems that are capable of simultaneously detecting multiple molecules. Here, we review some of the capabilities afforded by electronics for rapid and sensitive detection of biomolecules and discuss a recent demonstration of a multi-marker electronic sensing system for detection of uropathogens in clinical samples.

Biosensing Techniques↗

PubMed2006

Two-dimensional self-assembly of 1-pyrylphosphonic acid: transfer of stacks on structured surface.

Strong hydrogen bonding and pi-pi stacking between 1-pyrylphosphonic acid (PYPA) molecules were exploited to create self-assembled two-dimensional supramolecular structures. Polycrystalline films of these laminate crystalline PYPA bilayers were easily deposited onto the solid supports through a simple spin-coating technique. Atomic force microscopy (AFM), scanning tunneling microscopy (STM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), UV-vis absorption, and fluorescence spectroscopy reveal that processing parameters, such as solvent, concentration, and surface of the substrate, are critical factors in determining the final morphology of the stacked film. Robust laminate structures could be obtained only when short alkyl chain protic solvents (methanol or ethanol) and a nonhydrophobic substrate surface were used. Polycrystalline films were formed through the nucleation and growth of PYPA molecules into laminate structures at the air/solvent interface before they land on the substrate during the spin-coating process. These films possess good mechanical properties and were easily transferred onto a SiO2/Si substrate that was patterned with Au electrodes without breaking their crystalline structures. The successful transfer of the laminate crystals allows us to probe their electrical properties through a field effect transistor device. A gating effect on the charge transport of the stacked films indicates that PYPA laminate crystal possesses p-typed semiconductor characteristics.

Hydrogen Bonding↗

PubMed2006

Materials specificity and directed assembly of a gold-binding peptide.

Adsorption studies of a genetically engineered gold-binding peptide, GBP1, were carried out using a quartz-crystal microbalance (QCM) to quantify its molecular affinity to noble metals. The peptide showed higher adsorption onto and lower desorption from a gold surface compared to a platinum substrate. The material specificity, that is, the preferential adsorption, of GBP1 was also demonstrated using gold and platinum micropatterned on a silicon wafer containing native oxide. The biotinylated three-repeat units of GBP1 were preferentially adsorbed onto gold regions delineated using streptavidin-conjugated quantum dots (SAQDs). These experiments not only demonstrate that an inorganic-binding peptide could preferentially adsorb onto a metal (Au) rather than an oxide (SiO2) but also onto one noble metal (Au) over another (Pt). This result shows the utility of an engineered peptide as a molecular erector in the directed immobilization of a nanoscale hybrid entity (SAQDs) over selected regions (Au) on a fairly complex substrate (Au and Pt micropatterned regions on silica). The selective and controlled adsorption of inorganic-binding peptides may have significant implications in nano- and nanobiotechnology, where they could be genetically tailored for specific use in the development of self-assembled molecular systems.

Adsorption↗

PubMed2006

Subdiffraction photon guidance by quantum-dot cascades.

We report on a waveguide composed of a cascade of gain-enabled quantum dots with subwavelength dimensions. Fabrication is demonstrated through DNA-mediated self-assembly and a two-layer molecular self-assembly process that enables rapid prototyping. The device, which is identified with fluorescence microscopy and tested by optical near field detection, allows optical signal transfer at a well-defined wavelength in flexible routing geometry, such as straight paths and 90 degrees bends. The structure serves as a critical building block for nanophotonic systems with high integration density.

Adsorption↗

PubMed2005

Water-soluble sacrificial layers for surface micromachining.

This manuscript describes the use of water-soluble polymers for use as sacrificial layers in surface micromachining. Water-soluble polymers have two attractive characteristics for this application: 1) They can be deposited conveniently by spin-coating, and the solvent removed at a low temperature (95-150 degrees C), and 2) the resulting layer can be dissolved in water; no corrosive reagents or organic solvents are required. This technique is therefore compatible with a number of fragile materials, such as organic polymers, metal oxides and metals-materials that might be damaged during typical surface micromachining processes. The carboxylic acid groups of one polymer-poly(acrylic acid) (PAA)-can be transformed by reversible ion-exchange from water-soluble (Na+ counterion) to water-insoluble (Ca2+ counterion) forms. The use of PAA and dextran polymers as sacrificial materials is a useful technique for the fabrication of microstructures: Examples include metallic structures formed by the electrodeposition of nickel, and freestanding, polymeric structures formed by photolithography.

Acrylic Resins↗