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Bruno Michel

Bio: Bruno Michel is an academic researcher from IBM. The author has contributed to research in topics: Heat transfer & Thermal resistance. The author has an hindex of 69, co-authored 419 publications receiving 19281 citations. Previous affiliations of Bruno Michel include University of Zurich & Fraunhofer Society.


Papers
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Journal ArticleDOI
TL;DR: The International Nanofluid Property Benchmark Exercise (INPBE) as mentioned in this paper was held in 1998, where the thermal conductivity of identical samples of colloidally stable dispersions of nanoparticles or "nanofluids" was measured by over 30 organizations worldwide, using a variety of experimental approaches, including the transient hot wire method, steady state methods, and optical methods.
Abstract: This article reports on the International Nanofluid Property Benchmark Exercise, or INPBE, in which the thermal conductivity of identical samples of colloidally stable dispersions of nanoparticles or “nanofluids,” was measured by over 30 organizations worldwide, using a variety of experimental approaches, including the transient hot wire method, steady-state methods, and optical methods. The nanofluids tested in the exercise were comprised of aqueous and nonaqueous basefluids, metal and metal oxide particles, near-spherical and elongated particles, at low and high particle concentrations. The data analysis reveals that the data from most organizations lie within a relatively narrow band (±10% or less) about the sample average with only few outliers. The thermal conductivity of the nanofluids was found to increase with particle concentration and aspect ratio, as expected from classical theory. There are (small) systematic differences in the absolute values of the nanofluid thermal conductivity among the various experimental approaches; however, such differences tend to disappear when the data are normalized to the measured thermal conductivity of the basefluid. The effective medium theory developed for dispersed particles by Maxwell in 1881 and recently generalized by Nan et al. [J. Appl. Phys. 81, 6692 (1997)], was found to be in good agreement with the experimental data, suggesting that no anomalous enhancement of thermal conductivity was achieved in the nanofluids tested in this exercise.

942 citations

Journal ArticleDOI
02 May 1997-Science
TL;DR: The microfluidic networks used to pattern biomolecules with high resolution on a variety of substrates suggest a practical way to incorporate biological material on technological substrates.
Abstract: Microfluidic networks (microFNs) were used to pattern biomolecules with high resolution on a variety of substrates (gold, glass, or polystyrene). Elastomeric microFNs localized chemical reactions between the biomolecules and the surface, requiring only microliters of reagent to cover square millimeter-sized areas. The networks were designed to ensure stability and filling of the microFN and allowed a homogeneous distribution and robust attachment of material to the substrate along the conduits in the microFN. Immunoglobulins patterned on substrates by means of microFNs remained strictly confined to areas enclosed by the network with submicron resolution and were viable for subsequent use in assays. The approach is simple and general enough to suggest a practical way to incorporate biological material on technological substrates.

818 citations

Journal ArticleDOI
Heinz Schmid1, Bruno Michel1
TL;DR: In this article, the authors report the formulation of siloxane polymers for high-resolution, high-accuracy stamps for soft lithography, using models of rubber-like elasticity as guidelines.
Abstract: We report the formulation of siloxane polymers for high-resolution, high-accuracy stamps for soft lithography. With this technique, a molecular, polymeric, or liquid ink is applied to the surface of a stamp and then transferred by conformal contact to a substrate. Stamps for this technique are usually made of a commercial siloxane elastomer with appropriate mechanical properties to achieve conformal contact but are incapable of printing accurate, submicrometer patterns. To formulate better stamp polymers, we used models of rubber-like elasticity as guidelines. Poly(dimethylsiloxane) networks were prepared from vinyl and hydrosilane end-linked polymers and vinyl and hydrosilane copolymers, with varying mass between cross-links and junction functionality. The polymer formulations were characterized by strain at break as well as compression modulus and surface hardness measurements. This resulted in the identification of bimodal polymer networks having mechanical properties that allow the replication of high...

716 citations

Journal ArticleDOI
11 Apr 1998-Langmuir
TL;DR: Microcontact printing of proteins proves to be an excellent means of directly patterning biomolecules on solid substrates for the transfer of proteins of many different types onto hydrophilic or hydrophobic substrates.
Abstract: Microcontact printing of proteins proves to be an excellent means of directly patterning biomolecules on solid substrates. Monolayer quantities of protein equilibrated on the surface of a hydrophobic, elastomeric stamp are immobilized there to rinses with buffer. These biomolecules can nevertheless transfer with >99% efficiency from the stamp to a substrate after just 1 s of contact. This capability allows the simple creation of functional patterns of proteins at scales that involve the placement of <1000 molecules in well-defined locations on a surface. The method is suited for the transfer of proteins of many different types onto hydrophilic or hydrophobic substrates.

567 citations

Journal ArticleDOI
TL;DR: Surface-bound mole-cules find application in biosensors, chromatography, diagnos-tic immunoassays, cell culturing, DNA microarrays, and otheranalytical procedures and are driving efforts to minia-turize biological assays and to conduct many assays in paral-lel.
Abstract: Surface-bound mole-cules find application in biosensors, chromatography, diagnos-tic immunoassays, cell culturing, DNA microarrays, and otheranalytical procedures. Among these applications, diagnosticimmunoassays and DNA sensing are driving efforts to minia-turize biological assays and to conduct many assays in paral-lel. This trend offers several advantages. In small volumes,biochemical reactions may not be diffusion-limited and maythus be more efficient; less reagent and sample solution areused, lowering costs per test.

559 citations


Cited by
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01 May 1993
TL;DR: Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems.
Abstract: Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

29,323 citations

Journal ArticleDOI
TL;DR: Monolayers of alkanethiolates on gold are probably the most studied SAMs to date and offer the needed design flexibility, both at the individual molecular and at the material levels, and offer a vehicle for investigation of specific interactions at interfaces, and of the effect of increasing molecular complexity on the structure and stability of two-dimensional assemblies.
Abstract: The field of self-assembled monolayers (SAMs) has witnessed tremendous growth in synthetic sophistication and depth of characterization over the past 15 years.1 However, it is interesting to comment on the modest beginning and on important milestones. The field really began much earlier than is now recognized. In 1946 Zisman published the preparation of a monomolecular layer by adsorption (self-assembly) of a surfactant onto a clean metal surface.2 At that time, the potential of self-assembly was not recognized, and this publication initiated only a limited level of interest. Early work initiated in Kuhn’s laboratory at Gottingen, applying many years of experience in using chlorosilane derivative to hydrophobize glass, was followed by the more recent discovery, when Nuzzo and Allara showed that SAMs of alkanethiolates on gold can be prepared by adsorption of di-n-alkyl disulfides from dilute solutions.3 Getting away from the moisture-sensitive alkyl trichlorosilanes, as well as working with crystalline gold surfaces, were two important reasons for the success of these SAMs. Many self-assembly systems have since been investigated, but monolayers of alkanethiolates on gold are probably the most studied SAMs to date. The formation of monolayers by self-assembly of surfactant molecules at surfaces is one example of the general phenomena of self-assembly. In nature, self-assembly results in supermolecular hierarchical organizations of interlocking components that provides very complex systems.4 SAMs offer unique opportunities to increase fundamental understanding of self-organization, structure-property relationships, and interfacial phenomena. The ability to tailor both head and tail groups of the constituent molecules makes SAMs excellent systems for a more fundamental understanding of phenomena affected by competing intermolecular, molecular-substrates and molecule-solvent interactions like ordering and growth, wetting, adhesion, lubrication, and corrosion. That SAMs are well-defined and accessible makes them good model systems for studies of physical chemistry and statistical physics in two dimensions, and the crossover to three dimensions. SAMs provide the needed design flexibility, both at the individual molecular and at the material levels, and offer a vehicle for investigation of specific interactions at interfaces, and of the effect of increasing molecular complexity on the structure and stability of two-dimensional assemblies. These studies may eventually produce the design capabilities needed for assemblies of three-dimensional structures.5 However, this will require studies of more complex systems and the combination of what has been learned from SAMs with macromolecular science. The exponential growth in SAM research is a demonstration of the changes chemistry as a disciAbraham Ulman was born in Haifa, Israel, in 1946. He studied chemistry in the Bar-Ilan University in Ramat-Gan, Israel, and received his B.Sc. in 1969. He received his M.Sc. in phosphorus chemistry from Bar-Ilan University in 1971. After a brief period in industry, he moved to the Weizmann Institute in Rehovot, Israel, and received his Ph.D. in 1978 for work on heterosubstituted porphyrins. He then spent two years at Northwestern University in Evanston, IL, where his main interest was onedimensional organic conductors. In 1985 he joined the Corporate Research Laboratories of Eastman Kodak Company, in Rochester, NY, where his research interests were molecular design of materials for nonlinear optics and self-assembled monolayers. In 1994 he moved to Polytechnic University where he is the Alstadt-Lord-Mark Professor of Chemistry. His interests encompass self-assembled monolayers, surface engineering, polymers at interface, and surfaces phenomena. 1533 Chem. Rev. 1996, 96, 1533−1554

7,465 citations

Journal ArticleDOI
TL;DR: A procedure that makes it possible to design and fabricate microfluidic systems in an elastomeric material poly(dimethylsiloxane) (PDMS) in less than 24 h by fabricating a miniaturized capillary electrophoresis system is described.
Abstract: This paper describes a procedure that makes it possible to design and fabricate (including sealing) microfluidic systems in an elastomeric materialpoly(dimethylsiloxane) (PDMS)in less than 24 h. A network of microfluidic channels (with width >20 μm) is designed in a CAD program. This design is converted into a transparency by a high-resolution printer; this transparency is used as a mask in photolithography to create a master in positive relief photoresist. PDMS cast against the master yields a polymeric replica containing a network of channels. The surface of this replica, and that of a flat slab of PDMS, are oxidized in an oxygen plasma. These oxidized surfaces seal tightly and irreversibly when brought into conformal contact. Oxidized PDMS also seals irreversibly to other materials used in microfluidic systems, such as glass, silicon, silicon oxide, and oxidized polystyrene; a number of substrates for devices are, therefore, practical options. Oxidation of the PDMS has the additional advantage that it ...

5,491 citations

Journal ArticleDOI
07 Apr 2000-Science
TL;DR: An extension to the soft lithography paradigm, multilayersoft lithography, with which devices consisting of multiple layers may be fabricated from soft materials is described, to build active microfluidic systems containing on-off valves, switching valves, and pumps entirely out of elastomer.
Abstract: Soft lithography is an alternative to silicon-based micromachining that uses replica molding of nontraditional elastomeric materials to fabricate stamps and microfluidic channels. We describe here an extension to the soft lithography paradigm, multilayer soft lithography, with which devices consisting of multiple layers may be fabricated from soft materials. We used this technique to build active microfluidic systems containing on-off valves, switching valves, and pumps entirely out of elastomer. The softness of these materials allows the device areas to be reduced by more than two orders of magnitude compared with silicon-based devices. The other advantages of soft lithography, such as rapid prototyping, ease of fabrication, and biocompatibility, are retained.

4,218 citations