Christophe Yamahata

The study of the electrical properties of DNA has aroused increasing interest since the last decade. So far, controversial arguments have been put forward to explain the electrical charge transport through DNA. Our experiments on DNA bundles manipulated with silicon-based actuated tweezers demonstrate undoubtedly that humidity is the main factor af...

In-plane linear displacements of microelectromechanical systems are measured with subnanometer accuracy by observing the periodic micropatterns with a charge-coupled device camera attached to an optical microscope. The translation of the microstructure is retrieved from the video by phase-shift computation using discrete Fourier transform analysis....

Flexible bearings are advantageous for microelectromechanical systems as they enable precise, accurate, repeatable, and reliable motion without frictional contact. Based on the principle of a rotary folded-beam suspension, we have designed, fabricated, modeled, and characterized an electrostatic rotary stepper micromotor in silicon. Using 3-D finit...

We investigate the tribological effects of multi-charged ion implantation (MCII) of nitrogen in CuZn39Pb3 alloy, a machinable brass that is widely used in the watchmaking industry. For this study, MCII of nitrogen was performed at 35 kV with a fluence of 5E17 atoms/cm^2 and has resulted in a threefold decrease of the coefficient of friction (COF),...

The spectral power distribution of a light-emitting diode (LED) has a distinctive asymmetrical gaussian shape. This is the macroscopic expression of finely tuned properties buried inside the semiconductor. In this white paper, we unveil why and how a photodiode can be used as a reliable radiometric instrument for the characterisation of broadband L...

The CIE chromaticity diagram is instrumental in colour theory. It is widely used to describe the performances of lightings or colour cameras, and more generally any tool aimed at faithfully reproducing colours as perceived by human vision. In this document, we show a practical use of this diagram through colour reproduction of the visible spectrum.

This technical guide is intended for those who want to deepen their knowledge on high-efficiency lighting systems without getting lost in the translation of datasheets. It could also appeal to anyone interested in LED-based technologies. The following topics are covered: telecentric lighting, collimation angle, homogenization optics, radiometric un...

Cost of ownership, ease of use and elimination of contaminating substances are important to R&D and manufacturing facilities using UV exposure tools. The Idonus UV-LED light engine provides solutions using your current UV optics for the retrofit of mercury arc lamp sources or with our optics new sources for mask aligners standalone light sources a...

Surface properties of biocompatible polymers (e.g., PEEK) play an extremely important role in their functionality. In the case of implants, the tribological properties of such materials including the coefficient of friction (COF) and their resistance to wear are crucial, since they influence heavily the application lifetime. Multi-charged Ion Impla...

Multi-charged Ion Implantation (MCII) enables the simultaneous implantation of ions having different charges (e.g., N + , N 2+ , N 3+ and N 4+ in the case of nitrogen) and hence, of different energy levels, resulting in a uniform penetration of ions over a wide range of depths. Ion implantation is well known for significantly improving surface prop...

Surface properties of biocompatible polymers (e.g. PEEK) play an extremely important role in their functionality. In the case of implants, the tribological properties of such materials including the coefficient of friction (COF) and their resistance to wear are crucial, since they influence heavily the application lifetime. Multi-Charged Ion Implan...

Multi-Charged Ion Implantation (MCII) enables the simultaneous implantation of ions having different charges (e.g., N+, N2+, N3+ and N4+ in the case of nitrogen) and consequently different energy levels, resulting in a uniform penetration of ions over a wide range of depths. Ion implantation is well known for significantly improving surface propert...

Reliable in vitro models are required to understand the ability of cells to respond and adapt to mechanical stimuli. To mimic and interface with the microenvironment, lab-on-a-chip devices and microelectromechanical systems (MEMS) provide excellent options. However, little effort has been done in combining them. To address this shortcoming, we have...

The GyroTracker is an optoelectronic watch timing machine that allows watch-testing laboratories to perform comprehensive analyzes of their mechanical movements in all measuring positions. The instrument performs real-time tracking of the balance wheel elongation to measure isochronism. The graphical user interface gives access to the instantaneous...

A simple optical method is proposed for performing in-plane experimental modal analysis of micromachined structures with a conventional charge-coupled device (CCD) camera. The motion of a micromechanical device actuated by high-frequency sinusoidal forces (kilohertz range) is recorded at the fixed sampling rate of a camera (typically, 28 frames/s)...

Characterization of DNA molecules by mechanical tweezers

We present a straightforward method for measuring in-plane linear displacements of microelectromechanical systems (MEMS) with subnanometer resolution. The technique is based on Fourier transform analysis of a video recorded with a Charge-Coupled Device (CCD) camera attached to an optical microscope and can be used to characterize any device featuri...

DNA manipulation based on dielectrophoresis between microfabricated electrodes is one of the most efficient methods for the physical handling of molecules. Dielectrophoresis is routinely used for stretching and trapping DNA molecules between the opposing tips of silicon nanotweezers. However, the precise number of trapped molecules is difficult to...

Poster presented during the 24th IEEE MEMS 2011 conference

This paper describes an integrated bio-reaction platform composed of silicon nanotweezers and open microfluidics for real time biomechanical assays. The silicon nanotweezers can sense slight biological modification of the trapped sample due to stable frequency response with high Q factor in liquid. The microfluidic device integrates active valves f...

We present a straightforward method for measuring in-plane linear displacements of microelectromechanical systems (MEMS) with a subnanometer resolution. The technique is based on Fourier transform analysis of a video recorded with a Charge-Coupled Device (CCD) camera attached to an optical microscope and can be used to characterize any device featu...

We present the design, modeling and characterization of a 3-phase electrostatic rotary stepper micromotor. The proposed motor is a monolithic device fabricated using silicon-on-insulator (SOI) technology. The rotor is suspended with a frictionless flexural pivot bearing and reaches an unprecedented rotational range of 30° (+/- 15°) at 65 V. We have...

We present a three-phase electrostatic rotary stepper micromotor for skew angle compensation of read/write heads in hard disk drives. The motor utilizes the electrical energy stored in the variable capacitances formed between the poles of a rotor and a stator. The rotor is suspended by a flexural suspension to avoid frictional contact during operat...

We developed a three-phase electrostatic stepper micromotor and performed a numerical simulation to improve its performance for practical use and to optimize its design. We conducted its circuit simulation by simplifying its structure, and the effect of springback force generated by supported mechanism using flexures was considered. And we consider...

Shuffle motors are electrostatic stepper micromotors that employ a built-in mechanical leverage to produce large output forces as well as high resolution displacements. These motors can generally move only over predefined paths that served as driving electrodes. Here, we present the design, modeling and experimental characterization of a novel shuf...

A 3-phase electrostatic stepper micromotor was developed. To improve its performance for actual use, we have conducted numerical simulation to optimize the design. An improved simulation method is needed for calculation of various cases. To conduct circuit simulation of this micromotor, its structure is simpli�ed, and a function for computing the f...

We developed a three-phase electrostatic stepper micromotor and performed a numerical simulation to improve its performance for practical use and to optimize its design. We conducted its circuit simulation by simplifying its structure, and the effect of springback force generated by supported mechanism using flexures was considered. And we consider...

Electrostatic stepper motors, also known as synchronous variable-capacitance motors, operate by utilizing the electrical energy stored in the variable capacitances formed between the poles of their rotor and stator. We present the design, modeling, and experimental characterization of a three-phase rotary stepper micromotor that employs a flexural...

A 3-phase electrostatic stepper micromotor was developed. To improve its performance for actual use, we have conducted numerical simulation to optimize the design. An improved simulation method is needed for calculation of various cases. To conduct circuit simulation of this micromotor, its structure is simplified, and a function for computing the...

In a hard disk drive, the angular alignment of the read/write head relative to a data track varies with the radial position of the track, increasing a risk of data track misregistration. We present a frictionless rotary micromotor which can be used as a secondary stage actuator to maintain a constant angle between the head and the tracks during dis...

We present the design, microfabrication and characterization of an electrostatic 3-phase linear stepper micromotor constructed with vertical trench isolation technology. This suitable technology was used to create a monolithic stepper motor with high-aspect-ratio poles and an integrated 3-phase electrical network in the bulk of a standard single-cr...

Molecular biophysicists seek to understand how biological systems work through mechanical or electrical characterizations performed at the molecular scale. From this perspective, we have devised a silicon-based micromechanical tool for stress-strain measurements of molecular fibers and demonstrated micro manipulation and biomechanical characterizat...

Circular data tracks in present-day hard disk drives (HDD) are accessed by a read/write head mounted on a support arm, which is swung by a voice coil drive. The orientation of the head relative to a data track varies with the radial position of the track, causing an increase in data track misregistration and limiting the performance of HDD. We pres...

We describe electrostatically actuated silicon nanotweezers which are intended for the manipulation and characterization of filamentary molecules. The microelectromechanical system consists of a pair of opposing tips whose distance can be accurately adjusted by means of an integrated differential capacitive sensor. The fabrication process is based...

We report a simple bulk micromachining method for the fabrication of high aspect ratio monocrystalline silicon MEMS (microelectromechanical systems) in a standard silicon wafer. We call this two-mask microfabrication process high aspect ratio etching and metallization or HAREM: it combines double-side etching and metallization to create suspended m...

In this study, we investigate improvements in silicon nanotweezers used to handle DNA molecules. We analyzed the deformation and frequency properties of the nanotweezers by finite element method (FEM) analysis. From this analysis, we determined the appropriate operation area of the nanotweezers.

We have fabricated and characterized a reciprocating poly(methylmetacrylate) (PMMA) ball-valve micropump actuated with a miniaturized cylindrical electromagnetic circuit. By finite element calculations, we have optimized the structure of the electromagnet that actuates a rare-earth permanent magnet embedded in a poly(dimethylsiloxane) (PDMS) pumpin...

MEMS tweezers to trap and manipulate bio molecules was fabricated. The gap size was controlled by KOH wet etching and Focused Ion beam process at the range from fifteen nanometers to twenty five micrometers to trap several different size of DNA molecules. We also fabricated the modified design of tweezers to successful trap of DNA, because thermal...

We describe a MEMS-based method for the biomechanical characterization of filamentary molecules. The system consists of a pair of electrostatically actuated silicon nanotweezers and a differential capacitive sensor that is connected to the moving tip of the tweezers. With such a tool, we achieved sub-nanometer displacement resolution (around 0.2 nm...

We report a novel bulk micromachining method for the fabrication of high aspect ratio monocrystalline silicon MicroElectroMechanical Systems (MEMS) on a standard silicon wafer. The two-mask process combines double-side etching and metallization to create a micromechanical system with 'insulating walls' on its backside. The insulating walls ensure a...

We present the microfabrication and characterization of a reciprocating-type poly(methylmetacrylate) (PMMA) ball-valve micropump which is actuated with a high-performance and compact electromagnetic circuit of centimeter size. We have improved by finite element calculations the magnetic design of the electromagnet that actuates a NdFeB permanent ma...

The cover picture shows a single DNA molecule trapped between floating aluminium electrodes by means of alternating current dielectrophoresis. The image was obtained by fluorescence microscopy using double-stranded lambda-phage DNA labelled with the YOYO-1 fluorescent dye. In their Article on page 1875 Kumemura et al. describe a method enabling the...

This paper presents a systematic method to isolate and trap long single DNA segments between integrated electrodes in a microfluidic environment. Double stranded lambda-DNA molecules are introduced in a microchip and are isolated by electrophoretic force through microfluidic channels. Downstream, each individual molecule is extended and oriented by...

This paper deals with the first simultaneous electrical and mechanical characterization of DNA bundles by a MEMS tool. The silicon-based device has an integrated actuator and a differential capacitive position sensor. Our experiments show that under constant humidity conditions, a rope of DNA has a nearly Ohmic conductivity and behaves as a viscoel...

Wet anisotropic etching of sharp silicon cavities is a critical step in the fabrication of nanopores and scanning probe tips. This paper reports a straightforward method to reliably obtain sharp pyramidal cavities in (1 0 0) oriented silicon wafers from a relatively inaccurate mask fabricated with a conventional laser exposure system. The relative...

Single-molecule micromanipulations have provided information that has been awaited for a long time. However, these experiments relying on optical tweezers (OT) or magnetic tweezers (MT) have a low throughput since the molecular preparation is done one at a time. In order to move towards systematic biological or medical analysis, micro-nano-electrom...

HBC nanotube bundle is trapped and mechanically tested by MEMS tweezers. HBC nanotube is macromolecule which has helical structure. Molecular Tweezers and Tweezers for Electron Microscopy (EM tweezers) is used for trapping HBC nanotube bundle. Dielectrophoresis is used for trapping by Molecular tweezers. Electron Microscopy observation is capable d...

We describe a simple method for the batch fabrication of solid-state pores with controllable size ranging from few micrometers down to few hundred nanometers. Based on our method, a ‘Coulter counter’ device was developed and we could demonstrate the straightforward detection of particles translocation through the pore, opening possibility for the d...

We describe electrostatically actuated silicon nanotweezers which are intended for the manipulation and characterization of DNA molecules. The fabrication process combines KOH etching and deep reactive ion etching (DRIE) on silicon-on-insulator (SOI) wafer to form sharp nanotips and high aspect ratio microstructures, respectively. The microelectrom...

We describe a simple method for the batch fabrication of solid-state pores with controllable size ranging from few micrometers down to few hundred nanometers. Based on our method, a 'Coulter counter' device was developed and we could demonstrate the straightforward detection of particles translocation through the pore, opening possibility for the d...

We discuss the successful transport of jurkat cells and 5D10 hybridoma cells using a reciprocating micropump with nozzle-diffuser elements. The effect of the pumping action on cell viability and proliferation, as well as on the damaging of cellular membranes is quantified using four types of well-established biological tests: a trypan blue solution...

We present the microfabrication and characterization of a ball valve micropump in glass, which is magnetically actuated using the sinusoidal current of an external electromagnet. We employ the use of a simple powder blasting technology for microstructuring the glass substrates and fusion bonding for assembly of the multi-layered microfluidic chip....

We present two types of oscillating diaphragm micropumps configured with passive ball valves and using electromagnetic actuation. One type is made out of poly(methyl methacrylate) (PMMA), while the other one is made out of borosilicate glass. Both were produced using the powder blasting microfabrication method. The pumping resonant frequency was me...

We have fabricated and characterized a polymethylmethacrylate (PMMA) valveless micropump. The pump consists of two diffuser elements and a polydimethylsiloxane (PDMS) membrane with an integrated composite magnet made of NdFeB magnetic powder. A large-stroke membrane deflection (~200 µm) is obtained using external actuation by an electromagnet. We p...

We present a valveless micropump in glass, which is magnetically actuated using the sinusoidal current of an external electromagnet. We employ a powder blasting microerosion process for microstructuring the glass substrates and fusion bonding for assembly of the multi-layered microfluidic chip. The reciprocating type micropump contains two nozzle/d...

Thèse no 3208 sc. EPF Lausanne. Literaturverz. EPFL, Lausanne

This paper presents a simple and low-cost prototyping technology for the realization of integrated micropumps in polymethylmethacrylate (PMMA). The three-dimensional (3D) micropumps consist of stacks of structured PMMA layers, which are either realised with precision milling tools for the more complex parts, or fabricated using the powder blasting...

A disposable micropump is presented that uses the piston actuation principle and relies on the magnetic properties of a ferrofluid, a colloidal suspension of nanosize ferromagnetic particles. The cost effective micropump consists of 7 bonded layers of polymethylmetacrylate (PMMA) that are either micromachined or structured by powder blasting. Two s...