Momoko Kumemura

Integrated Broadband Microwave and Microfluidic Sensor Dedicated to Bioengineering

This paper presents an innovative high-frequency- based biosensor, which combines both microwave detection and microfluidic network for time-efficient and accurate biological analysis. It is composed of a coplanar waveguide with a microfluidic channel placed on top. With the help of an appropriate de-embedding technique and modeling of the measurements, the relative effective permittivity of human umbilical vein endothelial cells has been evaluated successfully. Furthermore, experiments have been performed with the sensor on various cell concentrations in suspension, which validates its use in bioengineering applications such as cell quantification and counting in solution. This sensor requires no direct contact or use of labels on the cells, contrary to other usual types of biosensors (optical, mechanical or dc/low-frequency-detection-based ones).

Silicon Nanotweezers With Subnanometer Resolution for the Micromanipulation of Biomolecules

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 on silicon-on-insulator technology and combines KOH wet anisotropic etching and deep reactive ion etching of silicon to form sharp nanotips and high aspect ratio microstructures, respectively. In the designed prototype, the initial gap between the tips was around 20 mum. The device showed a maximum displacement of about 2.5 mum, and we could achieve a resolution better than 0.2 nm (in static mode). We measured a resonant frequency of 2.5 kHz and a quality factor (Q factor) of 50 in air. The instrument was used to perform static and dynamic mechanical manipulations on DNA molecules, and we could distinctly observe the viscoelastic behavior of DNA bundles from these experiments.

Resonant based microwave biosensor for biological cells discrimination

This publication deals with a resonant RF-based biosensor for in-liquid operation. Stop-band filter modeling and characterizations are investigated in order to discriminate dead and alive suspensions of human cultured cells. This proof of concept demonstrator features noticeable contrasts on both resonant frequency (7%) and amplitude (2.1 dB). Theses results consequently demonstrate that RF detection can provide a non invasive sensing technique, which is compatible with a lab-on-a-chip approach to discriminate the pathological state of cells.

New broadband and contact less RF / microfluidic sensor dedicated to bioengineering

This paper presents an innovative RF based biosensor, which allies both RF/microwave detection and a microfluidic network for quick and precise biological analysis. It is composed of a coplanar waveguide with a microfluidic channel placed on top. Thanks to an appropriate de-embedding technique and modeling of the measurements, the relative effective permittivity of HUVEC human cells has been evaluated successfully. Furthermore, the sensor has been experimented for various cells concentrations in suspension, which validates its use for bioengineering and especially cells quantification and counting in solution, without any direct contact or use of labels on the cells, in the contrary to other usual biosensors types (optical, mechanical or DC/low frequency detection based ones).

Silicon Nanotweezers with Adjustable and Controllable Gap for the Manipulation and Characterization of DNA Molecules

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 microelectromechanical system (MEMS) consists of a pair of opposing tips, the distance of which can be accurately adjusted thanks to a high resolution differential capacitive sensor. The device shows a resolution of 5 nm for a displacement range of 3 mum (static mode). It has a resonant frequency at 2 kHz and a quality factor of 40 in air, and 550 in vacuum

Towards single biomolecule handling and characterization by MEMS

AbstractApplications of microelectromechanical systems (MEMS) technology are widespread in both industrial and research fields providing miniaturized smart tools. In this review, we focus on MEMS applications aiming at manipulations and characterization of biomaterials at the single molecule level. Four topics are discussed in detail to show the advantages and impact of MEMS tools for biomolecular manipulations. They include the microthermodevice for rapid temperature alternation in real-time microscopic observation, a microchannel with microelectrodes for isolating and immobilizing a DNA molecule, and microtweezers to manipulate a bundle of DNA molecules directly for analyzing its conductivity. The feasibilities of each device have been shown by conducting specific biological experiments. Therefore, the development of MEMS devices for single molecule analysis holds promise to overcome the disadvantages of the conventional technique for biological experiments and acts as a powerful strategy in molecular biology. FigureTowards single bio molecular handling and characterization by MEMS

Improvement of Silicon Nanotweezers Sensitivity for Mechanical Characterization of Biomolecules Using Closed-Loop Control

In this paper, we show that closed-loop control can be advantageously used for the characterization of mechanical properties of biomolecules using silicon nanotweezers (SNT). SNT have already been used in open-loop mode for the characterization of mechanical properties of DNA molecules. Up to now, such an approach allows the detection of stiffness variations equivalent to about 15 DNA molecules. Here, it is shown that this resolution is inversely proportional to the resonance frequency of the whole system and that real-time feedback control with state observer can drastically improve the performances of the tweezers used as biosensors. Such improvement is experimentally validated in the case of the manipulation of fibronectin molecules. The results are promising for the accurate characterization of biopolymers such as DNA molecules.

Mechanical Characterization of Biomolecules in Liquid using Silicon Tweezers with Subnanonewton Resolution

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 micromanipulation and biomechanical characterization of DNA bundles in a liquid solution. By combining this instrument with a microscopic displacement measurement technique based on Fourier transform image processing, we could achieve a force resolution of 25 pN - a level which is within the single-molecule sensing range - and validate a novel approach for stress-strain measurements.

Real-time mechanical characterization of DNA degradation under therapeutic X-rays and its theoretical modeling

The killing of tumor cells by ionizing radiation beams in cancer radiotherapy is currently based on a rather empirical understanding of the basic mechanisms and effectiveness of DNA damage by radiation. By contrast, the mechanical behaviour of DNA encompassing sequence sensitivity and elastic transitions to plastic responses is much better understood. A novel approach is proposed here based on a micromechanical Silicon Nanotweezers device. This instrument allows the detailed biomechanical characterization of a DNA bundle exposed to an ionizing radiation beam delivered here by a therapeutic linear particle accelerator (LINAC). The micromechanical device endures the harsh environment of radiation beams and still retains molecular-level detection accuracy. In this study, the first real-time observation of DNA damage by ionizing radiation is demonstrated. The DNA bundle degradation is detected by the micromechanical device as a reduction of the bundle stiffness, and a theoretical model provides an interpretation of the results. These first real-time observations pave the way for both fundamental and clinical studies of DNA degradation mechanisms under ionizing radiation for improved tumor treatment.

A rapid and practical technique for real-time monitoring of biomolecular interactions using mechanical responses of macromolecules

Monitoring biological reactions using the mechanical response of macromolecules is an alternative approach to immunoassays for providing real-time information about the underlying molecular mechanisms. Although force spectroscopy techniques, e.g. AFM and optical tweezers, perform precise molecular measurements at the single molecule level, sophisticated operation prevent their intensive use for systematic biosensing. Exploiting the biomechanical assay concept, we used micro-electro mechanical systems (MEMS) to develop a rapid platform for monitoring bio/chemical interactions of bio macromolecules, e.g. DNA, using their mechanical properties. The MEMS device provided real-time monitoring of reaction dynamics without any surface or molecular modifications. A microfluidic device with a side opening was fabricated for the optimal performance of the MEMS device to operate at the air-liquid interface for performing bioassays in liquid while actuating/sensing in air. The minimal immersion of the MEMS device in the channel provided long-term measurement stability (>10 h). Importantly, the method allowed monitoring effects of multiple solutions on the same macromolecule bundle (demonstrated with DNA bundles) without compromising the reproducibility. We monitored two different types of effects on the mechanical responses of DNA bundles (stiffness and viscous losses) exposed to pH changes (2.1 to 4.8) and different Ag+ concentrations (1 μM to 0.1 M).