Sadato Hongo

Single-Nanoparticle Detection Using a Low-Aspect-Ratio Pore

We explored single-particle translocation through a low thickness-to-diameter aspect ratio Si(3)N(4) pore mimicking graphene nanopore structure by a resistive pulse method. Ionic conductance of 0.05 aspect ratio pores scales linearly with the diameter, indicating predominant contribution of the access resistance to the ion transport. We find that the access resistance changes little during particle translocation. Furthermore, we observe enhanced particle capture rates via the strong electric field extended outside the low-aspect-ratio pore mouth. We also demonstrate electrical discrimination of two different sized particles using the low-aspect-ratio pore sensor with the constant access resistance assumption. The present findings indicate the potential utility of nucleotide-sized graphene nanopores as an electrical sensing platform for single-base identification via transmembrane ionic current blockade detections.

A 40-GHz D-type flip-flop using AlGaAs/GaAs HBT's

We report master-slave D-type flip-flop (D-FF) circuit implemented with AlGaAs/GaAs HBTs. The fabricated HBTs had an f/sub T/ of 107 GHz and an f/sub max/ of 110 GHz. To maximize the speed, the logic swing and transistor size in the IC were optimized. In the D-FF, to facilitate the high-speed testing, a selector circuit was integrated on the same chip. As a result, the operation of this IC was confirmed up to 40 GHz, which is the highest speed in D-FF. >

Particle Trajectory-Dependent Ionic Current Blockade in Low-Aspect-Ratio Pores

Resistive pulse sensing with nanopores having a low thickness-to-diameter aspect-ratio structure is expected to enable high-spatial-resolution analysis of nanoscale objects in a liquid. Here we investigated the sensing capability of low-aspect-ratio pore sensors by monitoring the ionic current blockades during translocation of polymeric nanobeads. We detected numerous small current spikes due to partial occlusion of the pore orifice by particles diffusing therein reflecting the expansive electrical sensing zone of the low-aspect-ratio pores. We also found wide variations in the ion current line-shapes in the particle capture stage suggesting random incident angle of the particles drawn into the pore. In sharp contrast, the ionic profiles were highly reproducible in the post-translocation regime by virtue of the spatial confinement in the pore that effectively constricts the stochastic capture dynamics into a well-defined ballistic motion. These results, together with multiphysics simulations, indicate that the resistive pulse height is highly dependent on the nanoscopic single-particle trajectories involved in ultrathin pore sensors. The present finding indicates the importance of regulating the translocation pathways of analytes in low-aspect-ratio pores for improving the discriminability toward single-bioparticle tomography in liquid.

Trapping and identifying single-nanoparticles using a low-aspect-ratio nanopore

Manipulation of particles and molecules in fluid is a fundamental technology in biosensors. Here, we report electrical trapping and identification of single-nanoparticles using a low-aspect-ratio nanopore. Particle trapping and detrapping are implemented through a control of the cross-membrane electrophoretic voltage. This electrical method is found to enable placing an individual nanoparticle in vicinity of a lithographically-defined nanopore by virtue of the balance between the two counteracting factors, electrostatic and electroosmotic forces. We also demonstrate identification of trapped nanoparticles by the ionic current through the particle-pore gap space. This technique may find applications in electrode-embedded nanopore sensors.

CMOS Integrated DNA Chip for Quantitative DNA Analysis

Quantitative gene expression analysis, based on an electrochemical DNA-detection method uses immobilized DNA probes on Au electrodes with diameters from 200mum to 2mum. Cyclic voltammetry is used to measure anodic current from the intercalators. The 25times3mm2 IC, fabricated in 1mum 2M CMOS, contains 40 electrodes, 1600 transistors and dissipates 150mW at plusmn3.3V

DC to 40-GHz broad-band amplifiers using AlGaAs/GaAs HBT's

In this paper, we report two types of broad-band amplifiers implemented with AlGaAs/GaAs HBTs. One is a Darlington feedback amplifier and the other is a transimpedance amplifier. In the former circuit, a dc gain of 9.5 dB and a -3-dB bandwidth of 40 GHz were achieved. In the latter circuit, a transimpedance gain of 50 dB/spl Omega/ and a -3-dB bandwidth of 27 GHz were achieved. To our best knowledge, they are the highest speed in each circuit configuration. >

Highly reproducible fabrication technology for passivated AlGaAs/GaAs heterojunction bipolar transistors with Pt/Ti/Pt/Au base electrodes

A highly reproducible fabrication technology for passivated heterojunction bipolar transistors (HBTs) has been developed. A thermally stable Pt/Ti/Pt/Au base electrode metal penetrates through the Al 0.3 Ga 0.7 As emitter layer to contact the base layer. This feature leads to the formation of the base passivation layer. A citric-acid-based selective etchant eliminates the ambiguity of etching and thus confirms the reproducibility of passivation layer thickness. The excess base leakage current density was reduced to about 1 μA/μm