Akio Oki

Influences of electroosmotic flows in nanopillar chips on DNA separation: Experimental results and numerical simulations

The various potential factors affecting the performance of nanopillar chips on DNA separation were investigated from the viewpoints of both numerical calculations and actual experiments. To yield higher performance and replace the conventional DNA separation techniques such as microchip electrophoresis, the phenomenon specific to the nanopillar chips should be deeply understood. In this paper, although various factors affecting the performance of the nanopillar chips are considered, we focused on the effect of electroosmotic flow, which is particularly noticeable in quartz-made nanopillar chips. High-resolution separation of DNA was realized when an electroosmotic flow was suppressed by simply using a higher concentration of buffer, but DNA separation failed in the presence of an electroosmotic flow. It was confirmed from the numerical simulations and the direct observations that the deformation of DNA band during the injection process was induced by electroosmotic flow and consequently led to a poor resolution.

Battery-less wireless communication system through human body for in-vivo healthcare chip

This paper proposes a battery-less wireless communication system for in-vivo healthcare chip. We measured attenuation characteristics through a human body equivalent for six frequencies. Measured attenuation of 13.56 MHz is 47 dB through 15 cm thickness of human body equivalent. It is too difficult to use the usual modulations under such low power consumption. Then, we implemented the proposed system using the 13-56 MHz band with pulse interval modulation (PIM). In the simulated result, 16 mV of output voltage can be obtained at the outside receiver when coupling factor is 0.1. We also investigate antenna structure, and a tablet structure is suitable for the proposed system.

In Vivo Batteryless Wireless Communication System for Bio-MEMS Sensors

We propose a batteryless wireless communication system for in vivo healthcare chips. The system uses inductive coupling at 13.56 MHz with internal and external coils, and employs pulse interval modulation (PIM) to endure the large attenuation in the human body. A wireless communication circuit is presented in this paper, and 16 mV of output voltage can be obtained at the external receiver. The antenna coil structure is investigated, and it is found that a tablet structure is suitable for the proposed system.

RF attenuation characteristics for in vivo wireless healthcare chip

We investigate a wireless communication system for an in vivo healthcare chip. In this paper, we present measured attenuation characteristics through the human body at several frequencies. In the measurement, we use physiological saline and fresh meat instead of a real human body. From the measured results, we found that 13.56 MHz has an attenuation of 47 dB and is suitable for the proposed system.

Colorimetric microchip assay using our own whole blood collected by a painless needle for home medical care

We have developed a colorimetric measurement chip that measures triglycerides, total cholesterol, and high-density lipoprotein in 6 μL of whole blood collected with a painless needle. The chip can be used by patients to self-monitor certain health conditions at home. This chip contains a sharp 150 μm diameter stainless steel (SUS) needle that collects blood painlessly. The chip consists of three layers of injection-molded poly(methyl methacrylate) bonded together with two double-sided tapes. Two commercial reagents are used, and the volume ratio of plasma to reagent is doubled from the reagent specification to reduce the optical absorption length (and chip mass) by half. Centrifugal force separates the plasma from the blood, and then weighs out and mixes the plasma and reagents. A zigzag channel allows mixing of the plasma with the reagents mainly by vortex motion due to the centrifugal force generated at the corners of the channel. The measured values correlated well with conventionally tested values.

Near field communication chip using PIM for bio MEMS sensors

This paper presents a small-size wireless communication system for bio MEMS sensors, which uses the near field communication of 13.56MHz with Pulse Interval Modulation (PIM). In simulated result, 16mV of output voltage can be obtained at the outside receiver when coupling factor is 0.1.