Use of a simple arm-raising test with a portable laser Doppler blood flow meter to detect dehydration

Using micro electromechanical systems (MEMS) technologies, the authors have developed the world’s smallest, lightest, and least power-consuming laser Doppler blood flow meter. Unlike commercial fibre-type blood flow instruments, the new blood flow meter is invulnerable to any movements of the person wearing it and has a wireless transmitter. Utilizing the characteristics of the blood flow meter, the authors attempted to detect dehydration by having a subject simply raise an arm (arm-raising test) with the flow meter attached to a fingertip. Healthy young volunteers (20 men and two women, mean age 22.9, age range 21–27 years) were instructed to perspire in a sauna until they became dehydrated. The target dewatering ratio was 2 per cent, which was calculated from the body weight measured using a weight scale. Four markers were compared: mean blood flow (MBF) before arm-raising, MBF during arm-raising, maximum amplitude (MA) of the pulse wave during arm-raising, and inclination of reflex (IR) wave calculated from the recorded blood flow data for the non-dehydrated (before sauna) and dehydrated (3 h after sauna) states in the arm-raising test. Each of the mean total markers (MBF during arm-raising, MA, and IR) was significantly lower ( P < 0.05) during the dehydrated state than the non-dehydrated. These results suggest that three markers could detect dehydration and the blood flow meter devised has the potential to be used as a portable device for detecting dehydration.

Monolithic-integrated microlaser encoder

We have developed an extremely small integrated microencoder whose sides are less than 1 mm long. It is 1/100 the size of conventional encoders. This microencoder consists of a laser diode, monolithic photodiodes, and fluorinated polyimide waveguides with total internal reflection mirrors. The instrument can measure the relative displacement between a grating scale and the encoder with a resolution of the order of 0.01 microm; it can also determine the direction in which the scale is moving. By using the two beams that were emitted from the two etched mirrors of the laser diode, by monolithic integration of the waveguide and photodiodes, and by fabrication of a step at the edge of the waveguide, we were able to eliminate conventional bulky optical components such as the beam splitter, the quarter-wavelength plate, bulky mirrors, and bulky photodetectors.

Monolithically integrated optical displacement sensor based on triangulation and optical beam deflection

A monolithically integrated optical displacement sensor based on triangulation and optical beam deflection is reported. This sensor is simple and consists of only a laser diode, a polyimide waveguide, and a split detector (a pair of photodiodes) upon a GaAs substrate. The resultant prototype device is extremely small (750 microm x 800 microm). Experiments have shown that this sensor can measure the displacement of a mirror with resolution of better than 4 nm. Additionally, we have experimentally demonstrated both axial and lateral displacement measurements when we used a cylindrical micromirror (diameter, 125 microm) as a movable external object.

Optical trapping of low-refractive-index microfabricated objects using radiation pressure exerted on their inner walls

Optical trapping of transparent ring-shaped micrometer-sized objects with a refractive index lower than that of the surrounding medium has been demonstrated by use of a strongly focused TEM(00)-mode laser beam. Axial trapping of these objects is a result of the upward radiation pressure induced when the incident light strikes the inner wall and transmitted light leaves from the bottom. Transverse trapping of these objects occurs because the total repulsive radiation pressure exerted on the inner wall of the object is directed toward the laser beam axis. Three-dimensional manipulation of f luorinated polyimide micro-objects (refractive index n(1)= 1.525, outer diameter 10 microm, inner diameter 5 microm, and thickness 5.7 microm) in a high-refractive-index liquid (n(2)= 1.605) was experimentally shown to be possible by use of an objective lens with a wide range of numerical apertures from 1.25 to 0.5.