Biology subjects

Iwasaka, M.

Publications and source records attributed to Iwasaka, M..

6 recordsLinked to original sources

bioRxiv2021

Modulation of optical speaker using biogenic guanine platelets floating in water

Microphones are miniature devices for sound detection. Various technologies have been developed to transfer sound properties onto other physical quantities, e.g., electricity. Over the past three decades, many studies have reported on optical sensing of sound. Most of these studies were performed via application of light interference at the edges of optical fibers. Several studies have reported on detection of sounds in the air or objects causing mechanical vibrations based on light interference. This work proposes an optical speaker which is a method to reconstruct and modulate sound from the power spectrum of light that has been reflected by guanine platelets floating in water droplet. The water droplet containing fish guanine platelets was placed on a piezoelectric membrane and acoustic vibration from the membrane propagated inside the droplet. A photomultiplier tube (PMT) then collected the light reflected from the water droplet. Without post-analysis of the measured light intensity, the analog output voltage from the PMT clearly sounded an audio speaker. In addition, it was found that the guanine platelets reflecting light operated as an audio equalizer.

biophysics↗

bioRxiv2021

On-chip light diffraction imaging of nano structures in the guanine platelet

Light projection over short distances can minimize the size of photonic devices, e.g., head-mounted displays and lens-free microscopes. Small lenses or light condensers without typical lenses are essential for light control in micron-scale spaces. In this work, micro-platelets floating in water are used for light projection near the image sensor. These platelets, which are made from guanine, have nanohole gratings and demonstrate light diffraction toward specific directions. By setting a thin water layer on the image sensors cover glass, each platelet in water forms column-or bar-code-shaped images on the screen. The projected image shapes and colors are inferred to contain information about nano-structures present in the guanine platelet. The proposed down-sized imaging technique can realize extremely compact and portable imagers for nanoscale object detection.

biophysics↗

bioRxiv2021

Real-time lens-free visualization of strong light scattering by biogenic guanine platelets

Microscopic observation system without lens has a potential to realize ubiquitous sensing network detecting micro/nano biological hazards to modern society because the lens-free imaging device can provide an extremely compact microscope. In addition to in slico micro-mirrors, liquid injectable organic micro-mirrors should be found and utilized for achieving the ideal imaging device for micro/nano objects. This study demonstrates a high contrast lens-free image of the projection from a biogenic guanine platelet floating in water. The fish guanine platelet generated intense and high directional diffraction as well as regular reflection of incident light. The light projection from guanine platelet individually formed an intense platelet-shaped image in real-time on CMOS image sensor arrays. A dynamic projection movie of the guanine platelet, the size of which was approximately 20 [~] 40 m x 5 [~] 10 m x 100 nm in thickness, was obtained in a small aqueous droplet whose height was less than 2 mm. The developed new lens-free technology using biogenic tiny platelet has an ability to portably visualize movements of the micro/nano objects interacting with the platelet. The compact lens-free inspection can contribute to keep our society in safe.

biophysics↗

bioRxiv2021

Optical and magnetic properties of particles containing guanine in strong basic solution

Guanine based particle is one of very efficient material to control light especially near the surface of animal body. Past studies reported that platelets of anhydrous guanin crystal are utilized by living creatures, and they can change their colour and light reflection intensity when the arrangement of platelets. Guanine has relatively high reflective index and its particle can exhibit a unique optical property. Under higher pH which can be provided by a high concentration of NaOH aqueous solution, guanine molecules formed a sodium salt particle which contain guanine. Here this work presents that particles containing guanine in basic aqueous solution with NaOH exhibited very strong shining and light reflection switching by magnetic fields. In addition, adding an extracted solution of a fish iridophore enhanced the formation of intensively light reflecting guanine particles floating in a strong basic solution.

bioengineering↗

bioRxiv2021

Rapid active-reflection display on dorsal stripes of Atherinomorus lacunosus

A large number of living creatures are able to use environmental light effectively as a biological display. The biological structural colors are very attractive not only within the coloring species but also to humans. However, the detailed function of bio-reflectors, which constitute the structural color with respect to communication, remains unknown. Atherinomorus lacunosus has alignments of iridophore spots on its dorsal part. Here it is found that a spot with a diameter of approximately 0.1 mm causes a rhythmic blinking of light owing to rapid reflection changes in iridophores existing inside the spot. The iridophores contain reflecting particles which show similar rotational responses to magnetic field under a light exposure. The speed of the intensity change of light at a frequency of approximately 1 Hz is proposed to be controlled by the nervous system of A. lacunosus. This kind of passive illumination may contribute to the development of a new optical device with low energy consumption.

bioengineering↗

bioRxiv2021

Dynamic blinking in the head of hardyhead silverside fish

Dynamic light reflection can serve a similar purpose to tools such as digital line processing devices. It is interesting, therefore, that evidence of dynamic light reflection can also be found in the animal kingdom and that there may be alternative ways of actuating light control. This study discovered that several features contained in the heads of hardyhead silverside fish, particularly around the edges of the iris, caused blinking using environmentally scattered light. Analyzing the blinking using recorded video of the fish iris revealed that circular cells existing in the iris changed their light intensity at 2 Hz. These 5-10-m-diameter cells are normally blue. However, it is found that a distinct light intensity changed in 0.04 seconds, and additional green and yellow colors overlapped with the blue. It is hoped that utilizing the mechanism that controls the rapid changes in light intensity using only environmental lighting can reduce electrical power usage in display devices.

biophysics↗