BackgroundFundamental researches

We have discovered that ultrasound irradiation generates electricity and magnetism in biological tissues and materials. We are commercializing a technology for sensing the electromagnetic signals induced by ultrasound (acoustically stimulated electromagnetic signals: ASEM signals).

When a force is applied to a material, causing it to deform, electricity can be generated. This phenomenon is known as the piezoelectric effect, and it has been found to be significant in crystals and some ceramics, widely used in piezoelectric elements such as mobile speakers and sonar. We have discovered that this piezoelectric effect also occurs in living biological tissues. When biological tissue is distorted by ultrasound (acoustic pressure), electricity is generated within the body due to the piezoelectric effect. We have succeeded in noninvasively detecting and imaging the biological piezoelectricity with a receiving antenna placed outside the body.

The piezoelectric effect is originally a property defined by inorganic single crystals. The characteristics of the piezoelectric effect are determined by the order and symmetry of the atomic arrangement within the crystal. Even within biological systems, the piezoelectric effect is determined by the orderliness of molecular arrangements (crystallinity and orientation), such as collagen fiber structures. This means that measuring biological piezoelectricity allows for the pathohistological evaluation of characteristics such as fiber orientation and collagen accumulation.

Ultrasound imaging systems are in increasing demand as they contribute to the quality of healthcare and patients quality of life (QOL) by enabling rapid examinations in bedside settings at an outpatient examination room or at home. In addition to visual inspection and internal shape observation through echography, the introduction of the ASEM method as a ‘third eye’ for pathology evaluation would allow practitioners to make precise diagnoses and establish quicker treatment plans. Ultrasound imaging systems equipped with ASEM functionality are expected to offer possibilities beyond standard echography, including the assessment of the ‘quality’ of musculoskeletal organs (tendons, ligaments, bones, muscles, etc.) and the diagnosis of organ fibrosis in chronic diseases.

The Acoustically Stimulated ElectroMagnetic method (ASEM method) is based on the basic researches of IKUSHIMA Group at Tokyo University of Agriculture and Technology. For details, please visit IKUSHIMA Group's website.

ref.)
K. Ikushima, Progress Review, Jpn. J. Appl. Phys. 62, SJ0802 (2023)

Biomedical sensingMedical and healthcare

In fibrous biological tissues such as bones, tendons, ligaments, aortic walls, and aortic valves, ultrasound pressure produces electrical polarization (ASEM signal). Our technique visualises the crystallinity and orientation of collagen and elastin based on the size and orientation of this polarisation. In particular, we aim to assess the quality (crystallinity) of locomotory organs, to evaluate healing of fractures and tendon ruptures and to visualise/quantify the effects of exercise.

ref.)
Nature Research Highlights " The body electric: soft tissue makes electricity under stress"
APS Physics: Soft Biological Tissues Can Be Piezoelectric.
"Electric Polarization of Soft Biological Tissues Induced by Ultrasound Waves", Phys. Rev. Lett.123, 238101 (2019) (Original manuscript, Supplemental material)

Collagen, which makes up approximately 30% of the body's protein, plays a role in shaping our bodies, including the locomotor organs, internal organs and blood vessels. One of the main factors leading to the need for care and support is "disorders of the locomotor organs" such as fractures, falls and joint diseases. In the context of the global ageing population, maintaining one's own mobility of one's own volition is extremely important for independent living. In the working-age population, an early return to society after a fracture or tendon rupture has economic value for both the individual and society. This project aims to develop support for rehabilitation and everyday health management, as well as medical treatment, including diagnosis and treatment decisions. Through this project, we hope to realise a society in which each individual can maintain and manage his or her own health condition, enjoy appropriate exercise and lead a lively life.

Acoustomagnetic sensing and industrial inspectionIndustrial sensing

In magnetic materials such as steel, ultrasound pressure produces magnetic polarization (ASEM signal). The magnitude and direction of the polarization depend on the magnetic domain structure in the ultrasonic irradiated area.

The ASEM method allows magnetic imaging and local magnetic hysteresis measurements via ultrasonic scanning.

The acoustomagnetic sensing is used for nondestructive testing and evaluation of steel products and infrastructures.

ref.)
"Evaluation of Tensile Residual Stress in Welded Steel Plates Using Acoustically Stimulated Electromagnetic Response", IEEE T-UFFC 68, 1478 (2022)
"Magnetic hysteresis and magnetic flux patterns measured by acoustically stimulated electromagnetic response", Jpn. J. Appl. Phys. 54, 086601 (2015).
"Magnetic sensing via ultrasonic excitation" Rev. Sci. Instrum. 84, 044903 (2013)

HistoryASEM technology