Eur. Phys. J. Appl. Phys.
Volume 90, Number 2, May 2020
International Symposium on Electromagnetic Fields in Mechatronics, Electrical and Electronic Engineering (ISEF 2019)
Article Number 20903
Number of page(s) 6
Section Physics of Energy Transfer, Conversion and Storage
Published online 30 June 2020

© EDP Sciences, 2020

1 Introduction

The influence of electromagnetic waves of low frequencies on organisms is not well known. It has been noticed that seismic electrical signals and low frequency disturbances can be detected by living organisms by the mechanism of forced ion oscillation under the action of external electromagnetic fields (EMF) on cells. Whereby electromagnetic fields can excite ion channels on cell membrane and affect the electrochemical state of the cell [1]. There are research and speculations about the positive and negative effects of using electromagnetic waves on living organisms. The relevant legal provisions regulating the maximum permissible levels of fields in the environment inhabited by humans have been introduced [2]. There are many ways in which magnetic fields interact with biological structures that cause changes in that structures. The question of whether these changes are safe for human health is still open [3]. However, apart from the negative impact, the beneficial effects of fields on the human body began to be noticed. Low frequency electromagnetic fields with a properly shaped spectrum and correctly applied have therapeutic properties [4,5]. In the recent research, external magnetic fields are used to interact with biological structures in which they activate ion channels for the flow of ions through the cell membranes [6]. Physical mechanisms of using magnetic fields that cause positive biological effects, in particular magnetic resonance therapy (TMR), have been presented in the article [7]. Magnetic fields are recently used as control stimuli in the area of neuroscience. Magnetic nanomaterials in biological structures can act as transducers processing stimuli from external magnetic fields into form perceived by neurons [8]. Studies provide strong evidence for the therapeutic effect of electromagnetic fields (EMFs) on different tissues. Biological effects on cells appear when the frequency of external magnetic field is adjusted to the cyclotron resonance frequency of ions and depend on the relationship between the magnitude of magnetic field and its frequency. Research show that the interaction is maximum when the frequency of the alternating field is equal to the frequency of the cyclotron resonance of the particular ion or some of its harmonics or sub-harmonics [9]. Magnetic fields with ultralow frequency and low amplitude have anti-cancer properties. The best therapeutic effect was stated for frequencies 1, 4.4, 16.5 Hz and intensity from 100 to 300 nT, in combination with static magnetic field of 42 μT. This inhibited the growth of the carcinoma in mice. In animals without tumors, exposed to the same magnetic fields, no pathological deviations from the norm was observed [10]. Electromagnetic field is often used to treat bone diseases, especially osteoporosis. The review of different types of the EMF with the common therapy parameters (intensity and frequency) used in bone treatment is presented in the article [11].

2 Influence of electromagnetic fields on biological systems

Magnetic fields act on living organisms through [3,57]:

  • fields of ionic currents generated by the electrodynamic interaction;

  • creation of a magnetomechanical force causing the movement of particles and atoms with uncompensated spins;

  • ionic cyclotron resonance.

As a result of the electrodynamic effect of the magnetic field on the biological system in the shape similar to the cylinder, an electric field of intensity E is generated, depending on the rate of change of induction B, expressed by the equation (1) (1)where: r is the radius of the cylinder.

The resultant field E produces inductive ion currents with the current density J according to the equation (2) (2)where σ is the conductivity of the biological system.

The magnetomechanical interaction on the biological system is based on the generation of a magnetomechanical force F causing motion of particles and atoms with uncompensated spins. The force F is induced by the magnetic field induction gradient B and is expressed by the equation (3) (3)where:

  • V is the volume of uncompensated spins;

  • µ: relative magnetic permeability of the biological system;

  • µ0: magnetic permeability of the vacuum;

  • ∇: vector differential operator Del, represented by the nabla symbol.

One of the phenomena occurring in body fluids of living organisms is ionic cyclotron resonance, whose fc frequency for ions of various elements in living organisms depends on the induction of a variable magnetic field. This frequency is expressed by the equation (4). The magnetic field stimulates ions only when the frequency of the magnetic field is equal to the frequency of the circular motion of the ion. Resonant frequencies for individual element ions depending on the magnetic field induction are presented in Table 1.

The movement of ions, in particular protons, in the internal electrolytic fluids through the walls of the vessels and the surrounding cell membranes depends on the energy supplied. This energy must be greater than the internal thermal energy, and should fit within the range of characteristic values of amplitude and frequency for biological cell. The impact of the described physical phenomena on biological structures consists in facilitating the exchange of specific ions with the biological cell outer environment [5].(4)where:

  • fc: frequency of the magnetic field in Hz;

  • B: average value of stream density along the axis in Tesla;

  • q: electric charge of ion.

For this phenomenon to occur, the cell must be supplied with specific energy higher than thermal energy. The magnetic field induction value must be within the characteristic range for the biological cell.

The impact of the described physical phenomena on biological structures consists in facilitating the exchange of specific ions with the environment. In the cell membranes of most animal cells there are so-called ion pumps, which are physiological complexes of specialized proteins. They participate in the active transport, through cell membranes, of specific ions, even against the gradient of their concentrations. We distinguish ion pumps associated with certain elements important from the point of view of living organisms:

  • sodium and potassium;

  • calcium.

The sodium-potassium pump is responsible for maintaining a certain gradient of Na+–K+ ion concentration. It removes sodium ions from the inside of the cell and introduces potassium ions into the cell. It also takes an active part in the transport of sugars and amino acids to the organic cell. The volume of the cell is regulated and the stimulation of the nerve and muscle cells is controlled. This affects the restoration and maintenance of the ion balance. The calcium pump is involved in the active transport of Ca2+ ions from the cytoplasm outside or into another cellular compartment. In this way, the level of calcium ions is maintained optimal for the functioning of the cell's biochemical systems and at the same time preventing the accumulation of excess Ca2+ [12,13]. The distribution of concentrations of individual element ions is shown in Figure 1.

On the cellular membranes, in the stabilized conditions, there is the so-called resting potential of the membrane. This potential is stabilized when the ion flow is balanced and there is no further accumulation of charge differences across the membrane. The measure of the membrane potential is the voltage existing across the membrane. The resting membrane potential of organic cells ranges from −20 mV to −200 mV.

The effect of the interaction of magnetic fields is the change in the permeability of biological membranes [14]. Many structures of the human body are made of liquid crystals. These include spinal cord, ovaries, sex hormones, DNA, internal layers of biological membranes. The action of the magnetic field causes many structural changes which results in a change in the membrane permeability, causing a series of reactions in the tissues. This causes a change in the penetration of Ca2+, K+, Na+ between the cell and the environment [13,15].

Table 1

Resonant frequencies for individual element ions depending on the magnetic field induction [5].

thumbnail Fig. 1

Ion concentration inside and outside the cell [12].

3 Application of the low frequency magnetic field in medicine

A very important feature of the low frequency magnetic field, from the point of view of medicine is the ability to penetrate all cells of the human body. The cells, tissues, substances or ions found in the body react in different ways to the external magnetic field, causing changes in their structures. All substances from which organic structures are built, including the human body can be divided into:

  • diamagnetics weakening the action of the magnetic field;

  • paramagnetics enhancing the magnetic field in a small extent;

  • ferromagnetics that greatly enhance the effect of the external magnetic field.

An example of diamagnets is oxyhemoglobin or vitamins (with the exception of B12 vitamin); paramagnets are hematin, myoglobin or enzymes; ferromagnetic are compounds that are components of the human body, e.g. iron that is part of hemoglobin. Placing the body in the area of the magnetic field causes its influence on the mentioned substances [14].

The pulsating magnetic field causes many changes at the cellular level. These changes have a beneficial effect on tissues, acting therapeutically and accelerating treatment processes. The most frequently mentioned effects of the magnetic field include:

  • analgesic effect;

  • calming effect;

  • anti-inflammatory effect;

  • anti-swelling effect;

  • increase in blood flow in the blood vessels;

  • acceleration of regeneration and healing processes.

Magnetic fields acting on tissues stimulate bone growth [14]. The variable magnetic field induces electric currents in the tissues. It activates piezoelectric systems, examples of which are collagen, dentine, keratin and other proteins. Due to the load on one bone surface, the charges on the opposite surface are polarized. In this way, a piezoelectric current is created that stimulates the bone growth.

4 Signals used in magnetic field therapy

To bring the effective interaction of low frequency fields with the human body fields with appropriate intensity and frequency should be generated. The therapy with a magnetic field can be divided into two main types:

  • magnetotherapy;

  • magnetostimulation.

Magnetic field applicators with coils of various inductions and shapes are used in therapies. Usually they are used in the form of pillows, mats, Helmholtz coils and point applicators. Magnetotherapy is performed using low frequency magnetic fields in the range from 5 Hz to 40 Hz. The intensity of magnetic field induction generated by the applicators during the magnetotherapy is up to several mT. In this type of magnetic therapy signals of sinusoidal, triangular and rectangular shapes are used, as shown in Figure 2.

Magnetostimulation uses signals with specific characteristics that are usually protected by patents owned by manufacturers. Exemplary signals used in magnetostimulation are presented in Figure 3. In this therapy, applicators generating the induction up to 100 µT, are usually used. The magnitude of magnetic field induction is comparable to the induction of the Earth's magnetic field. The frequency spectrum reaches several kHz.

The intensity of the therapy signals is set in the range of 12 levels with a step of one. The level of 12 corresponds to 1.8 A current flowing through the applicator. The duration of magnetostimulation and magnetotherapy processes depends on the program selected at the device. For magnetostimulation the treatment times are 8, 10 or 12 min. For magnetotherapy treatment time is set in the range of 10 min to 30 min with increments of 5 min.

thumbnail Fig. 2

Examples of signals used in magnetotherapy.

thumbnail Fig. 3

Examples of signals used in magnetostimulation.

5 Device for magnetic field therapy

For the transport of ions, appropriate current signal should be generated and converted by an applicator into magnetic field which is then applied to a human body. The main idea of the system for activating the transport of ions in biological structures with the use of magnetic field is shown in Figure 4.

The system consists of the following modules:

  • control and visualization module which controls and monitors all parts of the system;

  • sample memory in which patterns of control currents are stored;

  • digital to analog converter which changes the values of digital samples to analog voltages;

  • voltage to current converter which amplifies current signals and controls the applicators;

  • magnetic field applicators with different sizes and shapes which are chosen accordingly to the treatment;

  • power supply module.

For the purpose of activating of ions transport in biological structures a specialized control unit was developed, equipped with modules for powering, monitoring and controlling the operation of magnetic field generation. The control unit consists of three main functional blocks: external power supply unit, touch panel and control module. The block diagram (Fig. 5) shows the control unit for activating ion transport. The control unit uses a LCD display with LVDS interface and touch keyboard. The display is controlled by the SoM (System on Module). The SoM module collects, stores and processes information from individual systems and manages their work. It also enables data exchange with the processor of the executive module with the use of internal UART serial transmission bus. The SoM module works with a clock frequency of 24 MHz. Depending on the system needs the built-in PLL circuit multiplies this frequency to frequency in 400 MHz to 1 GHz range. In the control module the basic power supply is 5V. All voltages necessary for operation of the SoM module and the display are generated from this voltage. In this module it is possible to play audio messages saved in appropriate files. The controller has built-in data access channels via Bluetooth and WiFi ports. The WiFi module is a fully integrated single module compatible with the 802.11 b/g/n standard in the 2.4 GHz band, designed for portable and battery-powered applications. It is a simple solution for devices that support the operating system and the TCP/IP stack. The Bluetooth Smart Ready HCI module is designed for applications where both Bluetooth classic and Bluetooth low energy are required. The module operates in the 2.4 GHz frequency band.

The SoM module works under the control of the Linux operating system. This system contains a number of libraries to support the SoM hardware resources. The main purpose of the SoM module is the implementation of the user interface with the use of LCD display and keyboard. The module also enables the implementation of a remote interface, using the TCP/IP protocol, allowing control and monitoring of the device in the same way as with the use of the local interface. The easiest way to implement such interfaces is currently the use of web technology. The user interface of the device for activating ion transport has been implemented in the form of a web server running on the Linux system. Due to the large and often changed content of the graphical interface, the website was designed as a Single Page Application (SPA). Websites using the SPA are characterized by a fast response rate to events because full page content is sent only once when it is first loaded into the browser. During further operations, only fragments that need refreshing are loaded. The use of the web technology in the implementation of the user interface allows monitoring and control of the therapy with any device equipped with a web browser, e.g. laptop, tablet, smartphone. This also applies to the local interface in the SoM module, which was implemented as a web browser application called from the Linux system. The data presented in the user interface are stored in the local database of the SoM module. This database is filled with data derived from the user's interaction with the device and data from the executive device acquired via the UART serial port. The transmitted data blocks are secured using CRC checksums and encryption.

The STM32F103 microcontroller with 512 kB Flash and 64 kB RAM memory was used to process the therapeutic signals and manage the treatment cycle. Signal samples are stored in the processor's internal memory. The graphic presentation of the memory area containing the sampled therapeutic signals is shown in Figure 6. These signals are used to control internal D/A converter of the microprocessor. The samples are transferred from the memory to the 12-bit D/A converter via the built-in direct memory access (DMA) channel. The applied method of signal generation minimizes the processor's CPU load. Voltage signals from D/A converter are converted to the current signals which directly drives magnetic field applicators. In the control unit the following types of diagnostics are implemented:

  • diagnostics of the applicator type;

  • diagnostics of the applicator's coil continuity.

The control unit is adapted to work with an external 230 V/50/60 Hz power supply with a 24 VDC output voltage. The device has a built-in rechargeable battery, enabling its uninterrupted operation during a power failure, or in conditions when there is no mains voltage.

The control unit task is to perform the following functions:

  • generation of signals of the desired shape and amplitude;

  • management of polarization of therapeutic signals;

  • self-monitoring of device circuits;

  • automatic control of applicator types and monitoring of their state;

  • grouping of appropriate signals to achieve a therapeutic effect;

  • signaling of the device operation status by means of acoustic and optical signaling (e.g. the duration of therapy);

  • preview of the time left till the end of the treatment;

  • automatic switching off of the equipment after the procedure or in the event of an abnormal operation of any of its circuits.

thumbnail Fig. 4

Functional blocks of the system for activating the transport of ions in biological structures [16].

thumbnail Fig. 5

Block diagram of the control unit for magnetic field therapy.

thumbnail Fig. 6

Graphical presentation of therapeutic signal samples stored in the memory of the microcontroller [16].

6 Summary

The described medical electronic system is used for activating the ions transport in biological structures in therapeutic applications including diseases of the musculoskeletal system, neurological system, cardiovascular diseases, skin diseases, osteoporosis treatment and in dentistry. In each of these areas there is a positive effect of magnetic field therapy on the patients' health condition [13,14,17,18]. The presented device has a flexible hardware and software construction enabling the creation of magnetic fields of any shape, frequency and amplitude. The controller has an open architecture and can be operated locally or through a remote management system. The control unit works with many magnetic field applicators with different resistance and inductance parameters. Built-in self-monitoring mechanisms allow for its safe operation both in clinics and at home. The discussed control unit passed all the required tests for a medical device and obtained the appropriate certificate.

Author contribution statement

The authors reviewed the literature in terms of applications of magnetic fields in medicine. They developed a model of the device for magnetic field therapy and conducted its research. The results of the work were presented in the article. J. Chudorliński and P. Prystupiuk elaborated hardware. L. Książek developed software. All authors wrote and edited the manuscript.


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Cite this article as: Jerzy Chudorliński, Leszek Książek, Piotr Prystupiuk, Electronic system for activating ions in biological structures, Eur. Phys. J. Appl. Phys. 90, 20903 (2020)

All Tables

Table 1

Resonant frequencies for individual element ions depending on the magnetic field induction [5].

All Figures

thumbnail Fig. 1

Ion concentration inside and outside the cell [12].

In the text
thumbnail Fig. 2

Examples of signals used in magnetotherapy.

In the text
thumbnail Fig. 3

Examples of signals used in magnetostimulation.

In the text
thumbnail Fig. 4

Functional blocks of the system for activating the transport of ions in biological structures [16].

In the text
thumbnail Fig. 5

Block diagram of the control unit for magnetic field therapy.

In the text
thumbnail Fig. 6

Graphical presentation of therapeutic signal samples stored in the memory of the microcontroller [16].

In the text

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