Inventory of the application of electromagnetic simulation in smart medicine
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There are many technological advances in the medical field that we are grateful for. Anesthesia eliminates the need for patients during surgery to “grind their teeth.” After antibiotics are born, doctors can cure infections without bleeding. After entering the modern era, radio-frequency identification (RFID) systems have opened a window for a variety of innovations in healthcare applications. However, in order to ensure stable system performance and good compatibility with other medical systems, any emerging medical technology must undergo rigorous inspections, and radio frequency identification equipment in the biomedical field is no exception.
RFID system improves the level of medical care
Radio frequency identification technology has wide applications in many industries. However, when it comes to the medical field, size has become a key design problem. The narrow end of the RFID tag is as large as a grain of rice, but this is not enough. Cell-level applications (such as research and diagnosis) need to further reduce the design size.
A team of researchers at Stanford University has developed a miniature RFID tag that can be implanted into cells (such as skin or cancer cells). The label is about one-fifth the thickness of a human hair. It is used in conjunction with a special radio frequency identification reader to interpret data and monitor cell activities in real time. In the future, micro RFID tags can also connect sensors to each other to promote the development of advanced biotherapeutic technologies, such as antibody detection and cancer cell destruction.
The surgeon implants the RFID microchip in the doctor’s hand. Soon, these tags can be implanted into single cells. Image courtesy of Paul Hughes. Licensed by CC BY-SA 4.0, shared via Wikimedia Commons.
No matter how thorough the doctor’s clinical care is, it may be difficult for patients to enjoy being pricked to detect their vital signs. At Cornell University in the United States, researchers designed ultrahigh frequency (UHF) RFID tags, which can not only monitor vital signs such as heart rate, respiration, and blood pressure, but do not even need to contact the patient at all. The label can be put into a medical wristband or sewn into clothes. RFID readers communicate with tags wirelessly, and can monitor multiple patients at the same time. The system relies on back-end software to manage, interpret and monitor data. As a result, doctors can accurately understand the characteristics of each patient’s vital system, medical staff can save time and energy when measuring vital signs, and patients become more comfortable.
“Smart fabric” is a potential application area of the RFID system. Image courtesy of Joshua Dickens. It has been licensed by CC BY-SA 2.0 and shared via Wikimedia Commons.
For example, sleep disorders and sleep apnea are often not treated effectively. Although they may cause a variety of health and safety issues, few patients are accustomed to receiving night sleep tests. After all, sleep monitoring is not only very expensive, but also easily disrupt the patient’s schedule, and tests that can be performed at home are difficult to operate. (I myself often perform sleep tests at home, every time I have to tie the system to my chest, stick the breathing tube on my face, and try my best to keep the monitor on my finger from falling off, the experience is extremely uncomfortable and inconvenient).
To provide support, researchers from the Italian company RADIO6ENSE, the University of Palermo, and the University of Rome have developed a passive RFID system that can track sleep patterns remotely and in real time. This user-friendly passive RFID system has an RFID tag sewn into the pajamas. It can operate at low power levels and does not require batteries at all. So this sleep mode data collector is not only accurate, but also a safe Wearable devices.
Electromagnetic Interference and Electromagnetic Compatibility in the Design of Biomedical Radio Frequency Identification
Electromagnetic interference (EMI) and electromagnetic compatibility (EMC) are common phenomena in electromagnetic applications, which can be analyzed through electromagnetic interference/compatibility testing.
The anechoic chamber is one of the equipment that can measure the electromagnetic interference/electromagnetic compatibility of the antenna.
When discussing RFID tags for biomedical applications, electromagnetic interference has received special attention because of the excess mutual inductance that may occur between devices, which can have a destructive effect on performance, operation, and reliability. A study published in 2011 showed that the National Center for Biotechnology Information, contact with water, metal or other equipment (contact is reasonable in medical settings) may affect the operation of the RFID system-or have a reverse destructive effect. In addition, the U.S. Food and Drug Administration issued a report on RFID in 2017. They warned that electromagnetic interference would become a potential hazard when the RFID system interacts with other medical devices.
As long as the well-being and safety of patients are involved, medical professionals are never willing to hear such statements as “potential harm”. Simulation can help them at this time.
Optimize the design of radio frequency identification components in COMSOL Multiphysics®
When designing RFID tags for biomedical applications, engineers must consider the performance of tags and readers, as well as the impact of radio frequency identification on other medical equipment and systems. They can first characterize individual devices (such as RFID tags) to create a good starting point for electromagnetic interference analysis. Electromagnetic simulation can be used to calculate the mutual inductance in RFID system design.
Optimize the detection and reading range of UHF devices
UHF tags are easily detected regardless of the distance between the reader and the reader or far away. Therefore, compared with low frequency and high frequency, UHF passive RFID tags are more popular and have a wider range of applications. For extensive. UHF tags can also transmit data quickly and have better cost benefits.
In order to calculate the detection and reading range of UHF RFID tags, you can use the “RF Module” attached to the COMSOL Multiphysics® software. RF simulation can calculate the default electric field mode or electric field of the label design. Based on the calculated value, we can predict the ideal tag position on the patient and the ideal position of the RFID reader to track multiple patients at the same time.
Analyzing the electric field (top) and far-field radiation pattern (bottom) of UHF RFID tags can enhance the detection capability of the device and expand the measurement range.
Simulation analysis can also generate far-field radiation patterns for tags. For example, the upper model shows that the radiation pattern of each direction on the label plane is basically the same. The simulation results show that the performance of the RFID tag design has been optimized, and the reading range has been extended a long distance.
Ensuring the safety of biomedical RFID systems
Now we build a basic RFID system model, which is mainly composed of two parts:
Reader with large radio frequency antenna
Answering label with printed circuit board antenna
The geometry of the reader (top) and RFID tag (bottom).
The working principle of the system is as follows: After the reader generates an electromagnetic field, it stimulates the chip in the RFID tag. The circuit of the tag will change the electromagnetic field, and then the antenna of the RFID reader will restore the changed signal.
With the additional “AC/DC module” and magnetic field interface of COMSOL Multiphysics, designers can simulate the inductive coupling between the reader and the tag. The mutual inductance can be calculated by detecting the total magnetic flux produced by one antenna intercepting the current of the other antenna in the system.
The simulation result in the figure below shows the magnetic flux lines and magnetic flux intensity between the RFID tag and the reader. Based on the above results, we can calculate the mutual inductance of the system.
The magnetic flux density of the RFID system.
By calculating the mutual inductance of the RFID system, people can predict the electromagnetic interference between the system and other medical equipment. More importantly, it succeeded in obtaining a secure RFID tag design to improve the treatment level of patients in various ways.
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