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Application Of Inventory Electromagnetic Simulation In Intelligent Medical
Jan 25, 2019

There are many technological advances in the medical field that deserve our gratitude. Anesthesia allows patients in surgery to no longer need to "cuff the teeth." After the birth of antibiotics, doctors can cure the infection without bleeding. After entering the modern era, radio-frequency identification (RFID) systems have opened a window for a wide variety of healthcare innovations. However, in order to ensure stable system performance and good compatibility with other medical systems, any emerging medical technology must undergo rigorous testing, and radio frequency identification equipment in the biomedical field is no exception.

RFID system improves medical care

Radio frequency identification technology is widely used in many industries. However, when it comes to the medical field, size has become a key design challenge. The narrower end of the RFID tag is equivalent to one grain of rice, but this is not enough, and cell-level applications (such as research and diagnostics) need to be further reduced in size.

A team of researchers at Stanford University 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 works in conjunction with a dedicated RF identification reader to interpret data and monitor cell activity in real time. In the future, micro-RFID tags can also be connected to sensors to facilitate the development of advanced biotherapeutic technologies such as antibody detection and cancer cell destruction.

The surgeon implants the RFID microchip into the hands of the doctor. Soon, these tags can be implanted into single cells. Image courtesy of Paul Hughes. Licensed by CC BY-SA 4.0, shared through Wikimedia Commons.

Regardless of how thoughtful the doctor's clinical care is, it is difficult for patients to enjoy the puncture to detect vital signs. At Cornell University in the United States, researchers designed ultrahigh frequency (UHF) RFID tags that not only monitor vital signs such as heart rate, respiration, and blood pressure, or even touch patients at all. The label can be placed in a medical wristband or sewn into the garment. The RFID reader communicates wirelessly with the tag to simultaneously monitor multiple patients. 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 life system, medical personnel can save time and energy when measuring vital signs, patients become more comfortable, it is a multi-pronged.

Application of inventory electromagnetic simulation in intelligent medical

“Smart Fabric” is a potential application area for RFID systems. Image courtesy of Joshua Dickens. Licensed CC BY-SA 2.0, shared via Wikimedia Commons.

For example, sleep disorders and sleep apnea are often not effectively treated. Although they can lead to a variety of health and safety issues, few patients are accustomed to receiving nighttime sleep tests. After all, sleep monitoring is not only very expensive, but also easily disrupts the patient's schedule, and tests that are performed at home are difficult to operate. (I often do sleep tests at home. Every time I have to tie the system to my chest, stick the breathing tube to my face, and try my best to keep the monitor on my finger from falling off. The experience is extremely uncomfortable and inconvenient).

To support, researchers at RADIO6ENSE, Palermo and Rome have developed a passive RFID system that can remotely track sleep patterns in real time. This user-friendly passive RFID system has an RFID tag sewn into the pajamas that can operate at low power levels without the need for a battery, so the sleep mode data collector is not only accurate but also a safe Wearable device.

Electromagnetic interference and electromagnetic compatibility in biomedical RF identification design

Electromagnetic interference (EMI) and electromagnetic compatibility (EMC) are common phenomena in electromagnetic applications and can be analyzed by electromagnetic interference/compatibility testing.

Application of inventory electromagnetic simulation in intelligent medical

The anechoic chamber is one of the devices 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 extra mutual inductance that can occur between devices, with devastating effects on performance, operation, and reliability. A study published in 2011 showed that the National Center for Biotechnology Information, where contact with water, metals, or other equipment (contact is reasonable in medical settings) may affect the operation of the RFID system—or reverse devastating effects. In addition, in 2017, the US Food and Drug Administration issued an RFID report warning that electromagnetic interference can become a potential hazard when RFID systems interact with other medical devices.

Medical professionals are reluctant to hear "potential harm" as long as they involve the well-being and safety of patients. Simulation can help them at this time.

Optimize RF identification component design in COMSOL Multiphysics®

When designing RFID tags for biomedical applications, engineers must consider the performance of tags and readers, and the impact of RF tags on other medical devices 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 the design of RFID systems.

Optimize the detection and read range of UHF devices

UHF tags are easy to detect, whether they are close to the reader or far away, so UHF passive RFID tags are more popular and have a wider range of applications than low and high frequencies. For a wide range. UHF tags can also transfer data quickly, with better cost benefits.

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 values, we can predict the ideal label position on the patient and track the ideal position of the RFID reader for multiple patients at the same time.

Application of inventory electromagnetic simulation in intelligent medical

Application of inventory electromagnetic simulation in intelligent medical

Analysis of the electric field (top) and far-field radiation pattern (bottom) of the UHF RFID tag 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 in each direction on the label plane is essentially the same. The simulation results show that the performance of the RFID tag design is optimized, and the reading range extends a long distance.

Ensuring the safety of biomedical RFID systems

Now we build a basic RFID system model, which consists mainly of two parts:

Reader with large RF antenna

Answer tag with printed circuit board antenna

Application of inventory electromagnetic simulation in intelligent medical

Application of inventory electromagnetic simulation in intelligent medical

The geometry of the reader (top) and RFID tag (bottom).

The system works as follows: After the reader generates an electromagnetic field, it stimulates the chip inside the RFID tag. The tag's circuitry changes the electromagnetic field and the RFID reader's antenna recovers the changed signal.

With the addition of the “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 generated by one antenna in the system intercepting the current of the other antenna.

The simulation results in the figure below show the flux line and flux strength between the RFID tag and the reader. Based on the above results, we can calculate the mutual inductance of the system.

Application of inventory electromagnetic simulation in intelligent medical

The magnetic flux density of the RFID system.

By calculating the mutual inductance of the RFID system, one can predict the electromagnetic interference between the system and other medical devices. More importantly, the successful acquisition of a secure RFID tag design improves the patient's treatment level in a variety of ways.