With the rapid advancements in artificial intelligence, IoT, and sensing technologies, bio-monitoring solutions are transitioning from traditional contact-based and intermittent measurements to more intelligent, continuous, and unobtrusive health monitoring models. From tracking vital signs in hospitals to smart homes, telemedicine, and public safety scenarios, bio-monitoring not only plays a critical role in improving medical efficiency and accuracy but also demonstrates immense value in preventive healthcare, chronic disease management, and early warning systems for sudden health events. This article introduces the applications and development of Ballistocardiography (BCG) and piezoelectric film sensing bio-monitoring solutions, as well as the related solutions offered by Murata.
Contactless physiological monitoring via detection of minute cardiac vibrations
BCG technology is a contactless physiological monitoring method that detects subtle mechanical vibrations caused by cardiac contractions and blood ejection to indirectly obtain cardiac activity information. It does not require electrode patches or wearable devices, enabling continuous vital sign tracking in comfortable environments. In recent years, it has been increasingly widely applied in contactless bio-monitoring.
Murata's BCG (Ballistocardiogram) sensor works by detecting the tiny vibrations and movements produced by the heartbeat and blood flow within the human body. Below is a simplified explanation of its working principle:
Sensing Minute Body Movements:
When the heart beats, it causes subtle movements and vibrations throughout the body. These movements are extremely small, often in the micrometer range.
Micro-Electro-Mechanical Systems (MEMS) Technology:
Murata’s BCG sensor uses MEMS technology, which involves tiny mechanical structures integrated with electronic circuits. These structures are highly sensitive to vibrations and motion.
Detection Mechanism:
The sensor detects the mechanical vibrations caused by the heartbeat by converting these physical movements into electrical signals.
Signal Processing:
The electrical signals are processed to extract meaningful information about heart rate, heart rhythm, and other cardiovascular parameters.
Non-Invasive Monitoring:
Because it senses body vibrations externally, the BCG sensor allows for non-contact or minimally obtrusive heart monitoring, suitable for applications like sleep monitoring, wearable devices, and healthcare.
In summary, Murata’s BCG sensor captures heart-induced body vibrations using sensitive MEMS components and converts them into electrical signals for health monitoring purposes.
BCG can be applied in hospital wards and intensive care units (ICUs), smart homes and sleep monitoring, elderly fall and health alerts, and remote health management. For example, in hospital wards and ICUs, it can continuously monitor heart rate, heartbeat interval variability (HRV), and stroke volume, reducing skin irritation and infection risks associated with contact sensors. When applied in smart homes and sleep monitoring, it can analyze heart rate, respiration, body movements, and sleep stages during sleep. It can be hidden in mattresses, pillows, or bed frames to achieve unobtrusive monitoring.
Additionally, in elderly fall and health alerts, BCG can monitor long-term changes in cardiac function, combined with abnormal pattern detection to prevent cardiac events, without requiring user cooperation, making it suitable for the elderly population. BCG can also be used for remote health management, connecting with IoT platforms to upload BCG data to the cloud for analysis and medical evaluation, supporting multi-user simultaneous monitoring and data comparison.
BCG is entirely contactless, capable of monitoring through mattresses, seats, or even floors without affecting user activity or sleep. It enables long-term continuous monitoring, making it suitable for high-risk patients or elderly individuals requiring 24/7 monitoring. It can acquire multiple parameters, including heart rate, respiration rate, HRV, and hemodynamic indicators. It offers high comfort and privacy, as users do not need to wear any devices, and there is no privacy concerns associated with cameras.
However, BCG technology also faces challenges such as signal noise interference. Factors like body movements, mattress elasticity differences, and external vibrations can affect data accuracy. Algorithm precision and standardization also require attention, necessitating enhanced AI and signal processing models to improve stability across different body types and postures. Furthermore, entering the clinical diagnostic field requires strict medical device certification and large-scale clinical validation. In the future, BCG will integrate with millimeter-wave radar, optical PPG, and other technologies to improve detection accuracy and environmental adaptability.
Next-generation high-performance contactless bio-monitoring solutions
Murata has introduced its improved 2nd-generation BCG solution, opening new possibilities for monitoring the status of individuals sleeping in hospitals and homes. It can detect biological signals such as pulse, respiration rate, and breath duration to determine bed occupancy and analyze sleep states.
Murata's solution includes a pre-programmed microcontroller (BCGMCU-D01) with algorithm and integrated with the low-noise SCL3300-D01 inclinometer in customers' PCB designs, forming a component-level solution targeted at software solution providers, service providers, and OEM system integrators, enabling BCG measurement integration into various healthcare products.
This new bed-mounted sensor utilizes BCG principles. When the heart beats, the bed undergoes subtle vibrations due to the body's movements. These weak signals are captured by an ultra-sensitive accelerometer and processed by algorithms embedded in the microcontroller to extract biological signals such as pulse. Through BCG products, sensor nodes can detect various biological signals, including pulse, respiration rate, heart rate variability (stress-related), stroke volume, and bed occupancy status.
The BCGMCU employs contactless measurement for continuous, interference-free monitoring. It offers a reference design approach with broad integration options, featuring low-power MEMS accelerometers with virtually unlimited lifespans. It is compatible with common manufacturing processes and includes an easy-to-use serial UART interface. It outputs beat-to-beat timing for calculating various HR and HRV metrics. Target applications include hospitals, elderly care facilities, and assisted living, enabling beat-to-beat heart rate detection, respiration rate monitoring, bed occupancy monitoring, sleep quality measurement, and stress and relaxation analysis. Murata's BCGMCU-D01 supports a 3.3V DC output voltage, a quiescent current of less than 6.7 mA, an output data rate (ODR) of 1 Hz, and a pulse detection range of 40-120 bpm.
High-performance, rugged 3-axis inclinometer
Murata's SCL3300 is a high-performance 3-axis inclinometer offering exceptional performance in tilt measurement. With compact dimensions of 7.6 × 8.6 × 3.3 mm (W × L × H), it supports four user-selectable measurement modes tailored to specific applications and requirements. It features ultra-low noise density and high resolution (0.001°/√Hz), an SPI digital interface, superior mechanical damping characteristics, an operating temperature range of -40 to 125°C, and a current consumption of 1.2 mA (at a supply voltage of 3.0–3.6V). It utilizes proven capacitive 3D-MEMS technology, delivering high performance and rugged design for applications demanding stability in harsh environments, such as leveling, tilt compensation, machine control, structural health monitoring, inertial measurement units (IMUs), robotics, and positioning and guidance systems.
Murata also offers the SCL3300 SERIES PCB, a digital accelerometer/inclinometer sensor board. This chip carrier PCB is equipped with the MEMS digital inclinometer SCL3300 series for easy product evaluation and design. Additionally, Murata provides the CA10H-SAL Sleep Analysis Library, which outputs instantaneous and cumulative overnight application data. It utilizes detected high- and low-frequency heart rate variability, respiration depth, and respiration variability for overnight recovery analysis. It automatically scores wakefulness, REM, light, and deep sleep stages and supports a sleep quality index based on detected recovery, REM, shallow and deep sleep scoring, and total sleep times. Currently supported operating systems include Ubuntu 18.04 and newer, as well as CentOS 6.0 and 7.
Piezoelectric film sensor for detecting biological signals like pulse and respiration
Murata has also introduced the piezoelectric film sensor (Picoleaf™), a flexible and thin sensor developed using Murata's proprietary piezoelectric technology. It can detect bending, twisting, pressing force, and vibration with high sensitivity. It saves mounted space and improves thinness, assembly performance, and durability compared to conventional sensors.
Moreover, the piezoelectric film used in Picoleaf is made from polylactic acid, which is synthesized from starch extracted from plants and fermented into lactic acid. Plants absorb carbon dioxide from the atmosphere to produce starch, making this material carbon-neutral and contributing to reducing global warming.
The Picoleaf detection circuit consists of an I/V converter and an amplifier circuit. When the piezoelectric film is warped (due to a pressure force or deformation), it generates polarization proportional to the degree of warping. The resulting charge is converted to voltage by the I/V converter and output as an analog signal. The voltage-converted signal is amplified and adjusted as needed for processing by general-purpose AD converters or CPUs.
Picoleaf's piezoelectric properties enable it to detect both "displacement direction" and "displacement velocity." For "mountain-fold" deformation, the displacement direction is output to the positive side of Picoleaf's reference voltage; for "valley-fold" deformation, it is output to the negative side. In addition to displacement direction, displacement velocity can be calculated from the peak voltage, which increases proportionally with displacement velocity. Furthermore, by leveraging the output inversion characteristic of Picoleaf sensors, push-and-release actions can be used as seamless switches in UIs. If Picoleaf is attached to an object with periodic vibrations, it can detect such vibrations and serve as a state detection sensor.
Picoleaf is ultra-thin (0.2 mm or less) and compact (2 × 10 mm), saving space even when combined with displays or touch panels. It can also be mounted on curved surfaces of intricately designed devices, including cylindrical shapes. Picoleaf can detect displacements as small as 1 micron, and a single sensor can measure pressure across the entire surface of a large display. It can detect unconscious muscle movements such as tremors, grasping, and pulse. Since it is non-pyroelectric, it avoids drift caused by heat (e.g., body temperature, sunlight, or semiconductors), resulting in lower noise and easier algorithm development. Additionally, the sensor itself consumes zero power, and the amplifier circuit can be designed for low power consumption (about 10 µA).
Picoleaf's light transmittance exceeds 90%, allowing installation in display panel areas requiring transparency. Combining touch panel UI functions with Picoleaf's pressure detection capabilities enables HMIs that differ from conventional touch panels, aligning more closely with human behavior principles. Picoleaf's thin, short, and flexible design allows for new features while maintaining design integrity. Its mounting flexibility easily addresses challenges like minimal space and curved surfaces, making it suitable for wearable devices to detect biological signals such as pulse and respiration.
Conclusion
Bio-monitoring solutions are rapidly advancing toward higher precision, multi-parameter analysis, real-time operation, and intelligence, playing an increasingly important role in medical diagnostics, health management, sports monitoring, and public safety. Murata's BCG solutions and Picoleaf piezoelectric film sensors enable 24/7 unobtrusive vital sign monitoring while providing real-time alerts for abnormal conditions, enhancing overall safety and health management efficiency. These innovations achieve all-scenario, round-the-clock vital sign tracking and health assessment, delivering more accurate, efficient, and sustainable health management solutions for individuals and society, propelling the healthcare industry into a new era of intelligence.