7 type of Biosensors in Wearables: ECG, EEG, PPG, and More (Part 1)

Wearable technology is transforming healthcare by enabling continuous monitoring of vital health parameters. Among the various biosensors integrated into wearable devices, three key types are Electrocardiography (ECG), Electroencephalography (EEG), and Photoplethysmography (PPG). In this article, we will explore what these biosensors are, their types, their applications, and their role in modern wearable devices.

1. Electrocardiography (ECG)

Electrocardiography (ECG) is a medical technique used to measure the electrical activity of the heart over time. It records the heart’s rhythm and electrical impulses, helping in the diagnosis of various cardiovascular conditions.

Types of Electrocardiography

There are several types of electrocardiography, each suited for different medical and wearable applications:

• Resting ECG: Conducted while the patient is at rest to check for heart conditions.
• Exercise ECG (Stress Test): Performed while the patient engages in physical activity to assess heart function under stress.
• Holter Monitoring: A continuous ECG recording over 24–48 hours using a portable device.
• Wearable ECG Sensors: Integrated into smartwatches and patches for real-time heart monitoring.

What Does Electrocardiography Measure?

Electrocardiography measures the heart’s electrical signals, providing insights into:

• Heart rate and rhythm: Determines if the heart is beating at a normal pace.
• Arrhythmias (irregular heartbeats): Detects abnormalities such as atrial fibrillation.
• Heart attack detection: Identifies ischemic changes and myocardial infarction.
• Effects of medications on the heart: Helps monitor drug-induced changes in heart function.

Biometric Data:

• Heart Rate Variability (HRV): Indicates autonomic nervous system balance and stress levels.
• QT Interval & ST Segment: Used to detect heart diseases and electrolyte imbalances.
• P, QRS, and T Waves: Reflects the different phases of heart electrical activity.

Wearable ECG technology is increasingly used for remote patient monitoring and fitness tracking, helping individuals manage their heart health effectively.

2. Electroencephalography (EEG)

Electroencephalography is a technique used to record the electrical activity of the brain. It is widely used in diagnosing neurological disorders and studying cognitive functions.

Types of Electroencephalography

There are different types of electroencephalography used in medical and consumer applications:

• Routine EEG: A short-duration test (20–40 minutes) to analyze brain activity.
• Ambulatory EEG: Continuous monitoring over a day or more to detect intermittent brain activity changes.
• Sleep EEG: Conducted during sleep to diagnose sleep disorders and epilepsy.
• Wearable EEG Headsets: Portable EEG devices for real-time monitoring of brain activity in various applications.

Electroencephalography Application

Electroencephalography has various applications in healthcare and beyond:

• Neurological Disorder Diagnosis: Helps detect epilepsy, seizures, and other brain disorders.
• Sleep Monitoring: Assists in studying sleep patterns and diagnosing sleep disorders.
• Cognitive Performance Tracking: Used in neurofeedback training and brain-computer interfaces.
• Mental Health Assessment: Helps monitor stress, anxiety, and mental well-being.

Biometric Data:

• Brainwave Patterns (Delta, Theta, Alpha, Beta, Gamma): Used for analyzing cognitive and emotional states.
• Event-Related Potentials (ERP): Helps in detecting brain responses to stimuli.
• Neurofeedback Metrics: Used in focus training, relaxation therapy, and stress monitoring.

Wearable EEG devices are gaining traction in cognitive health and mindfulness applications, making brain monitoring more accessible to consumers.

3. Photoplethysmography (PPG)

Photoplethysmography (PPG) is an optical technique used to measure blood volume changes in microvascular tissue, widely applied in wearable devices for heart rate and oxygen saturation monitoring.

Application of Photoplethysmography (PPG)

Photoplethysmography (PPG) is widely used in wearable and medical devices for health monitoring. It enables heart rate tracking, blood oxygen (SpO₂) measurement, and sleep analysis. A key advancement is Photoplethysmography Blood Pressure estimation, where PPG sensors analyze pulse wave velocity and arterial stiffness for non-invasive monitoring. Additionally, PPG supports cardiovascular health assessment, respiratory rate tracking, and stress monitoring, making it essential for personalized healthcare.

Infrared Photoplethysmography PPG Sensors

Infrared photoplethysmography PPG sensors use near-infrared light to penetrate deeper into the skin, providing more accurate readings of blood flow and oxygen saturation. These sensors are commonly integrated into smartwatches and fitness trackers for continuous health monitoring.

Photoplethysmography Application

Photoplethysmography has several applications in wearable health monitoring:

• Heart Rate Monitoring: Tracks beats per minute in fitness and health applications.
• Oxygen Saturation (SpO2) Monitoring: Measures blood oxygen levels, crucial for detecting respiratory issues.
• Blood Pressure Estimation: A non-invasive alternative to traditional blood pressure cuffs.
• Fitness and Recovery Tracking: Helps users optimize workouts and monitor cardiovascular health.

Biometric Data:

• Pulse Wave Velocity (PWV): Helps estimate arterial stiffness and blood pressure trends.
• Blood Volume Pulse (BVP): Provides information on cardiovascular health and stress response.
• Heart Rate Variability (HRV): Assesses autonomic nervous system function and stress levels.

With advancements in sensor technology, PPG-based wearable devices are becoming more accurate and reliable for real-time health tracking.

On the market, ECG, EEG, and PPG are the most used biosensors in wearable products. However, other biosensors such as Bioimpedance Analysis (BIA), Temperature Sensors, Galvanic Skin Response (GSR), and Accelerometers also play a crucial role in health monitoring. These additional biosensors will be explored in Part 2 of this series.

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At ITR VN, we specialize in MedTech and Digital Health, providing full-cycle development from Proof of Concept to Mass Production. With expertise in biosensor integration, we help clients build high-precision wearable health solutions that meet FDA compliance and ISO 13485 certification.

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