Wearable biosensors are transforming personal healthcare by enabling real-time, non-invasive monitoring of vital physiological and biochemical markers. While first-generation wearables focused on physical metrics like heart rate and body temperature, next-gen systems now analyze biomarkers such as glucose, electrolytes, hormones, and pH levels from biofluids like sweat, saliva, interstitial fluid (ISF), and tears.
The Challenge: Power-Efficient Fluid Handling
Despite these advancements, integrating miniaturized and energy-efficient fluidic systems remains a major challenge. Traditional microfluidic platforms often rely on external pumps or batteries, which limit portability and long-term use.
The Solution: Capillary Microfluidics
Capillary microfluidics offers a breakthrough by using engineered surface properties and smart channel geometries to autonomously move fluids—no external power required.
- Material Design:
- Constructed from layered hydrophilic/hydrophobic materials
- Biofluids are drawn directly from the skin via contact inlets or wicking textiles
- Fluid Control:
- Fluids are guided into sensing zones with high precision
- Prevents contamination, backflow, and saturation
- Evaporative outlets and optimized geometries ensure consistent, long-term operation
Multimodal Sensing Capabilities
Capillary-based wearables support both electrochemical and optical biosensing:
| Detection Method | Mechanism | Advantages |
|---|---|---|
| Electrochemical | Uses electrodes to detect redox reactions | High sensitivity, low power |
| Optical | Employs colorimetric or fluorescent reagents | Visual feedback, multiplexing |
Advanced materials like molecularly imprinted polymers (MIPs) and aptamers enhance specificity, stability, and sensor longevity, making these platforms ideal for continuous health monitoring.
A Holistic Review: Beyond Materials and Electronics
Unlike earlier reviews that narrowly focus on sensing components, this work provides a comprehensive assessment of capillary microfluidics as the core fluid-handling technology in wearable diagnostics.
Key Differentiators:
- Chrono-sampling vs. Continuous Flow: Understanding sampling dynamics for different use cases
- On-body vs. Off-body Analysis: Flexibility in data collection and processing
- Sensor Integration: Bridging fluidics with biosensing for robust performance
Toward Autonomous, Clinically Ready Diagnostics
Capillary microfluidics enables a new generation of smart, autonomous wearable devices that are:
- Miniaturized and power-free
- Capable of multimodal sensing
- Clinically scalable and user-friendly
These innovations pave the way for decentralized health monitoring—whether at home, in clinical settings, or on the move.
