Integrated laser Doppler blood flowmeter designed to enable wafer-level packaging

Area of Science:

• Biomedical Engineering
• Optical Sensing
• Microsystems Engineering

Background:

• Accurate tissue blood flow measurement is crucial for diagnosing and monitoring various medical conditions.
• Existing laser Doppler blood flowmeters can be bulky, power-hungry, and suffer from optical power loss.
• Development of miniaturized, efficient, and high-performance blood flow sensors is an ongoing need in biomedical research.

Purpose of the Study:

• To propose and validate a novel sensor structure for an integrated laser Doppler blood flowmeter.
• To achieve reduced optical power loss, small size, and low power consumption in the blood flow sensor.
• To demonstrate the high linearity and wide dynamic range of the proposed sensor for tissue blood flow measurement.

Main Methods:

• Fabrication of a new sensor structure using silicon micromachining techniques.
• Integration of two silicon cavities, each housing a photodetector (PD) and a laser diode.
• Assembly with a silicon lid featuring a converging microlens to complete the sensor package.
• Performance evaluation using a model tissue blood flow system.

Main Results:

• The proposed sensor structure significantly reduced optical power loss.
• The integrated sensor achieved a notably small size and low power consumption.
• Measurements demonstrated high linearity in assessing blood flow.
• A wide dynamic range for tissue blood flow measurement was confirmed.

Conclusions:

• The novel micromachined silicon sensor structure is suitable for integrated laser Doppler blood flowmeters.
• The sensor's design offers advantages in terms of size, power efficiency, and optical performance.
• The validated high linearity and wide dynamic range indicate its potential for effective clinical and research applications.