Application Cases

Currently, blood glucose detection technologies can be categorized into three main types: invasive blood glucose detection, minimally invasive blood glucose detection, and non-invasive blood glucose detection. Invasive blood glucose detection, commonly known as blood sampling testing, is widely used in hospitals for routine blood tests and remains the most prevalent and mature technology. However, due to the risk of wound infection caused by frequent blood sampling, blood glucose detection technology is gradually evolving from invasive to minimally invasive/non-invasive methods.

Experiment Name: Design and Experiment of Photoacoustic Blood Glucose Signal Acquisition System

Experimental Principle:
Based on the photoacoustic effect: glucose molecules are thermally excited under a single-wavelength pulsed laser at 1064 nm, leading to thermal expansion and generating ultrasonic waves (photoacoustic blood glucose signals). These ultrasonic waves are received by a focused ultrasound probe, converted into electrical signals, and then amplified and acquired through data collection. The core theoretical verification relies on meeting the condition that the laser pulse width is significantly shorter than the thermal relaxation time and stress relaxation time, ensuring that the laser energy is fully converted into photoacoustic signal energy. Additionally, the peak power density of the laser spot is calculated to verify that the signal intensity is sufficient for detection.

Experimental Block Diagram:

Experimental Setup Photos:

Experimental Procedure:

System Setup:

• Optical components: Pulsed laser → coupling lens → multimode fiber → objective lens;

• Acoustic components: Plastic tube → focused ultrasound probe → preamplifier (60 dB gain, amplifying weak signals) → data acquisition card.

Solution Preparation:
A high-precision electronic balance is used to prepare glucose solutions of varying concentrations (0–435.6 mg/dL). The actual concentration is calibrated using an invasive blood glucose meter (Sinocare GA-3).

Signal Acquisition:

• The test solution is added dropwise to the photoacoustic cell, and the laser is adjusted to vertically incident the liquid surface.

• The photoacoustic signal is recorded on an oscilloscope. After the solution is aspirated, the concentration is measured and recorded using an invasive blood glucose meter.

• This process is repeated, ultimately yielding 192 valid photoacoustic signal samples. Variations across multiple experiments are corrected by normalizing with pure water signals as a reference.

Application Directions:

• Time-frequency feature-based algorithms (S-transform + Teager-Kaiser main energy)

• Waveform feature-based algorithms (forced vibration equation + evidence regression)

• Evidence fusion algorithm based on self-similar focal points

• Biomedical engineering research

• Signal processing teaching cases

• Foundation for subsequent technological iterations