Application Cases

Experiment Name: Experimental Study on the Luminescent Characteristics of Electroluminescent Fibers

Research Direction:
With the rise of flexible electronic products, smart sensors, and smart wearables, flexible electroluminescent devices have experienced vigorous development. Flexible electroluminescent fibers, with their portability, flexibility, and weavability, bring significant potential to the field of visual sensing. However, limitations such as the complex fabrication process of their mostly dual-electrode structure result in challenges in cost, device uniformity, sensitivity, and flexibility. Single-electrode electroluminescent fibers consist of a conductive layer, a dielectric layer, and a luminescent layer, with an emission wavelength of 456 nm, offering excellent mechanical properties, luminescent performance, and flexibility. These fibers can be applied to the visual sensing of solutions, achieving a recognition sensitivity of 0.001% (mass fraction) for sodium chloride concentration, demonstrating outstanding sensitivity, which is significant for sweat detection and biological applications. The luminescent fibers can be further woven into luminescent textiles, whose breathability and mechanical properties are comparable to those of ordinary commercial fabrics, enabling visual sensing of different sodium chloride concentrations. In the field of wearable devices, wirelessly driven single-electrode electroluminescent fibers hold great potential for visual display and communication functions. Current wearable sensors mainly come in two forms: thin films and fibers. Compared to thin-film devices commonly used in flexible electronics, fiber-based electronic devices exhibit higher flexibility and breathability, releasing stress during fabric deformation to prevent local stress concentration, thus offering longer service life and superior performance. In liquid sensing and monitoring, fiber-based electronic devices can achieve 360° full contact with liquid surfaces, demonstrating superior monitoring performance.

Experimental Purpose:
To validate the luminescent characteristics of materials under different frequencies and electric fields.

Test Equipment:
Signal generator, Voltage amplifier, Oscilloscope, Transmission electron microscope, Scanning electron microscope, Spectrometer, etc.

Experimental Process:
The excitation signal generated by the signal generator is amplified by the ATA-214 high-voltage amplifier and applied to both ends of the electrodes of the luminescent material, creating an electric field within the material. By varying the frequency of the AC signal with the signal generator and adjusting the electric field strength with the amplifier, the luminescent characteristics of the material under different voltages and frequencies are studied. When a voltage is applied between the two electrodes of the material, an electric field is formed within the material. This electric field excites electrons in the material, enabling them to gain sufficient energy. Under the influence of the electric field, charge carriers (including electrons and holes) migrate. Electrons move from the negative electrode (N-type semiconductor) to the positive electrode (P-type semiconductor), while holes migrate in the opposite direction. When electrons and holes meet and recombine in a specific region of the material, energy is released. The released energy is emitted in the form of photons, producing visible light. During this process, the transition, change, and recombination of electrons between energy levels are key to luminescence.

Experimental Results:
As shown in Figure 1.1(d), the luminescent power density varies by only 0.5 nW/cm² within 2000 ms. As shown in Figure 1.1(e), the emission spectrum of the luminescent fibers measured under different voltages indicates an emission wavelength of 456 nm. Figure 1.1(f) shows the chromaticity diagram of the luminescent fibers, emitting blue light. The luminescent power of the fibers measured under different voltages in air is shown in Figure 1.1(g).

Figure 1.1: Luminescent performance testing of single-electrode electroluminescent fibers.
(a) Luminescence of fibers in water;
(b) Magnified view of fiber luminescence in water;
(c) Luminescence of fibers under bending;
(d) Luminescent power density under 60° and 120° bending;
(e) Emission spectra under different voltages;
(f) Chromaticity diagram;
(g) Luminescence under different voltages;
(h) Luminescence under different frequencies;
(i) Luminescent intensity measured at different angles.

Figure 1.2: Physical images of luminescence in salt solutions of different concentrations.

Na⁺ and Cl⁻ are the most abundant ions in sweat. Single-electrode electroluminescent fibers can detect sodium chloride concentrations ranging from 0.17 to 5.128 mmol/L (mass fraction 0.001% to 0.03%), while the concentration range of Na⁺ and Cl⁻ in human sweat is 1 to 10 mmol/L. It has been reported that when the sodium chloride concentration in women exceeds 4 mmol/L, the risk of cystic fibrosis in their offspring significantly increases. However, traditional sweat test results are output as electrical signals, which need to be converted into numbers or curves for interpretation, making direct visual detection impossible. As ion concentration increases, more energy is required for ion deflection under an alternating electric field, leading to a reduction in the electric field strength applied to the luminescent material. This, in turn, weakens the luminescent intensity, causing the luminescent intensity of the fibers to vary with concentration.

Voltage Amplifier Recommendation: ATA-214 High-Voltage Amplifier

Figure: ATA-214 High-Voltage Amplifier Specifications

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