In recent years, laser and infrared detection technology has been rapidly developed. The material preparation, generation method, extinction performance test, and effect evaluation of multi-band smoke screens have garnered widespread attention. Traditional inorganic extinction materials, such as metal powder, red phosphorus, and expanded graphite, often possess drawbacks such as a narrow extinction band, high costs, combustibility, difficulty in degradation, a single release method, and environmental harm. Consequently, environmentally friendly extinction materials characterized by a broad extinction band, long duration, low preparation cost, pollution-free, and non-combustibility emerge as research hotspots both domestically and internationally.

Artificially controlled biomaterials, such as spores or hyphae, represent a new type of smoke screens medium, distinct from traditional inorganic extinction materials. Once released into the air, these biomaterials form smoke screens, altering light transmission properties through absorption and scattering. Hence, biomaterials can diminish the detection capabilities of visible, laser, and infrared detection systems and equipment, making them suitable for the photoelectric protection of critical targets or facilities. Biomaterials aggregated particles systems formed from tiny biological particles due to static electricity, collision, or adhesion, possess complex spatial structures and random orientations.

There is a significant progress in researching the extinction properties of biomaterials. Biomaterials can be prepared with attributes such as controllable morphology, cost-efficiency, ease of batch preparation, high impedance, environmental friendliness, and non-toxicity. Researchers have constructed structure models of spherical particles, typical non-spherical particles, monodisperse aggregated particles, and polydisperse aggregated particles and have analyzed their static extinction properties. Additionally, the dynamic extinction properties of biomaterials have been examined under varying wind speeds, surface roughnesses, and relative humidities. Regarding the differential extinction properties of viable and dead biomaterials, the activity ratio of biomaterials can be qualitatively determined. Although many advances have occurred, challenges persist in the simulation, testing, and enhancement of biomaterials' extinction characteristics. Thus, outlining current research on the extinction characteristics of biomaterials becomes essential, paving the way for future developments in safer and more eco-friendly broadband smoke screen materials.

First, the extinction characteristics of biomaterials are introduced, with absorption and scattering attributes based on the characteristics of complex refractive index. The calculation flowchart for the extinction characteristics of biomaterials is presented (Fig. 5), and characterization methods for different biomaterial structures are summarized. These structures include spherical single particles, typical non-spherical single particles, monodisperse aggregated particles, and polydisperse aggregated particles. Although the extinction properties are primarily determined by the composition and structural parameters of biomaterials (as shown in Fig. 6 and Fig. 9), other influential factors are examined. These factors are represented by biomaterial activity (Fig. 10), wind speed (Fig. 12), ground roughness (Fig. 13), and relative humidity (Fig. 14). Subsequently, static and dynamic testing methods for biomaterials are listed. In the static methods, the scanning electron microscope (SEM) test (Fig. 15) and infrared spectroscopy test (Fig. 16) are featured, while in the dynamic methods, the smoke box test (Fig. 17) and field test (Fig. 19) are included. In conclusion, emerging trends such as precise simulations of intricate spatial structures, analyses of factors influencing extinction characteristics, and standardization of extinction characteristics testing are emphasized.

In recent years, significant advancements have been observed in the study of extinction characteristics and test techniques of biomaterials. However, certain challenges persist that require attention in the forthcoming research, including the simulation of randomly oriented aggregation for biological particles, the multivariate analysis of dynamic extinction properties of biomaterials, and the standardization of extinction performance testing. Initially, given that biological particles generally possess irregular shapes and biological particle aggregations exhibit complex and variable structures, only a model accounting for the randomly oriented aggregation of these irregular particles can accurately represent the spatial structure of aggregated biological particles, ensuring precise calculations of the biomaterials' extinction properties. At this juncture, due to the absence of an established model for randomly oriented aggregation of irregular particles, simulations are restricted to particles with regular shapes. Furthermore, a comprehensive consideration of factors, such as wind speed, temperature, and atmospheric stability, becomes imperative, surpassing the simplicity of previous analyses affecting the extinction properties of biomaterials. Additionally, addressing issues of a low effectiveness-cost ratio and limited repeatability by standardizing the collection and analysis of experimental data emerges as a crucial research direction. Anticipated improvements for the near future include the development of a randomly oriented aggregation model for diverse irregular biological particles, enabling the study of extinction characteristics for non-spherical biological materials. There is also the need for accurate simulations and predictions of sedimentation diffusion of aggregated particles under varied meteorological conditions. This would involve the consideration of multiple influencing factors, the enhancement of specific organic groups performance and the integration of other material components to bolster biomaterial performance. Lastly, the establishment of clear evaluation tests and criteria for the extinction performance of biomaterials is crucial, ensuring experimental data are gathered and analyzed following a relatively consistent standard.