Design, Realization, and Test of Ultraviolet-C LED Arrays Suitable for Long-Lasting Irradiation of Biological Samples

Round 1

Reviewer 1 Report

1. The lack of novelty in research, the use of UV LED for sterilization and disinfection is very common.

2. In the simulation, the authors should clearly state what kind of LED array they wants to obtain and what parameters are used to judge whether the LED array meets the requirements, rather than directly giving the final design results.

3. Lack of control group in fin heat dissipation. 

4. Why only one array structure was selected for testing when two array structures were proposed in the manuscript

5. The discussion section was very poor, with only image comparisons and no data graphs or data analysis. The authors should provide detail to prove that UV LED can improve the antimicrobial properties of plants.

6. The manuscript does not provide corresponding data explanation for the proposed LED array being able to work for a long time. The author should add a lifespan test for this LED array.

7. The conclusion section is too long, and the focus and innovation points of the article's work should be highlighted.

No Comments

Author Response

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Reviewer 2 Report

Review of manuscript entitled “Design, realization and test of ultraviolet-C LED arrays suitable for long-lasting irradiation of biological samples” by Sarah Bollanti et al.

Manuscript gives a description of the application of LEDs light sources on fruits to stimulate defensive metabolites that help them to resist pathogen attack. It describes calculation and experimental methods. In particular the experimental methods are well described with details. Temperature parameter is considered and an application to lemon samples is given. It is suggested that these LEDs sources could replace the mercury lamps used at present.

In the conclusion section it is mentioned that also the method has been tested with other fruits like apples, basil and kiwis, however no specific results have been presented. It is suggested that results using these fruits, basil, apples and kiwis, should be presented with details.

Author Response

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Reviewer 3 Report

The paper presents a comprehensive study on the electrical and optical design, assembly, and experimental characterization of two compact arrays of short-wavelength ultraviolet (UV-C) light-emitting diodes (LEDs). The authors successfully achieved effective thermal management, allowing for long-lasting irradiations without significant deterioration of UV-C emission. These compact UV-C LED arrays were used for irradiation tests aimed at enhancing the resistance of plants and fruits to pathogen attacks through the biosynthesis of defensive metabolites. The study also explores the possibility of implementing these compact UV-C sources on robotic systems to reduce pesticide use in agricultural crops.

The authors illustrated the software-assisted design, implementation, and experimental validation of the LED arrays suitable for long-lasting near-field UV-C irradiation. The arrays consist of 20 and 38 LEDs, powered by constant current and equipped with active and passive control systems. The maximum powers emitted by the arrays are 0.7 W and 1.4 W, respectively, at a wavelength of 276 ± 5 nm (FWHM). The design allows for adjustable UV-C power emission, catering to user-specific needs. While the prototype array's total cost was around $500, a mass-produced version would be significantly cheaper.

The characteristics of the arrays were verified through experimental measurements and comparison with dedicated simulation software. The simulation code provided a powerful tool for designing optimized arrays for specific applications, as it allowed calculating the emitted light intensity at any point in space based on the radiation emitted by each source.

The authors demonstrated effective thermal management of the LED arrays using a combination of a fan-integrated pin-fin heat sink, a 3-mm-thick Al plate, and burst mode operation. Even during half a day of irradiation (4 hours of effective lighting), the temperature of the LEDs remained below 40 °C, thanks to a heat flux of 32 kW·m-2. This thermal management approach enabled the treatment of multiple biological samples, generating sufficient data for statistical analysis of their response. The constant current delivered by the power supply played a crucial role in maintaining the UV-C emission close to the initial level, even in the presence of temperature gradients.

The devices were used for various long-lasting irradiations, demonstrating the induction of hormesis in apples, lemons, basil, and kiwi. By applying a UV-C dose of 300 J·m-2 over a time interval of 3 to 14 seconds, the authors observed the production of metabolites that inhibited pathogen growth. This preventive irradiation approach with the UV-C LED arrays offers an integrated control method for crop diseases, potentially reducing the reliance on pesticides in intensive agriculture.

The authors also discussed their plans to integrate the LED arrays into an existing autonomous robotic system, replacing mercury lamps. This modification would enable the robotic system to radiate UV-C light on plants in the open field and sanitize surfaces or instruments in hostile environments.

Overall, the paper provides a detailed account of the design, assembly, and experimental characterization of compact UV-C LED arrays for near-field irradiation. The study's findings have significant implications for agriculture, offering a potential solution to reduce pesticide usage and enhance crop disease control. The research opens up avenues for further exploration and application of UV-C LED arrays in diverse fields, including robotics and sanitation.

The studies are interesting and promising, but Authors need to expand on the introduction and add more topical and up-to-date research articles to the references. The introduction should contain a description of research carried out by other authors. Most of the references contains websites, which significantly reduces the value of a scientific article.

Author Response

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Round 2

Reviewer 1 Report

no comments

no comments

Reviewer 3 Report

I accept article in present version.