Abstract
In order to implement POIROT in society in a form that is easily accessible to the general public, it is effective to create an inexpensive inspection device. Therefore, we have designed a device that can easily and accurately perform Lateral Flow Assay (LFA) using CAD. This device can be adjusted to perform inspections with minor design changes. We hope to optimize the design in the future by actually building and testing the device.
Introduction
The POIROT system we developed enables ordinary people to perform affordable glaucoma testing on their own, without relying on specialized institutions like hospitals. Since everyone is potentially at risk of developing glaucoma, this testing system will only realize its full value when used by a broad demographic. Early detection is particularly crucial for glaucoma, as it often lacks noticeable symptoms in the early stages, making the swift societal implementation of POIROT highly desirable. However, as POIROT is an innovative new testing system, there is no established technical foundation for its implementation. Therefore, alongside establishing and refining the reaction systems used in testing, it is essential to explore an integrated implementation method that envisions use in ordinary households. This also requires promptly connecting these efforts to concrete steps toward implementation, such as obtaining patents and establishing production lines.
In POIROT, the use of LFA (Lateral Flow Assay) for executing the test and displaying the results has been considered. In addition to allowing for simple and rapid testing, LFA is a technology used in various diagnostic devices currently available on the market, such as pregnancy tests, making it advantageous in terms of development costs and reliability. Moreover, by utilizing existing production infrastructure when implementing POIROT in society, we expect to be able to produce affordable and high-quality products. However, in the Wet Lab, cases where inaccurate test results were displayed under certain conditions have been observed, highlighting the necessity of controlling the sample solution to ensure proper flow rate and flow volume. (Refer to Wet Results_LFA.) Therefore, in order for a wide range of people to easily use this system, it is essential to have a device designed to perform accurate tests with simple operation. With this in mind, the design of the testing device was developed for societal implementation, considering the environments in which the system will actually be used.
Methods & Results
A concept design of the testing device was created, aiming to make it user-friendly and capable of executing the LFA under appropriate conditions. The device design was created using SOLIDWORKS, a CAD software by Dassault Systèmes SolidWorks Corporation. The device consists of two parts: a base part where the dropped sample solution flows from the reservoir onto the strip, allowing the LFA to be executed, and a lid part that encloses the strip inside the device and displays the positions of the Control Line and Test Line. By designing each part individually and assembling them in CAD, an integrated device design was made possible without having to create a physical prototype.
The designed device measures 100 mm in length, 40 mm in width, and 7 mm in thickness, with the aim of being small and affordable. The interior of the device is mostly hollow to minimize the amount of material used. The top surface has a hole for dropping the sample solution and a window for displaying the test result lines on the strip. The tear fluid collected from the user is placed in a separate container with a reaction solution, where the nucleic acid amplification reaction and CRISPR-Cas3 signal amplification reaction proceed at a set temperature. After a specified time has passed, 5 µL to 10 µL of the sample solution is dropped onto the device, allowing the solution to spread across the strip and conduct the test. Although some LFAs involve placing the strip vertically in the solvent, the device designed here places the strip horizontally. This prevents the test kit from tipping over during the LFA process and makes it easier to drop the sample solution, making the device more user-friendly for the general public.
This device includes two LFA strips, designed to individually test samples from both eyes, with each strip serving the same function. In addition to displaying the letters 'L' and 'R' at the respective positions where the sample solutions are dropped, the POIROT logo visually represents both eyes to indicate where to drop the solutions for each eye. This ensures that users can immediately identify which strip corresponds to the left or right eye.
A micro channel extends from the reservoir to the strip, allowing the solution to move through it and spread onto the strip. By using the micro channel, we can control the flow rate and flow volume of the solution, enabling a continuous supply of solution to the strip. By defining the point where the solution flows onto the strip, it is expected to make the device more quantitative than directly dropping the solution onto the strip. In the current design, the channel is straight, but by altering the width of the channel or making it meander, it is possible to adjust the flow rate, flow volume, and the time it takes for the solution to reach the strip from the reservoir. Therefore, the design can be flexibly modified based on experimental results to optimize conditions and improve reliability.
The device consists of two parts, (a) in combination and (b) in exploded view.
Conclusion & Future Prospect
In preparation for the societal implementation of POIROT, a testing device using LFA was designed in CAD. By using this device, it is expected that appropriate testing conditions for LFA can be met with simple operations, significantly enhancing the accessibility of healthcare for the general public.
The device designed this time has not yet been created, nor have any experiments using actual samples been conducted. Therefore, there is hope that future experiments using the created device, followed by cycles of improvement based on the results, will lead to the optimization of the device design. Additionally, creating precise structures such as micro channels requires expensive equipment like photolithography, high-precision glass etching, or stereolithography 3D printers, making detailed planning in the design stage essential. CAD design allows for easy dimension adjustments and the creation of input data for machining, and it can also be integrated with CAE for mechanical calculations and fluid simulations, making it an effective tool for accelerating device development.
Additionally, in mass production associated with societal implementation, injection molding using resin as the material is anticipated to be the primary manufacturing method. By creating molds, it becomes possible to produce devices at low cost with consistent quality, and the fabrication of micro channels is also feasible. Furthermore, using resin as the material makes disposal easier compared to materials like glass, and by utilizing biodegradable plastics and similar materials, it is expected to minimize environmental impact as much as possible.
