Hardware

mascot-hardware

Introduction

As a part of our aim to design a cheap, accessible, accurate and quick-acting lateral flow test (LFT) tailored to point of care (POC) testing, it was important we looked into the functionality and cost behind the hardware of a LFT. We learnt the test strip and cassette of a LFT play crucial roles in its functionality, and we realised we could not create an effective LFT focusing on synthetic biology alone. After reflecting upon this, our goal was to select a test strip best suited for our detection method, alongside design a cassette optimised to this strip whilst allowing for simultaneous testing of separate biomarkers.

Due to time constraints during wet lab, we were not able to explore details about our cyclic chain displacement reaction (CCDR) that would have fully informed test strip and cassette design. Despite this we believe the iGEM community can take this work much further and wanted to facilitate this. Directly building upon a cassette model previously designed from the 2022 University of Virginia iGEM team (1), we have made a simple, easy-to-edit base cassette model able to hold two test strips. Throughout this page we aim to introduce design considerations for both the test strip and cassette model, which can be directly applied to this base model.

LFT Cassette Model and Features

Our lateral flow test (LFT) cassette represents a significant advancement in point-of-care diagnostic technology. The cassette design incorporates several key features that enhance usability, reliability, and accuracy of test results.

Adaptations

  • Before settling on the CCDR detection method, enabling multiplex biomarker testing on a single test strip, our initial method was to separately test for fold changes in two different biomarkers on two different test strips. This initial method is reflected in the cassette model, where it was adapted to hold two test strips for two simultaneous tests (Figure 1A).
  • Internal barriers between the two test strips were included to avoid contamination between the two samples, this barrier is minimal yet functional to keep material usage and by extension costs down (Figure 1B).
  • The sample port was moved to align with the sample collection well within the test (Figure 1C and 1D). This well was originally designed to prevent excess sample spillage within the cassette, in the original model the sample port was offset from the centre of the well creating room for spillage (1).
Cassette Model Design

Figure 1. View of the LFT cassette model and the different adaptations made using Tinkercad. (A) The top piece of the cassette adapted with two sample ports and result windows for two simultaneous tests. (B) The bottom piece of the cassette adapted with two test strip holders and wells which are internally isolated. (C) The cassette model assembled in Tinkercad with no misalignments with internal and external features. (D) A comparison of well alignment between the original model (blue) and our adapted model (grey).

Features

Key features include:

  • Compact, portable design for easy handling
  • Clear visual indicators for test results
  • Robust construction for field use
  • Standardized dimensions for compatibility
  • Printing time:
  • Filament usage:
  • Test strip dimensions: Length: 5.50mm Height: 55.00mm Width: 1.00mm

Downloadable STL Files:

LFT Test Strip Design Considerations

Not only does a LFT test strip contain the components necessary for the control and test line to form, it also plays a major role in controlling the flow of sample down the test. This is an important variable to optimise as different flow rates impact the speed and sensitivity of a test (2), alongside the volume of sample and reagents required for the test (3). Here we will discuss some of the considerations required to optimise these features.

The faster a sample flows down a test strip, the sensitivity of the test disproportionally decreases (2). This is because increasing flow leaves less time for interactions to form between biomarkers and detectors, as well as leaving less time for detectors to interact with control and test lines (2). A faster flow rate can also require larger sample and reagent volumes which can increase the cost of the test (3). On the other hand, the faster the sample flows down the test, the quicker results can come through. Minimising the time required for an accurate readout creates a test more applicable to a POC environment, where it is deployable on a larger scale.

Features of a test that can influence the flow rate include: sample viscosity, volume of sample and reagents, properties of the strip's materials such as porosity and the dimensions of the test strip (3). Each of these features can be tailored to the detection method of the LFT to create the most ideal final product. Some properties of the detection method to consider include: the time required for an accurate readout, signal intensity, sample type, and concentrations of detectors required. For example, tests with high signal intensity in a short period of time may not require a slower rate of flow, which may only increase the time required for a readout.

The test strip and components of the detection mechanism can also influence other important aspects of a LFT test, storage conditions required to retain long-term functionality is a good example of this (4). For more information and detail about LFT design considerations we encourage reading the references listed at the bottom of this page.

LFT Cassette Design Considerations

Cassettes for LFTs serve to safely house the test strip for portability, prevent sample contamination, denote positions of test and control lines in a results window, and further enhance the performance of a test strip. Designed after the properties, materials and dimensions of a test strip have been selected (5), cassettes prevent samples flowing elsewhere but down the test strip and also influence the rate of flow. Elevation, compression and pressure points are often engineered at specific points across the cassette to help regulate flow across the LFT, specific to the test strip used (5). This offers a further opportunity to optimise the flow and therefore a number of other crucial properties of a LFT as discussed in the above section. For further details and information about LFT cassette design considerations please see the references at the bottom of the page.

References

  1. 2022.igem.wiki/virginia. Contribution [Internet]. 2022 [cited 2025 Sep27]. [2 screens]. Available from: https://2022.igem.wiki/virginia/contribution
  2. Mansfield MA. Design Considerations for Lateral Flow Test Strips [Internet]. 2015 [cited 2025 Sep27]. [32 pages]. Available from: https://www.merckmillipore.com/INTERSHOP/static/WFS/Merck-Site/-/Merck/en_US/Freestyle/DIV-Divisional/Events/pdfs/lateral-flow-presentations/design-considerations-for-lateral-flow-test-strips.pdf
  3. Millipore Sigma. Optimising Lateral Flow tests [Internet]. [cited 2025 Sep27]. [9 pages]. Available from: https://content.knowledgehub.wiley.com/secure_file.php?path=/wp-content/uploads/2025/05/Optimizing-Lateral-Flow-Tests-Membrane-Selection-and-Performance-Insights_MilliporeSigma.pdf
  4. Merck. Lateral Flow Test: Design, Materials and Manufacturing Insights [Internet]. [cited 2025 Sep27]. [3 screens]. Available from: https://www.sigmaaldrich.com/GB/en/technical-documents/technical-article/clinical-testing-and-diagnostics-manufacturing/ivd-manufacturing/lateral-flow-test-insights?msockid=2e562ae792f26fa437ed386296f26905
  5. Lateralflowsolutions.com. Cassette Selection and Specifications [Internet]. 2025 [cited 2025 Sep27]. [3 screens]. Available from: https://www.lateralflowsolutions.com/en/CassetteSelectionandSpecifications-n3237.html