Signal Generation and Pattern-Based Detection: Microplastic and Nanoplastic Assays as Corollaries to PCR and ELISA

Abstract Detection of microplastics and nanoplastics (MNPs) is commonly approached through direct analytical measurement of particle composition or structure. In contrast, many established diagnostic systems operate through signal generation rather than direct visualization of the target. This work introduces an interaction-based assay framework in which measurable signal emerges from system-level dynamics within intact liquid samples.

Drawing conceptual parallels to Polymerase Chain Reaction (PCR) and Enzyme-Linked Immunosorbent Assay (ELISA), the method generates interpretable output through interaction-driven optical pattern formation. The approach is also analogous to pattern recognition in pathology, where spatial context and emergent structure provide diagnostic information. This framework establishes a complementary paradigm for MNP detection based on signal generation and pattern interpretation rather than direct particle detection.

This paper is also available at: https://doi.org/10.5281/zenodo.19521084

Figure 1. Comparison of signal-generation mechanisms in PCR, ELISA, and the interaction-based assay presented here. Detection in each case relies on an emergent, interpretable signal rather than direct visualization of the target.

1. Introduction Detection of microplastics and nanoplastics has traditionally focused on direct measurement approaches, including spectroscopic and analytical chemistry methods that aim to identify particles or their chemical composition at increasingly small scales.

However, across multiple domains of biology and medicine, detection is often achieved through signal-generating systems rather than direct observation. In these systems, the presence of a target is inferred through structured transformations that produce measurable output. For example, Polymerase Chain Reaction (PCR) generates signal through enzymatic amplification of nucleic acids, while Enzyme-Linked Immunosorbent Assay (ELISA) produces signal through binding cascades coupled to enzymatic readouts. In both cases, the target itself is not directly visualized.

These examples illustrate a broader principle: detection can arise from signal generation rather than direct observation.

2. Motivation: Limits of Direct Detection During development of assays for microplastic and nanoplastic systems, it became evident that direct detection of small particles presents practical challenges. At small scales and low concentrations, detection is constrained by resolution limits of imaging systems, signal-to-noise limitations, and sampling variability in heterogeneous environments. These constraints are particularly relevant in complex matrices such as environmental water or biological fluids.

Rather than attempting to directly resolve individual particles, this work adopts an alternative approach: to generate signal at the system level through interaction dynamics.

3. Signal Generation as a Detection Paradigm The assay framework presented here operates through interaction-driven signal generation. Upon introduction of a reagent, particles within the sample undergo aggregation, spatial redistribution, and interaction-mediated transport. These processes produce emergent optical patterns observable at the macroscopic level, including central clearing, radial gradients, and structured aggregation textures (Figure 1).

This paradigm is conceptually aligned with established signal-generating systems:

• PCR → amplification-based signal

• ELISA → binding cascade signal

• This system → interaction-driven emergent signal

In all cases, the signal is generated, not directly extracted.

Figure 1. Comparison of signal-generation mechanisms in PCR, ELISA, and the interaction-based assay presented here. Detection in each case relies on an emergent, interpretable signal rather than direct visualization of the target.

4. Pattern-Based Interpretation This framework is also analogous to interpretive approaches in pathology. In diagnostic pathology, interpretation often relies on spatial organization, morphological patterns, and contextual relationships rather than direct identification of individual molecular components.

Similarly, the present system produces structured optical patterns that encode information about the underlying particulate environment. Detection arises through pattern and signal, not isolated particle identification.

Figure 2. Representative transformation from direct visualization to signal generation. Left: Visual appearance of particulate matter in water. Right: Interaction-driven optical signal used for analysis, where detection arises from emergent patterns rather than direct particle identification.

5. Conclusion  This work presents a framework for microplastic and nanoplastic detection based on signal generation and pattern-based interpretation. By shifting from direct particle detection to interaction-driven signal formation, the system aligns with established assay paradigms such as PCR and ELISA, while extending these principles to physical interaction systems in complex media. This perspective supports the development of scalable, interpretable detection systems in both environmental and biological contexts.