Plastiverse

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Tap Trap: Open Hardware for Sampling Microplastics in Tap Water

Moore Institute for Plastic Pollution Research
https://mooreplasticresearch.org/tap-trap/
  • Open Data: No
  • Access: Open Source

Description

Tap Trap: Open Hardware for Sampling Microplastics in Tap Water (and a Classroom-to-Community Monitoring Workflow)

Tap Trap is a practical, low-barrier tap-mounted microplastics sampling device developed by the Moore Institute for Plastic Pollution Research that enables consistent collection of microparticles from household taps for downstream microplastics analysis. In a community-based learning (CBL) project in Los Angeles, Tap Trap was used alongside standard lab methods (filtration, Nile Red staining, fluorescence microscopy) to detect and characterize microplastics from home tap water and compare results to river-water samples .

What is the Tap Trap?

The Tap Trap is a sampling device used to collect microparticles from tap water, with a removable 20 µm filter that can be inspected and processed for microplastics confirmation. In the documented LA CBL project, particles on the Tap Trap filter were visible under brightfield microscopy and then confirmed as microplastics via Nile Red staining + fluorescence microscopy .

Core components (what you actually need)

1) Tap Trap device + removable filter

  • 20 µm filter removed from the device for microscopy-based assessment

2) Consumables and filtration materials (used in the documented application)

The LA CBL workflow used common microplastics lab supplies including:

  • Polycarbonate (PCTE) membrane filters (e.g., 0.2 µm / 47 mm) and PTFE membrane filters (e.g., 0.45 µm) for vacuum filtration steps in water sample processing
  • Basic wet-lab glassware and vacuum filtration setup for concentrating particles onto membranes

3) Screening chemistry: Nile Red staining

The supporting workflow documents a Nile Red approach for fluorescent screening of suspected microplastics, including:

  • A 1 mg/mL Nile Red stock solution in acetone and a working solution prepared with n-hexane, with dark storage to prevent photodegradation
  • Example staining workflow: applying working solution to a filter and incubating 30 minutes in the dark, then allowing solvent to evaporate before imaging (or staining on the filtration unit and rinsing)
  • Storage guidance: stock solution stored ≤6 months, working solution ≤2 months (dark, 4 °C)

4) Imaging and measurement

The documented application used an Echo Revolve fluorescence microscope to image samples in brightfield and fluorescence (Nile Red channel), using multiple objectives (4x–40x) . Students counted fluorescing particles and measured size along the longest axis and particle area with microscope software .

What Tap Trap enables

Tap Trap supports collection and reporting of:

  • Particle counts (e.g., brightly fluorescing Nile-Red-positive particles)
  • Morphology categories (e.g., fragment/fiber style categorization; the SI references morphology categories and subsampling guidance)
  • Particle size metrics (longest-axis length; area)
  • Clear linkage to site metadata (home tap location, sampling event), which is essential for cross-study comparisons

Applications (where Tap Trap fits)

Tap-water microplastics screening at the point of use

In the LA CBL project, students used Tap Trap to collect home tap samples from multiple neighborhoods (e.g., Pasadena, Highland Park, West Covina, Alhambra) and then verified microplastics via Nile Red fluorescence microscopy .

Comparative watershed investigations (tap vs. surface water)

The same project collected 1 L river-water samples (Los Angeles River, Lewis McAdams Park) and processed them with sieving, filtration, digestion, and Nile Red staining to compare with Tap Trap-derived tap samples .

Education + community advocacy

The SI explicitly documents the Tap Trap workflow as part of a community-based learning experience where students used generated data in scientific communication and advocacy efforts .

Documented processing workflow (from the Tap Trap application)

A representative end-to-end approach in the SI includes:

  • Water collection → sieving/filtration → (as needed) biological digestion → Nile Red staining → fluorescence microscopy
  • For river-water samples, the SI describes hydrogen peroxide digestion performed in a vacuum filtration setup (e.g., 30% H₂O₂ incubation at 37 °C for ~16 hours in one procedure) to address biological matter before imaging .
  • For Tap Trap, the 20 µm filter can be removed and directly examined; Nile Red staining + fluorescence microscopy were used to confirm plastics .

Important considerations (QA/QC, safety, and “what Tap Trap does not do”)

Tap Trap captures particles; identification is downstream

Tap Trap is a sampling front-end. The SI emphasizes that after screening and quantification by microscopy/Nile Red, additional analytical methods such as FTIR or Raman can be used to chemically identify polymers .

Solvent safety and light sensitivity

The SI notes Nile Red staining solutions involve solvents (acetone, n-hexane) and were handled in a functioning fume hood, and solutions were protected from light to reduce photodegradation .

Avoiding over-claims from fluorescence-only screening

Nile Red + fluorescence microscopy is a powerful screening/confirmation approach for suspected plastics in the documented workflow, but polymer identity ultimately requires spectroscopy (FTIR/Raman) if you need definitive chemical classification .

How to use Tap Trap with Plastiverse (recommended complementary resources)

Tap Trap projects become far more valuable when results are standardized, validated, and shareable across teams. We recommend exploring these resources related to these topics:

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