Microplastics detection and environmentally toxicity testing by multimodal optical metrology

Microplastics are small plastic particles with a size of less than 5 millimeters from cosmetics or results of abrasion and decomposition of plastic waste. The tremendous marine pollution by plastic particles and fibers and their increasing presence in the human environment from drinking water reservoirs to waste water demands for an environmental management and effective detection methods. The uptake of microplastics by living organisms may cause injuries of the gastrointestinal tract, trigger inflammation or cause cell toxicity by intrinsic particle properties or adsorbed pollutants. Thus, there is an urgent need for methods to identify microplastics in the environment as well as its sources and associated risks. The German joint research project MicroPlastiCarrier focusses on the development of new technologies for the optical detection and identification of microplastic particles in wastewater. In order to monitor particle uptake minimally-invasively in living organisms and cellular specimens in a label-free manner, we applied high resolution optical coherence tomography (OCT) and phase tomographic approaches. Moreover, multi-spectral digital holographic microscopy (DHM) is combined with innovative microfluidics to quantify morphological particle properties and their refractive index signatures at different wavelengths. Our results demonstrate that label-free optical metrology, as provided by OCT, DHM and tomographic phase microscopy (TPM), forms a promising powerful multi-functional toolbox for quantitative imaging to identify and determine the influence and risks of microplastics in the environment.