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Per- and poly-fluoroalkyl substances (PFAS) are a group of organo-fluorine compounds that have been broadly used in consumer and industrial products spanning virtually all sectors. They can be found as surfactants, coatings and liners, polymer additives, fire retardants, adhesives, and many more. The chemical stability of the carbon fluorine bond and amphiphilic nature of PFAS result in their persistence and mobility in the environment via soil porewater, surface water and groundwater, with potential for adverse effects on the environment and human health. There is an emergent and increasing requirement for fast, low-cost, robust, and portable methods to detect PFAS, especially in the field. There may be thousands of PFAS compounds present in soil and water at extremely low concentration (0.01–250 ppb) that require measurement, and traditional technologies for continuous environmental sensing are challenged due to the complexity of soil chemistry. This paper presents a comprehensive review of potentially rapid PFAS measurement methods, focused on techniques for representative sampling of PFAS in porewater from contaminated soil, and approaches for pre-treatment of porewater samples to eliminate these interferences to be ready for PFAS-detecting sensors. The review discusses selectivity, a key factor underlying pre-treatment and sensing performance, and explores the interactions between PFAS and various sensors. PFAS chemical nano-sensors discussed are categorized in terms of the detection mechanism (electrochemical and optical). This review aims to provide guidance and outline the current challenges and implications for future routine PFAS sensing linked to soil porewater collection, to achieve more selective and effective PFAS sensors.

Additive manufacturing (AM, also commonly termed 3D printing) is progressing from being a rapid prototyping tool to serving as pillar of the Industry 4.0 revolution. Thanks to their low density and ease of printing, polymers are receiving increasing interest for the fabrication of structural and lightweight parts. Nonetheless, the lack of appropriate standards, specifically conceived to consistently verify the tensile properties of polymer parts and benchmark them against conventional products, is a major obstacle to the wider uptake of polymer AM in industry. After reviewing the standardisation needs in AM with a focus on mechanical testing, the paper closely examines the hurdles that are encountered when existing standards are applied to measure the tensile properties of polymer parts fabricated by fused filament fabrication (FFF, aka fused deposition modeling, FDM), which is presently the most popular material extrusion AM technique. Existing standards are unable to account for the numerous printing parameters that govern the mechanical response of FFF parts. Moreover, the literature suggests that the raster- and layer-induced anisotropic behaviour and the complicated interplay between structural features at different length scales (micro/meso/macro-structure) undermine pre-existing concepts regarding the specimen geometry and classical theories regarding the size effect, and ultimately jeopardise the transferability of conventional tensile test standards to FFF parts. Finally, the statistical analysis of the tensile properties of poly(lactic acid) (PLA) FFF specimens printed according to different standards (ASTM D638 type I and ASTM D3039) and in different sizes provides experimental evidence to confirm the literature-based argumentation. Ultimately, the literature survey, supported by the experimental results, demonstrates that, until dedicated standards become available, existing standards for tensile testing should be applied to FFF with prudence. Whilst not specified in conventional standards, set-up and printing parameters should be fully reported to ensure the repeatability of the results, rectangular geometries should be preferred to dumbbell-like ones in order to avoid premature failure at the fillets, and the size of the specimens should not be changed arbitrarily.