Development of a smart farming tool to monitor the degree of dew retting of flax stems

Flax fibres are a natural, sustainable product which have applications ranging from textiles to composite materials. A process known as 'retting' is required to facilitate the mechanical extraction of flax fibres from their associated stems. The goal of retting is to break down the binding material (pectin) holding the fibre bundles to the core and epidermis of the stem, not the pectin which holds the single fibres together which form long, practical 'technical' fibres. For natural dew retting, there is therefore an optimum retting period: insufficient retting renders fibre extraction difficult and leads to low yield, whereas excessive retting can lead to poor technical fibre quality. For centuries, the timing of the retting termination has been evaluated by artisanal means. Today, modern technology enables one to envisage tools that indicate optimal retting. Here, we demonstrate the development of a smart tool combining mechanics, digital microscopy, and image analysis. The cracking of the outer tissue of the flax stems, due to mechanical torsion applied to the stems by the tool, is quantified using optical microscopy and image analysis, and is demonstrated to serve as an observable indicator of the degree of retting of the stems.