Interwoven refers to material structures made by growing plant roots into man-made patterns. Originally developed as an art piece to demonstrate root intelligence and bring attention to human-nature relations, Interwoven shows the potential to disrupt various commercial industries, especially as textile-based natural fiber reinforcements for composite materials. The artist that created Interwoven, Amsterdam-based Diana Scherer, started a collaboration with the TU Delft Faculty of Industrial Design Engineering to help further develop Interwoven from an art piece to a sustainable material for products design. Following the Material Driven Design method (Karana, et al., 2015), two students have identified materials experience opportunities created by Interwoven materials, the mechanical properties and internal structure of Interwoven are still not fully understood.

This study tackles the challenge of performing a technical characterization on Interwoven structures in an effort to correlate processing parameters to its structure, properties, and performance. It is known from past works that Interwoven is fragile and “weak”, but a quantified value for these terms serves as a point of comparison with other materials in the market. To determine these values, a series of tensile tests were performed on grids with a simple square pattern. Dynamic Mechanical Analysis (DMA) tests performed on single roots proved that the amalgamation of roots that make up an Interwoven structure do not efficiently transfer tensile loads since the tensile strength and elastic moduli of Interwoven samples were nearly two orders of magnitude lower than those of a single root. Load transfer between roots was improved through the design of natural fiber-reinforced composites (NFRCs). The (bio)-polymer matrix used for these NFRCs was made up of agar gel, which improved the tensile properties of Interwoven samples, but was still lower than the single root.

A full characterization of a material correlates the observed properties to the structure of the material, which is done through the use of microscopy. Microscopic analyses were performed on all the tested samples to find any correlation between the observed tensile properties and the structure of Interwoven samples. In addition to providing insight about the complex interactions of roots as they form the patterns that they grow into, the microscopy also revealed that there is a direct correlation between the number of root tips (root endings) present at the intersection of squares in the grid and the mechanical properties of the sample.

With further research, this result can be tied to a parameter that the designer has direct control of, giving them better control of the properties of their Interwoven structures. Varying cell size in square patterns also allows designers to create structures with locally varying properties. The correlations between design parameters and material strength are summarized in the Guidelines to Designing with Interwoven booklet. A material demonstrator was also designed to showcase the locally variable mechanical properties in one structure while summarizing the test results in a way that is accessible and easy to understand.