Scoby

Tensioni Molecolari

Tensioni Molecolari, a project by Francesca Zeccara, explores the possibilities of Growing Materials (GW) within established markets, aiming to advance research towards the use of Regenerative Materials for a more circular design and industry. Focusing on Bacterial Cellulose (BC), the project consists of two main phases: the first phase involves optimising resources for fermentation to minimise material waste. The second phase of experimentation focuses on the material's potential within the upholstered furniture market, examining the possibilities of combining BC with other natural materials.

In the first phase, the most influential parameters during fermentation were identified, including ingredients used for the medium, pH, brix, medium quantity, and fermentation temperature. These parameters were analysed day by day over ten fermentation cycles and then systematised to understand which values were optimal for achieving a short cycle time, high-quality film, and reduced medium waste.

During the second phase of experimentation, BC was combined with six previously identified natural materials: cotton, jute, hemp, coconut fibres, wool, and natural latex foam. These six materials were coupled with Bacterial Cellulose using two methodologies: in situ - involving direct insertion during fermentation - and ex situ - which occurs after BC fermentation through a manual assembly step between padding and BC films. Due to the difficulty of maintaining natural fibres for an extended period within the sugary fermentation medium, the ex situ methodology was identified as promising. To understand the real mechanical properties of the resulting ex situ couplings, the obtained samples underwent mechanical resistance tests to assess their performance. They were subjected to a maximum weight of 25 kg and subsequently analysed to understand which combination showed good resistance and elastic return. Among all, the sample consisting of two BC films and internal padding made of natural latex foam proved suitable for upholstery, as the elasticity of the latex complements the limited elasticity of BC, preventing permanent deformation. Additionally, given the limited aesthetic performance of industrial natural latex upholstery, a layer of wool was chosen to be integrated into the final padding.

For the final prototype, padding consisting of two layers of BC with natural latex foam padding and two films of handcrafted raw wool was assembled. Manual assembly took place before the complete drying of BC, utilising its self-welding capabilities to permanently enclose the padding. Following this step, the completion of the drying process for the padding occurred inside a wooden drum, to maintain tension on the component in question, creating the seating surface of the stool.

For the structure, it was decided to place the tensioned padding on a wooden seating surface, made flexible using the kerfing technique thanks to CNC milling. This design choice highlighted the semi-structural properties of the coupled BC, ensuring a resistance of 100 kg. The entire stool is also made of natural materials - birchwood - and designed according to the principles of Design for Disassembly, eliminating the use of permanent joints.

Tensioni Molecolari thus represents the possibility of integrating GMs into semi-industrial production, reducing production waste and optimising processes to reduce their environmental impact.

Making process

The experimentation phases integrate the Material Driven Design methodology with the Do It Yourself approach to obtain practical evidence and a design process aimed at identifying a promising market for BC.

For the first phase of fermentation optimisation, two promising recipes were tested: one involving the mixture of coconut water and Scoby mother, and the other using green tea and Scoby mother. For each of these recipes, three different quantities of medium - 100, 200, and 400 ml - were fermented to assess differences in fermentation duration, production waste, and output quality. This cycle was repeated ten times to identify consistent fermentation behaviour, showing how the recipe that includes the use of green tea and Scoby mother leads to superior aesthetic properties, a reduced cycle time, and minimised waste in post-fermentation. Once the optimal parameters were defined, they were applied to the subsequent phases of the experimentation, namely the production of padded samples of BC and natural fibres, such as cotton, jute, hemp, coconut fibres, wool, and natural latex foam.

For the experimentation related to in situ coupling, the paddings were inserted into a tank following the fermentation of BC film and kept inside the tank for approximately 10 days, in order to allow for the formation of a layer of BC below and above the inserted padding. It was observed that the padding, upon drying, became thinner due to prolonged contact with the sugary liquid.

For the production of samples obtained through ex situ assembly, the padding was inserted into two BC films during the drying phase, exploiting the regenerative material's ability to self-weld when still wet. Despite this methodology involving an additional manual step and thus a longer process, the result proved to be highly performing both in terms of mechanical and aesthetic performance. Even the stress test, conducted using the Do It Yourself approach with the use of gym weights, demonstrated the mechanical superiority of ex situ samples, particularly the sample made with natural latex foam.

For the construction of the wooden structure, the CNC milling process was used to achieve high cutting precision and the ability to make the seating surface flexible using the kerfing technique. The dialogue between industrial and innovative production processes, such as fermentation, the resources optimisation, and the use of natural materials, represents an emerging opportunity for design and designers to create a dialogue between industrialisation and sustainability, through a reevaluation of the use of materials and their regenerative time.

Text submitted by the maker and edited by the Future Materials Bank. For information about reproducing (a part of) this text, please contact the maker.