Sustainable Fabrication of Biodegradable Soft Robotic Actuators

This paper investigates starch-based rice paper as a sustainable, biodegradable, and widely available alternative to elastomers for soft robotics. Starch-based materials can address the environmental issues of traditional, non-degradable materials like silicone, offering a significant reduction in production energy and waste. Rice paper is sustainably sourced from rice (Oryza sativa L.) and cassava root (Manihot esculenta) and we show that it offers a biodegradable, water-soluble, non-toxic, and low-cost solution with mechanical properties suitable for soft robotics. Young's Modulus at stretch ≤2 and Shore Hardness were found to be 52.8 kPa and Shore 00 32.33 respectively, which are comparable to Ecoflex™ 00-30. A general process for soft robotic fabrication using rice paper is presented, including the rapid fabrication and characterization of a pneumatic linear actuator demonstrator. The actuator generated an extension strain up to 83.9% at a pneumatic pressure of 4.7 kPa. Experimental investigations into end-of-life disposal showed that rice paper fully biodegrades on soil within 32 days and fully dissolves in 20 °C water within 18 days. Finally, the potential for a circular life cycle was demonstrated by using the linear actuator as a growing medium with plant seeds laminated between its layers. The seeds successfully germinated with root and plant growth through the actuator. The accessibility and renewable nature of these materials make them suitable for sustainable practices in soft robotics.