Low-Heat and Near-Silent Pneumatic Source Driven by Integrated Endothermic–Exothermic Chemical Reactions for Soft Robots

Among various soft actuators, soft pneumatic actuators (SPAs) powered by pressurized gases have been widely adopted due to their structural simplicity, ease of fabrication, and ability to generate diverse and adaptable motions. However, conventional mechanical compressors and chemical reaction-based pneumatic sources that supply pressurized gas to these actuators often generate substantial acoustic noise and heat, limiting their practical use. In this study, we propose an electronics-free, near-silent, and low-heat pneumatic source that integrates endothermic-exothermic chemical reactions to balance heat generation while producing pressurized gas. By only using passive mechanical components that autonomously regulate the reaction process, the pneumatic source achieved a steady output pressure of 7 bar and a flow rate of 6 liters per minute through the chemical reactions between phosphoric acid and cesium bicarbonate. The proposed pneumatic source operated with minimal temperature rise (maximum 36°C) and low acoustic noise of 40 dBA, comparable to the ambient noise of a quiet residential environment. The proposed approach demonstrates an enthalpy-balanced acid-bicarbonate system for combining endothermic and exothermic reactions to achieve thermally balanced and noise-suppressed pneumatic operation. Therefore, the proposed concept can serve as a practical and versatile pneumatic source for driving a wide range of SPAs.