Review: Beyond the cavity walls — a non-invasive acoustic–vibration framework for early detection of microwave boil-over spillage

Microwave ovens are widely used for cooking food and heating liquids; however, excessive heating of liquids often leads to rapid boiling and boil-over spillage, contamination of the cavity, arcing, and potential burn injuries. Despite the availability of built-in sensing technologies in modern microwave ovens, these systems are primarily designed for general cooking control and do not reliably prevent liquid boil-over. This paper presents a comprehensive review of existing approaches to spillage prevention, including internal sensor technologies, physical barriers, behavioral interventions, and timer-based control methods, highlighting their key limitations in addressing real-time boil-over detection. The paper further reviews advances in acoustic emission and vibration-based boiling detection in related thermal systems, such as stove-tops, induction cook-tops, and industrial processes, where these methods have demonstrated high reliability in identifying boiling regimes. Based on these insights, this study proposes a conceptual non-invasive, externally mounted sensing framework specifically tailored for domestic microwave ovens. The proposed system utilizes low-cost micro-electro-mechanical systems (MEMS) accelerometers and microphones to capture vibration and acoustic signatures from the outer casing of the microwave, combined with a threshold-based signal processing algorithm for early detection of boiling activity. The feasibility of transferring these sensing principles is supported by the established effectiveness of acoustic and vibration sensing in other heating environments. The framework offers a low-cost, universal, and retrofit-compatible solution for early spillage detection without requiring internal modification of the appliance. The proposed framework is presented as a low-cost, universal, and retrofit-compatible research outlook. Experimental validation and performance evaluation under realistic operating conditions are identified as the subject of planned follow-up work.