Recent Advances in Flexible and Wearable Pressure Sensors Based on Piezoresistive 3D Monolithic Conductive Sponges. 
High-performance flexible strain and pressure sensors are important components of the systems for human motion detection, human-machine interaction, soft robotics, electronic skin, etc.,  which are envisioned as the key technologies for applications in future human healthcare monitoring and artificial intelligence.  In recent years, highly flexible and wearable strain/pressure sensors have been developed based on various materials/structures and transduction mechanisms.  Piezoresistive three-dimensional (3D) monolithic conductive sponge, the resistance of which changes upon external pressure or stimuli, has emerged as a forefront material for flexible and wearable pressure sensor due to its excellent sensor performance, facile fabrication, and simple circuit integration.  This review focuses on the rapid development of the piezoresistive pressure sensors based on 3D conductive sponges.  Various piezoresistive conductive sponges are categorized into four different types and their material and structural characteristics are summarized.  Methods for preparation of the 3D conductive sponges are reviewed, followed by examples of device performance and selected applications.  The review concludes with a critical reflection of the current status and challenges.  Prospects of the 3D conductive sponge for flexible and wearable pressure sensor are discussed.