Flexible electronics represent a transformative advancement in technology, emerging from the need for more adaptable and versatile electronic systems. Initially driven by the limitations of traditional rigid electronics, this field leverages materials like organic semiconductors, conductive polymers, and thin-film technologies to create devices that can bend, stretch, and conform to various surfaces. Originating in the early 2000s, flexible electronics have found applications in wearables, flexible displays, and smart textiles. Innovations in fabrication techniques, such as roll-to-roll processing and printed electronics, have accelerated their development, promising new possibilities for portable technology and interactive surfaces in consumer electronics, healthcare, and human machine interfaces. Our research interests focus on developing skin-integrated, close-loop human machine interfaces, covering motion caption system, control panel, manipulated robots, powering management system, and human sensations feedback system (haptics, olfaction, and gustation). The flexible human machine interfaces have exhibited their advances in various application fields, ranging from healthcare monitoring, to clinical treatment, to remote surgery, to education, and to VR/AR/MR.