The proliferation of wearable healthcare devices has revolutionized personal health monitoring and management, enabling continuous monitoring of physical and biochemical signs such as heart rate and blood glucose levels. This review discusses the fabrication methods and applications of flexible wearable healthcare devices, focusing on materials like polymers, liquid metals, composites, biodegradable materials, and self-healing materials. These devices offer insights into human health, allowing for proactive rather than reactive healthcare approaches. The review highlights the challenges and future prospects in the field, emphasizing the importance of biocompatibility, flexibility, and durability. Key applications include real-time monitoring, in vitro diagnosis, body composition analysis, and energy harvesting. The review also details the development of various types of biosensors, including physical and chemical sensors, and their integration into wearable devices. Additionally, it explores the use of biodegradable and self-healing materials to enhance the sustainability and reliability of wearable healthcare devices. Finally, the review discusses the significant milestones in the development of wearable sensors, from first-generation devices based on physical mechanisms to second-generation devices that use biofluids for non-invasive monitoring.The proliferation of wearable healthcare devices has revolutionized personal health monitoring and management, enabling continuous monitoring of physical and biochemical signs such as heart rate and blood glucose levels. This review discusses the fabrication methods and applications of flexible wearable healthcare devices, focusing on materials like polymers, liquid metals, composites, biodegradable materials, and self-healing materials. These devices offer insights into human health, allowing for proactive rather than reactive healthcare approaches. The review highlights the challenges and future prospects in the field, emphasizing the importance of biocompatibility, flexibility, and durability. Key applications include real-time monitoring, in vitro diagnosis, body composition analysis, and energy harvesting. The review also details the development of various types of biosensors, including physical and chemical sensors, and their integration into wearable devices. Additionally, it explores the use of biodegradable and self-healing materials to enhance the sustainability and reliability of wearable healthcare devices. Finally, the review discusses the significant milestones in the development of wearable sensors, from first-generation devices based on physical mechanisms to second-generation devices that use biofluids for non-invasive monitoring.