Advances in Biointegrated Wearable and Implantable Optoelectronic Devices for Cardiac Healthcare Biointegrated wearable and implantable optoelectronic devices are crucial for cardiac healthcare, offering seamless integration with the human body for continuous, real-time monitoring and treatment. These devices are designed to be flexible and stretchable, enabling them to conform to dynamic organs like the heart, skin, and brain. The review discusses recent advancements in the design, application, and challenges of these devices. The article highlights the importance of mechanical design, interface adhesion, and encapsulation strategies in achieving biointegrated optoelectronic devices. Flexible and stretchable optoelectronic devices are essential for monitoring cardiac physiological parameters such as blood oxygen saturation (SpO2), heart rate (HR), and blood pressure (BP). These devices can be worn on the skin or implanted in the body, providing continuous monitoring without spatial or temporal constraints. In addition to monitoring, these devices are also used for therapeutic applications, such as cardiac optogenetics and non-genetic stimulation. Optogenetics allows for precise control of cardiac rhythm with low energy consumption and painless defibrillation. Non-genetic stimulation systems use photoelectric conversion to enable light-controlled electrical stimulation without the need for complex genetic engineering. The review also discusses the design of biointegrated optoelectronic devices, including structural engineering and intrinsic stretchable materials. Structural engineering involves creating buckling, island-bridge, and kirigami structures to enhance flexibility and stretchability. Intrinsic stretchable materials are designed to have inherent flexibility and durability, allowing for high strain and integration with dynamic tissues. Interface adhesion is crucial for ensuring stable contact between the devices and biological tissues. The review presents various adhesion strategies, including irreversible covalent adhesion, dynamic covalent adhesion, and noncovalent adhesion. These strategies ensure strong and reversible adhesion, enabling the devices to maintain functionality in dynamic environments. Encapsulation design is essential for protecting the electronic components of implantable devices from biofluid erosion. The review discusses long-term and biodegradable encapsulation strategies, including soft polymers, inorganic materials, and alternating organic-inorganic layers. These encapsulation strategies ensure the devices remain functional for extended periods or degrade safely after their operational lifespan. The applications of biointegrated optoelectronic devices in cardiac healthcare are extensive, ranging from continuous monitoring of physiological parameters to precise therapeutic interventions. These devices offer a promising solution for improving the diagnosis and treatment of cardiovascular diseases, enabling personalized and intelligent healthcare.Advances in Biointegrated Wearable and Implantable Optoelectronic Devices for Cardiac Healthcare Biointegrated wearable and implantable optoelectronic devices are crucial for cardiac healthcare, offering seamless integration with the human body for continuous, real-time monitoring and treatment. These devices are designed to be flexible and stretchable, enabling them to conform to dynamic organs like the heart, skin, and brain. The review discusses recent advancements in the design, application, and challenges of these devices. The article highlights the importance of mechanical design, interface adhesion, and encapsulation strategies in achieving biointegrated optoelectronic devices. Flexible and stretchable optoelectronic devices are essential for monitoring cardiac physiological parameters such as blood oxygen saturation (SpO2), heart rate (HR), and blood pressure (BP). These devices can be worn on the skin or implanted in the body, providing continuous monitoring without spatial or temporal constraints. In addition to monitoring, these devices are also used for therapeutic applications, such as cardiac optogenetics and non-genetic stimulation. Optogenetics allows for precise control of cardiac rhythm with low energy consumption and painless defibrillation. Non-genetic stimulation systems use photoelectric conversion to enable light-controlled electrical stimulation without the need for complex genetic engineering. The review also discusses the design of biointegrated optoelectronic devices, including structural engineering and intrinsic stretchable materials. Structural engineering involves creating buckling, island-bridge, and kirigami structures to enhance flexibility and stretchability. Intrinsic stretchable materials are designed to have inherent flexibility and durability, allowing for high strain and integration with dynamic tissues. Interface adhesion is crucial for ensuring stable contact between the devices and biological tissues. The review presents various adhesion strategies, including irreversible covalent adhesion, dynamic covalent adhesion, and noncovalent adhesion. These strategies ensure strong and reversible adhesion, enabling the devices to maintain functionality in dynamic environments. Encapsulation design is essential for protecting the electronic components of implantable devices from biofluid erosion. The review discusses long-term and biodegradable encapsulation strategies, including soft polymers, inorganic materials, and alternating organic-inorganic layers. These encapsulation strategies ensure the devices remain functional for extended periods or degrade safely after their operational lifespan. The applications of biointegrated optoelectronic devices in cardiac healthcare are extensive, ranging from continuous monitoring of physiological parameters to precise therapeutic interventions. These devices offer a promising solution for improving the diagnosis and treatment of cardiovascular diseases, enabling personalized and intelligent healthcare.