Recent Advances in 4D-Printed Bioelectronics: Materials, Structural Design, Fabrication, and Applications.

Bioelectronics are pivotal to biomedical engineering as they enable seamless communication between electronic devices and living tissues. However, conventional interfaces with static, rigid configurations often suffer from mechanical mismatch, chronic inflammation, and progressive signal degradation. By integrating stimuli-responsive materials with programmable architectures, 4D-printed devices enable in situ shape transformation and modulus adaptation, establishing a new paradigm for adaptive, high-fidelity biointerfaces. This review systematically examines recent advancements in 4D-printed bioelectronics. We first evaluate how smart materials-including hydrogels, liquid crystal elastomers (LCEs), and shape memory polymers (SMPs)-synergize with structural concepts such as auxetic lattices and kirigami/origami geometries to achieve dynamic compliance. Subsequently, we list advanced additive manufacturing strategies, particularly vat photopolymerization and direct ink writing (DIW) as well as hybrid printing strategies, which ensure high-precision fabrication. Furthermore, we highlight transformative biomedical applications, including neural interfaces, wearable devices, soft robotics, and implantable therapeutic devices. Finally, we discuss future directions for 4D-printed bioelectronic devices, focusing on the long-term stability of bioelectronic signal transduction, the integration of multifunctionality, bidirectional bioelectronic modulation, manufacturing scalability and standardization, and artificial intelligence (AI)-driven design and predictive modeling.