Assembly and applications of 3D conformal electronics on curvilinear surfaces

3D conformal electronics represent the next-generation microelectronics that exhibit similar electrical functions as conventional, planar ones, but can be prepared on arbitrary curvilinear surfaces for innovative applications. Nevertheless, established planar microfabrication techniques are no longer satisfactory for such electronic systems, and this increases the demand for brand new structural designs and functional materials. Recent impressive technical advances have overcome many of the historical drawbacks of 2D planar electronics when they were integrated onto rigid, deformable, and time-dynamic curvilinear surfaces, including the most broadly recognized transfer printing and unique options for conformal electronics like laser structuring, inkjet printing, and holographic lithography. Herein, we review the key developments in conformal electronics technology and highlight their potential value, covering both the state-of-the-art devices and requirements for conformal attachments. We begin with the conformal design from the perspective of key mechanics and materials and then expand to the latest progresses and future prospects of 3D soft and holographic lithography, laser direct structuring, and digital inkjet printing on curvilinear surfaces. Then, we highlight 3D conformal electronics through active/passive self-assembly. Finally, the challenges and opportunities facing conformal electronics are discussed, from personalized healthcare, artificial implants, and wearable electronics to aerospace.