3D piezoelectric microsystems pop up

摘要

Piezoelectric transduction has been usedto build devices for energy harvesting,sensing and actuation, with applicationsin areas such as the automotive industry1and biomedicine2,3. Recently, there has beengrowing interest in piezoelectric devicesfor self-powered and wearable systemsthat can detect or harvest broadband, lowfrequencymechanical stimuli includingambient vibrations or human motion.Piezoelectric microsystems are typicallyfabricated using thin film processes, yieldingdevices with 2D configurations. Yet, suchplanar devices are typically tailored towardnarrow-band, high-frequency applicationsor limited degrees of freedom in a 2Ddesign space. Transforming conventional2D structures into 3D could allow accessto a greater diversity of operating modes.Writing in Nature Electronics, YihuiZhang, Yonggang Huang, John Rogers andcolleagues8 demonstrate the fabricationof 3D piezoelectric microsystems via thecompressive buckling of lithographicallydefined 2D patterns. The 3D piezoelectricmicrosystems offer new functionalities andimproved device performance comparedwith their 2D counterparts8.The researchers — who are basedat Northwestern University, TianjinUniversity, University of Missouri,Shanghai Jiaotong University and TsinghuaUniversity — developed a fabricationscheme to create various 3D piezoelectricmesostructures with tailored geometriesand mechanical attributes. The structurescomprise a layer of piezoelectric polymer(polyvinylidene difluoride) sandwichedbetween two metallic electrodes. Thefabrication scheme generally followsthree main steps: 2D precursor designsare defined using planar microfabricationstrategies; the structures with selectedbonding sites are transfer printed ontoa pre-strained elastomeric substrate;and the strain is released, such that the2D geometry reversibly transforms viabuckling to a 3D microsystem.