Today's electronic products are moving toward personal, portable, and flexible electronics with the integration of multifunctional sensors and self-powering technologies. Consequently, efficient and highperformance mechanical−electronic interfaces will be heavily considered in the development of future electronics. Piezotronic materials are active components for the conversion of mechanical stimuli to electrical signals and vice versa. In particular, low-dimensional (LD) materials offer greater efficiencies in piezoelectric materials than their bulk counterparts. Piezoelectric LD materials have attracted significant attention because of their successful integration in miniatured and flexible electronics. The origin of the piezoelectric responses of the LD materials is ascribed as a loss of centrosymmetry and inversion center. However, challenges exist in utilizing piezoelectric materials to their full potential, including effective charge separation upon external stimuli and imperfections in their crystal structures. Therefore, considerable efforts have been devoted to engineering the LD piezoelectric materials by rational structural design and chemical modification to further improve the piezoelectric performances. Herein, we comprehensively review the recent advances for engineering technologies of piezoelectric materials on the scale of zero-dimensional (0D), one-dimensional (1D), and two-dimensional (2D), which are mainly focused on creating defects, doping, and forming Janus structures and heterointerfaces with other materials. Meanwhile, the relationships between the morphological, physicochemical, and electronics of engineered LD piezoelectric materials and their piezoelectric performances are systematically discussed. Finally, we further present the prospect and challenge of the field and future research direction, aiming to inspire more research for achieving high-performance LD piezoelectric materials in sensors, actuators, and micro-and nanoelectromechanical systems.

The synthesis of bi-and tetra-functional tri-aryl ether epoxy resin isomers and their subsequent cure with 44 diamino diphenyl sulphone (DDS) is presented here. The effect of varying aromatic substitution and cross-link density on the structure, property, and processing relationships is explored for 1,3 bis (3-glycidyloxyphenoxy)benzene (133 BGOPB), 1,4 bis(4-glycidyloxyphenoxy) benzene (144 BGOPB), N,N,N,N-tetraglycidyl 1,3-bis (3-aminophenoxy) benzene (133 TGAPB), and N,N,N,N-tetraglycidyl 1,4-bis (4-aminophenoxy) benzene (144 TGAPB). Meta substitution to the aromatic ring reduces the rate of reaction, glass transition temperature, yield strain and crosslink density, coefficient of thermal expansion, and side reactions, while increasing strain softening, compressive modulus and strength, and methyl ethyl ketone ingress. Increasing crosslink density increases the glass transition temperature, promotes side reactions during cure, and increases compressive modulus, strength, and yield strain, while reducing coefficients of thermal expansion, methyl ethyl ketone ingress, and density. The results are discussed in terms of packing efficiency of the meta-substituted epoxy resins and the role of short range molecular mobility caused by the lack of an aromatic axis of rotation. K E Y W O R D Sisomerism, network properties, reaction kinetics, synthesis