Analytical expressions for the bi- and tri-stable conditions of a multi-stable energy harvester (MEH) are derived on the basis of bifurcation analyses, and the associated multi-stable regions are characterized in a 2-D parametric space. It is found that a special boundary condition exists for a triple-well with a uniform depth (T_U boundary condition), originating from a degenerate pitchfork bifurcation (DPF) point. Interestingly, the outermost well-to-well distance of the triple-well potential, when subjected to the condition that the maximum well depth is kept constant, becomes widest when the well depth is uniform. Accordingly, instead of investigating all possible parametric conditions, the design parameters for the optimal well configuration of the MEH can be sought most efficiently by simply tracing them on the T_U boundary. A detailed examination of the potential well configurations along the T_U boundary reveals that the most efficient energy harvesting from low-intensity ambient vibrations can be achieved on a T_U boundary point, near the DPF point but inevitably a certain distance apart, by inducing an enlarged interwell motion. This investigation is experimentally validated.

In this study, a three‐dimensional printing technique is applied for the fabrication of novel functionally graded magnetic shape memory polymers (SMPs) to create high‐resolution multimaterial shape memory architectures. This approach is applied to a copolymer network of photocurable methacrylate using high projection stereolithography. Carbonyl iron particles (CIPs) were physically embedded in a polymer matrix to add magnetic functions to the SMPs. The glass transition characteristics and shape memory effect were also investigated by varying the composition of the SMP. The microstructured, lightweight SMPs showed interesting shape memory behaviors, as observed in hot environment. The almost perfect strain recovery rate of poly(ethylene glycol) dimethacrylate was measured (99.95% using a tension set bar). The results of dynamic mechanical analysis and thermogravimetric analysis reveal an increment in the thermal conductivity after embedding the CIPs. Further, the results of dynamic mechanical analysis, differential scanning calorimetry, and scanning electron microscopy reveal close interaction between the particles and matrix. X‐ray diffraction was used to characterize the iron particles and polymer structure. These results, along with the electrical and magnetic tests, strongly support the remote controllability of the material properties of the present functionally graded magnetic SMPs for a broad range of temperature and/or magnetically responsive material applications by using eddy current heating and/or magnetorheological polymeric effects. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45997.