Nonlinear targeted energy transfer: state of the art and new perspectives

Following a brief review of current progress in the field of nonlinear targeted energy transfer (TET), we discuss some general ideas and methods in this field and describe certain possible future venues for further developments; these go beyond the current paradigm of implementing TET by means of nonlinear energy sinks. Four such emerging research fields are discussed, namely (i) the new and promising concept of intermodal targeted energy transfer, (ii) the implementation of TET in nonlinear acoustic metamaterials, (iii) the break of classical reciprocity in elastodynamics in the context of TET, and (iv) the role of TET on the bandwidth of general classes of nonlinear resonators. Our aim is to describe the main ideas, summarize recent developments, outline possible directions for future work, and possibly trigger further research in the discussed topics and also in other possible TET-related topics not discussed herein.