The postdoc Dr. Muamer Kadic and the doctoral student Claudio Findeisen, both from the Karlsruhe Insti­tute of Technol­ogy, work together in this project of the Hector Fellows Peter Gumbsch and Martin Wegener. They inves­ti­gate the proper­ties of novel metamaterials.

In contrast to classic materi­als, the proper­ties of metama­te­ri­als result from their specific microstruc­ture rather than their atomistic proper­ties. New produc­tion methods, such as direct laser writing, allow for the produc­tion of such 3D metama­te­ri­als with microstruc­tures in the range of microm­e­ters, which is impos­si­ble with standard fabri­ca­tion methods. In this collab­o­ra­tion project, the young scien­tists inves­ti­gate the design of new classes of metama­te­ri­als. They present two classes of materi­als to protect from linear vibra­tions using cloak­ing devices and to absorb energy via inner insta­bil­i­ties of micro-lattices.

An elasto-mechan­i­cal “unfee­la­bil­ity” cloak made of penta­mode metamaterials

Metama­te­r­ial-based cloaks make objects that differ from their surround­ings appear just like their surround­ings. To date, cloak­ing has been demon­strated exper­i­men­tally in many fields of research. However, cloak­ing in the appar­ently simple case of three-dimen­sional solid mechan­ics is more demand­ing.
Inspired by invis­i­ble core-shell nanopar­ti­cles in optics, the scien­tists design an approx­i­mate elasto-mechan­i­cal core-shell “unfee­la­bil­ity” cloak based on penta­mode metama­te­ri­als (see Figure 1). The result­ing three-dimen­sional polymer microstruc­tures with macro­scopic overall volume are fabri­cated by rapid dip-in direct laser writing optical litho­g­ra­phy. The researchers perform quasi-static exper­i­ments and map the displace­ment fields by autocor­re­la­tion-based analy­sis of recorded movies.

Tailored buckling micro-lattices as reusable light-weight shock absorbers

Struc­tures and materi­als absorb­ing mechan­i­cal (shock) energy commonly exploit either viscoelas­tic­ity or destruc­tive modifi­ca­tions. Based on a class of uniax­ial light-weight geomet­ri­cally nonlin­ear mechan­i­cal micro-lattices and using buckling of inner elements, they achieve either a sequence of snap-ins followed by irreversible hysteretic – yet repeat­able – self recov­ery or, alter­na­tively, multi-stabil­ity enabling program­ma­ble behav­ior. Proof-of-princi­ple exper­i­ments on three-dimen­sional polymer micro-struc­tures are done (see Figure 2).