Im Gegen­satz zu klassi­schen Materia­lien hängen die Eigen­schaf­ten von Metama­te­ria­lien von deren spezi­el­ler Mikro­struk­tur ab. Neue Herstel­lungs­ver­fah­ren erlau­ben die Erzeu­gung von 3D-Metama­te­ria­lien mit Mikro­struk­tu­ren auf der Mikro­me­ter-Ebene. In diesem Projekt ging es darum, das Design von neuen mecha­ni­schen Metama­te­ria­lien zu erforschen.

Betei­ligt waren die Hector Fellows Peter Gumbsch und Martin Wegener gemein­sam mit dem HFA Postdok­to­ran­den Dr. Muamer Kadic (Karls­ru­her Insti­tut für Techno­lo­gie, Insti­tut für Angewandte Physik) und dem HFA Dokto­rand Claudio Findei­sen (Karls­ru­her Insti­tut für Techno­lo­gie, Insti­tut für Angewandte Materialien).

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).