Designing the Persistence Length of Digital Magnetic Polymers*

Magnetic handshake materials [1] are new self-assembling platforms that use magnetic dipole patterns to create lock and key interactions between building blocks to guide assembly. Because the technology is scale invariant, building blocks can range in size from centimeters to microns. Here, we show this platform can be used to design the persistence length of digital magnetic polymers. Specifically, we use a shaker to agitate chains of millimeter sized panels, each containing a 2x2 square array of magnets. By changing the contact surfaces between panels from flat to hemispherical the persistence length changes from ~10^4 to ~10^2 panel lengths for the same shaking settings (amp & freq). Similarly, keeping a hemispherical contact but changing the dipole pattern again results in a 2 order of magnitude change in persistence length. Combining the approaches enable us to change the persistence length by almost 4 orders of magnitude. This system constitutes a new type of self-healing granular polymer, which in addition to modeling molecular polymeric analogues may find uses in its own right. Finally, I will describe our fabrication efforts to make the panels microns in size where fluctuations in such polymers would be thermal.

References:
[1] Niu, et al. PNAS, 116 (2019)