EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

In the last decades, mobile miniaturized devices have attracted an increasing interest due to their great potential in a broad range of applications. Untethered microrobots would allow less invasive surgery, precise cell manipulation and efficient drug delivery [1]. In this context, artificial bacterial flagella (ABF) are highly attractive due to their precise magnetic control. One of the most interesting techniques for their production is direct laser writing (DLW) [2], which permits the reproducible fabrication of polymeric microdevices. Following DLW, metallic layers are normally sputtered on the devices [3] to allow magnetic manipulation.

In an attempt to overcome the intrinsic limitations of sputtering (shadowing effect, high cost and limited obtainable magnetic properties), we investigated for the first time the possibility to apply functional coatings on DLW printed polymeric ABFs via wet metallization. This approach is costless and able to yield conformal metallic layers with tunable hard magnetic properties [4]. Moreover, wet metallization can be exploited to deposit composites that combine two or more functionalities in the same layer [5].

The wet metallization of micrometric delicate objects like ABFs presents significant challenges and it must be carefully investigated. Consequently, we initially fabricated micrometric ABFs using DLW and we subsequently conformally deposited a semi-hard magnetic alloy (CoNiP) on them via room temperature metallization. The morphology and the swimming behavior of the devices obtained were characterized. We also demonstrated the possibility to introduce multiple functionalities on the ABFs by depositing a silver layer via Tollens’ reaction. In this way, we were able to implement a bacteria killing functionality.

[1] Chen et al., DOI: 10.1002/adma.201705061

[2] Li et al., DOI: 10.1039/D0CS01062F

[3] Kim et al., DOI: 10.1038/srep30713

[4] Bernasconi et al., DOI: 10.1039/C8MH00206A

[5] Bernasconi et al., DOI: 10.1016/j.addma.2019.04.022