YIN Grants stimulate follow-up research

Enhanced printing procedure for controlled growth of carbon nano fibres on a substrate

The annual YIN Grants are meant as a targeted measure to enable a YIN member (or even better an interdisciplinary team of YIN members and/or alumni) to pursue an innovative scientific idea. Ideally, first research funded by the YIN Grant becomes a seed for longer-standing collaborations and bigger follow-up projects. Here we show an example for how the impulse set by a small YIN Grant can lead to nice results years later.

The story starts more than 3 years ago, when in 2015 Julia Syurik and Michael Hirtz won a YIN Grant for their proposal “Towards Massively Parallelized Electrochemical Dip-Pen Nanolithography”
(YIN Insight 2015/2016). In general, in electrochemical dip-pen nanolithography (DPN), an electric field is applied to the sharp tip of an atomic force microscope. This setup is used in conjunction with metal salts to deposit highly localized metal nanostructures. Aim of the initial YIN Grant was to demonstrate, that this technique can be parallelized by using arrays of tips with the prospect of speeding up the process of structure generation. The YIN Grant allowed us to hire a student assistant and some needed materials to modify our existing DPN setup with a custom-made holder for parallelized writing.

However, our joint story did not stop there! Initially just being an elusive afterthought, we used the protocols for the deposition of nickel salts, a byproduct of the initial project, to tackle a different problem: how to grow carbon nano fibers (CNF) in a controlled way and at controlled positions on a substrate, e.g. an electronic device or an electrode? The difficulty lies in the precise positioning of CNFs which
involves rather expensive and slow techniques (such as E-beam lithography), making fabrication of big CNF-arrays nearly impossible in a feasible time.

A PhD student supervised by Julia Syurik found the perfect solution in the deposition processes initially developed during the YIN Grant. Based on these results, we optimized the printing procedures for the nickel salt that now acts as a catalytic center for the growth of CNFs in a facile open flame procedure. Interestingly, a new type of CNF morphology in form of Λ and λ shapes could be observed for which a growth model was developed. By tuning the size of the spotted metal salt catalyst features, we could obtain control down to the point where only single CNFs grow at the specific deposition points. The details of the printing and growth process are topic of the student’s PhD thesis and a publication in the research journal Small1. Our findings beckon for future projects to exploit the procedure for tailored deposition of CNFs on functional devices. Thus, the initial YIN Grant stimulated a long-standing collaboration between our groups that is still far from over.