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Actuation and characterisation at the single bond limit

Final Report Summary - ACRITAS (Actuation and characterisation at the single bond limit)

Overview
Work performed since the beginning of the project & overview of results. ACRITAS (Actuation and Characterisation at the Single Bond Limit: www.acritas.eu) was a Marie Curie Initial Training Network which ran from Oct 1 2012 until Mar 31 2017 and whose primary focus was advanced training and research in scanning probe-based nanoscience at the single bond limit. (The Latin word for force, acritas, seemed particularly appropriate for the title of the network given that the science is driven by atomic force microscopes). The network involved eleven core partners and thirteen associate partners spanning academia, industry, professional bodies, and NGOs. See the network website, www.acritas.eu for a full list of the partners.
The scientific theme at the core of the ACRITAS training programme – measurement and manipulation at the single bond limit using scanning probe microscopes – represented an intensely exciting area of state-of-the-art scientific research. ACRITAS brought together previously distinct communities of scanning probe microscopists and theorists (in the physical and life sciences) to provide integrated training for young researchers, enabling them to develop the next generation of scanning probe methods in nanoscience (both within academia and in industry).

Project Objectives
The primary research objectives of the ACRITAS network were as follows:

■ Development of automated approaches to engineering the atomistic structure of scanning probes;
■ Identification of strategies for the atom-by-atom construction of 3D structures;
■ Developing atom tracking for ultrahigh resolution spectromicroscopy applications;
■ Development of the next generation of molecular switches;
■ To what extent can the electrostatic forces of ionic substrates be exploited to control molecular self-assembly?
■ Can we elucidate the structure and dynamics of amyloid fibril materials at the single molecule level?
■ How does the charge state of a single molecule affect its mechanical properties?
■ Mapping the properties of membrane properties and fluid-membrane interfaces with (sub)molecular resolution;
■ Can we mechanically actuate a single ion channel using an AFM tip?
■ How are the mechanical and optical properties of single polymers correlated?
■ What are the electrical and mechanical characteristics of single atom-scale defects?
■ To what extent can the “hard,dry” and “soft, wet” approaches to nanotech inform each others’ development?

In addition to these research objectives, the network focussed on providing a broad range of transferable skills training across both academic and non- academic career pathways. Furthermore, significant effort was invested in publicising key research results beyond the academic community via a variety of social media channels. The following sub-section provides a description of key research highlights stemming from ACRITAS.

The ACRITAS network has, to date, produced 25 high quality scientific papers in a range of journals. This work has spanned ultrahigh vacuum single atom/molecule manipulation, the analysis of folding of membrane proteins and the dynamics of biomolecular interactions in general, the atomistic engineering and analysis of scanning probe tips, molecular self-assembly on a variety of substrates, the automation of single atom manipulation, and a variety of ultrahigh spatial resolution measurements of single molecules and their associated force-fields and potential energy surfaces when interacting with a scanning probe.

The key training deliverables of the network have been achieved: 14 PhD students have been trained in state-of-the-art scanning probe microscopy, where a key focus of the network has been to ensure that these early career researchers graduate with an understanding of not only the power but the pitfalls of the scanning probe technique in terms of imaging and measurement artefacts. Five research highlights demonstrating key aspects of the science carried out in the ACRITAS network are included below (ACRITAS fellow’s name in italics in each case).

1. Probe-based measurement of lateral single-electron transfer between individual molecules
W. Steurer*, _S. Fatayer_ *, L. Gross, and G. Meyer. [Partner #10: IBM Zurich. *Equal contributions.]
Nature Communications 6 8353 (2015). A scanning probe was used to control and detect the charge state of individual molecules.

2. YidC assists the stepwise and stochastic folding of membrane proteins
_T. Serdiuk_, D. Balasubramaniam, J. Sugihara, SA Mari,HR Kaback, and DJ Müller. [Partner #7. ETH Zurich.]
Nature Chemical Biology, 12, 911 (2016). Single-molecule force spectroscopy elucidated the folding trajectory of a protein.

3. The electric field of CO tips and its relevance for atomic force microscopy.
_Michael Ellner_, Niko Pavlicek, Pablo Pou, Bruno Schuler, Nikolaj Moll, Gerhard Meyer, Leo Gross, and Rubén Pérez
[Partners #9 and #10 – IBM and UAM]
Nano Letters 16, 1974 (2016). A detailed analysis of ultrahigh resolution force microscope tips reveals the key role of electrostatic dipoles.

4. Increasing the Templating Effect on a Bulk Insulator Surface
_C. Paris_, A. Floris, S. Aeschlimann, M. Kittelmann, F. Kling, F. Bechstein, A. Kühnle, L. Kantorovich [Partners #2 and #5 – KCL and U. Mainz]
J. Phys. Chem. C 120, 17546 (2016). This work provides key level insights into the different bonding motifs underpinning self-assembly of molecules on insulators.

5. Automated extraction of single H atoms with STM: Tip state dependency
_M. Møller_, SP Jarvis, L Guérinet, P Sharp, R Woolley, P Rahe, and P Moriarty

[Partner 1 – Nottingham. Note, however, that there was also extensive transfer of knowledge from an associated partner, Zyvex].
Nanotechnology 28 075302 (2017). Demonstration of automated atomic manipulation and analysis of key role of tip state.