Funded Projects 2021

A tunable light source and plasmonics for selective, on-chip lysing of bio-organisms


Copyright: Dr. Irene Fernandez-Cuesta

Dr. Irene Fernandez-Cuesta (UHH)

Project partners: Sergio Diez-Cornell (DESY), Simon Joose (UKE)

The analysis of DNA at the single molecule level is crucial for many different fields in biology and medicine. It can serve to study the heterogeneity in a given population of microorganisms, to look for mutations in viruses, or to analyse tumor cells. But most of the methods available now-a-days are based on the simultaneous average of the signal from several molecules, so the information from the individual organisms is lost. In our group, we have developed a technique to analyse single molecules of DNA and obtain their genomic structural information in real time. To push the methodology even further, we need to extract the DNA from the micro-organisms or cells directly on-chip. This would avoid pipetting, molecular damage (especially critical for long, Megabasepair molecules) and loss of material. Furthermore, it would allow us to select the cell or organism that we want to investigate. Plasmonic structures can be used to create hot spots and lyse and/or analyse different bio-entities.
For this, in this project, we propose to use a versatile, high power white laser source, combined with plasmonics, to selectively lyse viruses, bacteria and cells on-chip. With this, it could be possible to select the entity, lyse it, and guide the genomic material for analysis in the same fluidic device.

Cryogenic pressure sensor for gas cooling of test masses for future gravitational wave detectors


Copyright: Dr. Christoph Reinhardt

Dr. Christoph Reinhardt (DESY)

Project Partners: Prof. Dr. Robert Blick (UHH), Dr. Axel Lindner (DESY), Hossein Masalehdan (UHH), Prof. Dr. Roman Schnabel (UHH), Dr. Udai Raj Singh (DESY)

Future gravitational-wave (GW) observatories will rely on cryogenically cooled test mass mirrors (TMMs) to achieve their ambitious target sensitivities. In the case of the European Einstein Telescope (ET), crystalline silicon mirrors will be operated at a temperature of 18 K. In a recently published preprint, we report on the theoretical finding that stabilizing TMMs at this temperature can be efficiently realized with helium gas cooling. For optimal gas cooling, all helium atoms impinging on a surface need to thermalize with this surface. This corresponds to an “energy accommodation coefficient” of unity. The actual value is lower and depends on material and temperature. As this has neither been measured nor precisely predicted theoretically, a new experiment is required. Our intended measurement relies on accurately calibrating the pressure of the helium gas coolant. As there are no commercial pressure sensors available, which fulfil our requirements, we need a new sensor.
In this project, we want to implement a nanomechanical SiN membrane oscillator, which has a gas-pressure-dependent mechanical Q factor. To resolve helium pressures relevant for gas cooling of TMMs for future GW detectors, we aim to realize a SiN “trampoline” resonator with ultra-high intrinsic Q factor . In this project, as a first step, we will characterize our sensor at room temperature in an existing UHV setup at UHH and prepare the fabrication of optimized sensors in the cleanroom at CHyN (UHH).

Nanoparticle supercrystal formation studied with coherent X-ray scattering


Copyright: Dr. Florian Schulz

Dr. Florian Schulz (UHH)

Project partners: Dr. Fabian Westermeier (DESY), Dr. Felix Lehmkühler (DESY)

Like atoms and molecules which can form crystals, nanoparticles can form so-called supercrystals. Gold nanoparticle (AuNP) supercrystals exhibit fascinating interactions with light, characterized by very strong coupling. These light-matter interactions strongly depend on the geometry and the quality of the supercrystals. Having established robust protocols for the assembly of AuNP (diameters in the range 10-80 nm) into well-defined fcc supercrystals with tunable interparticle spacing, we are now interested in more complex new structures. Examples include binary supercrystals (with nanoparticles of different sizes and of the same or different materials), supercrystals from bimetallic particles and supercrystals with small molecules incorporated into the lattice. Such structures are interesting for fundamental studies of new plasmonic band structures, and in the context of plasmonic photocatalysis and surface-enhanced spectroscopies. Despite some promising preliminary results, however, the synthesis of such structures is challenging, because the role of the different parameters in the self-assembly process is not fully understood.

We have successfully used coherent small-angle X-ray scattering (SAXS) in the past to study the structure of AuNP supercrystals in detail ex situ. To improve our understanding of the self-assembly process, in situ experiments would be highly valuable. Our robust protocol is based on evaporation of an organic solvent on a liquid subphase. We therefore propose the design and construction of a sample cell, that allows to study self-assembly on a liquid subphase with coherent SAXS in situ. The design builds upon available infrastructure at the P10 Coherence Applications Beamline (DESY). The improved understanding of the self-assembly will help us to develop robust protocols for the synthesis of new supercrystal structures to further explore this exciting class of materials. Self-assembly on liquid subphases is not only used by us, but also by many other groups studying completely different materials (e.g. the self-assembly of comparably small semiconducting nanoparticles). Once the cell is set up, it will be available at P10 for users in the future, providing interesting opportunities for in situ studies with coherent SAXS.

Correlated states and interactions in MoS2 based van der Waals hetero (homo)-structures [CorMoS]


Copyright: Dr. Chithra Sharma

Dr. Chithra Sharma (UHH)

Project Partners: Dr. Arti Dangwal Pandey and Prof. Dr. Andreas Stierle (DESY), Prof. Dr. Robert H. Blick (UHH)

Two-dimensional (2D) charge systems have been a platform for intriguing physical phenomena such as Quantum Hall effect, Berisinskii-Kosterlitz-Thouless (BKT) phase transition and, also for confined electronic devices such as quantum point contact and quantum dots. The van der Waals (vdW) materials constitute a wide category of materials that can be separated to atomically thin layers, stacked in different combinations creating a plethora of engineered heterostructures with designed properties. The semiconducting vdW materials such as MoS2 have shown to develop superconducting properties when the carrier doping is increased and fascinating many-body states such as Ising superconductivity, have been observed. Recently, it was shown that the twist angle between the layers also plays a major role in engineering the interactions.
The goal of this project is to fabricate twisted bilayer MoS2 and MoS2-graphene heterostructures controlling the angle between, performing structural characterisation, studying the superconducting properties using magneto-transport together with microwave radiation and surface acoustic waves in order to further insight into correlated electron phenomena in vdW-materials.

High-repetition-rate ultraviolet beamLine for high-statistics spectroscopy at the few-femtosecond Timescale


Copyright: Dr. Vincent Wanie

Dr. Vincent Wanie (DESY)

Project partners: Prof. Dr. Francesca Calegari (DESY), Laura Silletti (DESY), Dr. Andrea Trabattoni (DESY), Prof. Dr. Markus Drescher (UHH), Dr. Marek Wieland (UHH), Dr. Christian Brahms (Heriot-Watt University, UK), Prof. Dr. John C. Travers (Heriot-Watt University, UK)

Ultraviolet (UV) radiation has a key role in a vast range of scientific areas, including light-harvesting technologies, atmospheric chemistry and biochemistry. In laboratories, the generation and utilization of few-femtosecond UV pulses, i.e., <5 fs, is extremely challenging, but promises to reproduce ultrafast molecular processes that occur in nature and to identify their underlying mechanisms. We will exploit the recent advances of ultraviolet light sources to develop a unique UV-pump UV-probe beamline for time-resolved spectroscopy through the generation of few-cycle UV pulses at a high repetition rate (200 kHz). Such a setup will be circumventing the limited temporal resolution and signal-to-noise ratio of current state-of-the-art beamlines. The experimental scheme includes the pulse compression of an ultrafast high-power Ytterbium fiber laser using the multipass cell technology, followed by the generation of ~ 3 fs UV pulses via dispersive wave emission in a gas-filled stretched hollow-core fiber.
The output of the fiber will be coupled to a high-vacuum chamber where a dispersion-free characterization of the ultrabroadband UV radiation, another important technological challenge, will be performed using an interferometric approach that was developed at the Universität Hamburg. The light source will allow UV-pump UV-probe time-resolved experiments in which the high repetition rate will be exploited for covariance spectroscopy, benefiting from high statistics. A number of applications are envisaged, notably the investigation of UV-induced dynamics in polyatomic molecules such as amino-acids and DNA bases.