Antonio Bikić does research on philosophical aspects of intelligence with a special focus on the philosophical theory of functionalism. Functionalism claims, among other things, that the substrate and composition of an object are secondary as long as the observable function has been implemented satisfactorily, e.g., in an artificial system. One relevant concept here is »emulation« (which is also important for neuromorphic hardware) as it is based on a functionalist view of a system. Antonio is currently working on two projects that examine the extent to which the theory of functionalism is suitable to provide a comprehensive conceptual foundation for one, the question of whether teleonomic (i.e., goal-directed) processes can be realized in neuromorphic hardware. So far, teleonomic processes exist exclusively in living systems. And, second, whether and with which truth theory the actions of (spike-based) machine learning algorithms can be represented
N-heterocyclic Carbenes (NHCs) have attracted increasing attention for their use in the modification of surfaces. Their strong binding to noble metals as well as their directionality presents them as a more versatile alternative to alkyl thiols. The use of NHCs can enable tailored physical properties, high functionality and stimuli-responsiveness close the surface area. With this in mind we aim to create reversible photoswitchable NHCs and apply them as surface anchors. These motifs should undergo drastic changes to their physical properties upon irradiation or the application of other stimuli.
A01 - Development of Innovative Ligands for Adaptive Nanoparticles and Surfaces| Ravoo
Florian Bosse
In project A01 “New photoswitches for integration in adaptive nanosystems” we are working on building blocks that are responsive to (visible) light. The possibility of self-assembly via interactions like the formation of host-guest-complexes makes nanoparticles interesting for the development of adaptive materials. Therefore, we will employ our developed photoswitches in the stabilization of responsive nanoparticles.
A03 - Supramolecular Co-polymers Based on Π-Π and Metal-Metal Interactions | Fernandez
Torsten Dünnebacke
In recent studies, we have investigated the influence of certain external stimuli (pH-change, light irradiation) on the self-assembly of different OPE-based bolaamphiphiles containing a central stimuli- responsive moiety (Fig. 1 and 2).
Interestingly, we found that even with a comparable structural design of the investigated system, the type of stimulus has a great impact on the resulting supramolecular response. For example, protonation leads to significant changes in the molecular geometry, which, upon self-assembly induces the formation of distinct aggregates with different materials properties (Fig. 1). On the other hand, light-irradiation in the aggregated state leads to a completely new reaction pathway ([2+2]-cycloaddition) that is not present in the molecularly dissolved state (E-/Z-isomerization) (Fig. 2).
For the CRC 1459 Intelligent matter, I aim at synthesizing and investigating OPE-based systems containing several stimuli-responsive moieties, which can adapt to environmental changes (e.g. pH-value, light irradiation). As a consequence, the systems respond by readjusting its electronical or structural properties, therefore giving rise to new aggregation-energy landscapes forming nanomaterials with clearly distinguishable characteristics (Fig. 3). Within this project, understanding and controlling the pathways of the resulting supramolecular polymers will be the main task of my work towards the creation of new multi-stimuli responsive and adaptive nanomaterials.
My research topic is focused on the design, synthesis and characterization of tetradentate luminophoric ligands and the transition metal complexes derived from them. The emphasis is on the development of innovative coordination-chemical concepts towards multifunctional materials able to respond to the variation of externally applied potentials, gradients and fields. Hence, the influence on their photophysical properties enable multiple orthogonal readouts with spatial, temporal and spectral resolution. The interplay between ligands and metal ions (especially those with a d8 configuration, such as Pt2+ or Pd2+) facilitate exciting technological applications, including optoelectronics and biomedicine. The performance of these organometallic species is iteratively optimized by intelligent ligand design with theoretical support, which are central aspects of the research efforts in our lab.
A06 - Enzymatic Cascade Reactions for the Regulation of Biological Functions | Rentmeister
Aileen Peters
In the project A06, we are trying to engineer a biological system that responds to non-natural fuel (e.g. substrates) and changes of the environment (e.g. light). Integration of feedback loops should help to realize adaptive behavior and self-regulation. Specifically, this means that we aim to change gene expression at the level of transcription or translation in response to AdoMet analogs or their metabolic precursors (i.e. methionine analogs). To achieve this, we synthesize methionine analogs, which can be converted by engineered methionine adenosyltransferases (MATs) to the corresponding AdoMet analogs.1 MATs are self-regulated by product inhibition through AdoMet (analogs). This can be circumvented when directly coupling methyltransferases (MTases) to the MAT reaction.2 MTases use AdoMet as cofactor to methylate biomolecules. Usage of promiscuous MTases allows transferring functional groups like photocaging (PC) groups.3 If PC groups are installed e.g. in promoter regions of reporter genes, this would downregulate protein production, decreasing the fluorescence output signal. Removal of the PC-groups with light as an orthogonal trigger would restore the biological functions, resulting in again increased fluorescent output.4 In addition to MAT/MTase cascade reactions, riboswitches can influence gene expression as they actuate protein production when sensing AdoMet,5 creating another important output signal depending on the AdoMet level. My PhD project will be focused on the MAT and MTase part of the project.
References 1.Michailidou, F.; Klöcker, N.; Cornelissen, N. V.; Singh, R. K.; Peters, A.; Ovcharenko, A.; Kümmel, D.; Rentmeister, A., Engineered SAM Synthetases for Enzymatic Generation of AdoMet Analogs with Photocaging Groups and Reversible DNA Modification in Cascade Reactions. Angew. Chem. Int. Ed. 2021, 60 (1), 480–485.
2. Muttach, F.; Rentmeister, A., A Biocatalytic Cascade for Versatile One-Pot Modification of mRNA Starting from Methionine Analogues. Angew. Chem. Int. Ed. 2016, 55 (5), 1917–20.
3. Anhauser, L.; Muttach, F.; Rentmeister, A., Reversible modification of DNA by methyltransferase-catalyzed transfer and light-triggered removal of photo-caging groups. Chem. Commun. 2018, 54 (5), 449–451. 4. Heimes, M.; Kolmar, L.; Brieke, C., Efficient cosubstrate enzyme pairs for sequence-specific methyltransferase-directed photolabile caging of DNA. Chem. Commun. 2018, 54 (90), 12718–12721. 5. Batey, R. T., Recognition of S‐adenosylmethionine by riboswitches. Wiley Interdiscip. Rev.: RNA 2011, 2 (2), 299–311.
In this project we work on developing theoretical models for suspensions of refractive light-driven particles with a symmetry breaking in shape and/or refractive index profile. While models such as Active Brownian Particles (ABP) only consider the close-range repulsive interaction between particles, refractive particles can also be subject to long-range interactions mediated by the light field as well as feedback effects created by external control of the light field via optical means. This makes them a viable building block for adaptive matter.
When it comes to theoretical descriptions of classical particle systems, there are two general approaches:
Microscopic models, that describe the dynamics of each individual particle. Examples of this are Langevin dynamics1, Brownian dynamics1 or Ornstein-Uhlenbeck particles2
Field theories, that describe the dynamics of order parameter fields like density and polarization. Example of this are (Active) Phase Field Crystal (PFC) models3, Dynamical Density Functional Theory (DDFT) models4, (Active) Model B5 or (Active) Model H6
While microscopic models are typically easier for formulate based on experimental observations of individual particles, they give less insight into collective phenomena like phase transitions emerging in many-particle systems. Field theories on the other hand are harder to formulate, but give a much better theoretical grip on collective effects.
Besides the analytical methods connected to the models mentioned above we also make heavy use of numerical methods. At the level of particle dynamics this includes molecular dynamics simulations of many-particle systems as well as ray optic simulations to determine the interaction between refractive particles and a light field. At the level of field theories this mainly includes solving of partial differential equations by various means such as finite-difference or finite-element methods.
The numerical methods described above can require very large amounts of computational resources. To increase efficiency and make simulations of larger systems computationally feasible we are also invested in modern approaches to high-performance computing like offloading computations to GPUs, novel approaches to safe parallelism (Rust) or JIT-compilation via domain specific languages.
1. T. Schlick, Molecular Modeling and Simulation (Springer New York, 2002)
2. L. L. Bonilla, Physical Review E 100 (2019)
3. M. te Vrugt, J. Jeggle, R. Wittkowski, New Journal of Physics 23, 063023 (2021)
4. M. te Vrugt, H. Löwen, R. Wittkowski, Advances in Physics 69, 121–247 (2020)
5. R. Wittkowski et al., Nature Communications 5 (2014)
6. A. Tiribocchi, R. Wittkowski, D. Marenduzzo, M. E. Cates, Physical Review Letters 115 (2015)
B01 - Propulsion of Light-Responsive Nano- and Microsystems | Denz
Matthias Rüschenbaum
In our project, we design and investigate artificial light-propelled micro-swimmers. The propulsion of these particles is based on refraction of light with a net force resulting from asymmetric particle shapes and symmetry-broken refractive index profiles. Our task is the experimental realization of these particles and their subsequent light-controlled propulsion. For fabrication, two-photon polymerization (TPP) in a direct laser writing (DLW) setup is employed. Together with numerical simulations of our B01 team partners, the geometries, refractive index profiles as well as the complexly structured light used are optimized for e.g. highest velocities, followed by investigations of a high number of these particles, thereby creating artificial colloidal swarming structures. We also envisage mixtures of particles with different features including light-activated shape-changes. The ultimate goal of this project is the realization of memory effects and intelligent behavior in dense solutions of light-propelled micro-swimmers through structured illumination-based delay and added feedback
B02 - Adaptive Polymer Morphologies Through Reversible Block Fragmentation | Gröschel
Yorick Post
In our contribution to CRC 1459, we will develop dissipative block copolymer nanostructures and explore their application as sensors, actuators, and memory in synthetic adaptive and intelligent systems. Block copolymers consist of two or more covalently linked incompatible segments capable of self-assembling into complex nanostructures, such as micelles, vesicles & cubosomes. Driven by differences in chemical affinity, like solubility, the resulting nanostructure is primarily defined by the lengths of the various blocks. We are designing block copolymers that can actively alter their composition through energy-driven block fragmentation. By incorporating and tuning orthogonal and multivalent fragmentation mechanisms the stability, lifetime and self-assembly behavior of the block copolymer aqueous solution can be adjusted. The resulting out-of-equilibrium nanostructures can only exist under a sufficient energy supply. These nanostructures will be stabilized into dynamic steady states by regulating the energy supply through the implementation of intrinsic feedback mechanisms.
In project B2 we are working on block copolymer nanostructures. Using photoswitches like arylazopyrazole (AAP) in these polymers can lead to new responsive, adaptive or intelligent structures. Part of our project is implementing AAPs in a hydrophobic block of an amphiphilic block copolymer. Through the switching behavior the hydrophobicity and the conformation of the AAP can be changed and the self-assembly behavior of the polymers can be influenced. Another part is using the host-guest abilities of AAPs with Cyclodextrins to make adaptive polymer morphologies through reversible block fragmentation.
B03 - Molecular Control of Adaptive Interfaces with Photo- switchable Surfactants and Polymers | Braunschweig
Michael Hardt
Soft matter interfaces such as the air-water interfaces in aqueous foam can be used to remotely control macroscopic materials on a molecular level. Through structure-property relations the chemistry of fluid interfaces such as their molecular structure, surface charging, and surface tension and their changes to external stimuli can be transported even to larger length scales e.g. in aqueous foam.
Therefore, we use air-water interfaces as a unique platform to achieve responsive and adaptive behaviour at a molecular level that has direct consequences on material properties. For that, we are developing two subsystems A and B that respond to stimuli such as light or temperature and which can be addressed separately. Examples for subsystems developed in this project are for instance photo-switchable arylazopyrazole surfactants, spiropyrane amphiphiles as well as thermo-responsive polymers. Once the systems A and B are understood in detail and optimized with regard to their responsive behaviour, we will further focus on mixtures where the distribution of the subsystems in the bulk and at interfaces is dependent on the sequence of external triggers. The different stimuli can cause actuation that drives diffusion and subsequent adsorption to an interface. This results in a redistribution of A and B moieties from the different subsystems, where the new distribution at the interface and in the bulk provides direct feedback to a new stimulus. As a consequence, the system memorizes the nature and the sequence of the previously applied stimuli, while adaptive properties are gained by conditioned responses and training of the system.
B04 - Multistimuli sensing with memory and feedback function using photoswitchable proteins and coordination chemistry | Wegner
Alice Casadidio
We aim to create responsive matrixes such as hydrogels, which are sensitive to various inputs (from different colors of visible light to redox and pH). By combining photoswitchable proteins and coordination chemistry, we aim to achieve the formation of such materials, pursuing the development of memory due to multiple stimulation. Furthermore, we aim to investigate whether is possible to integrate signals in order to generate feedback. Together, these building blocks will give us access to processing molecular information through hydrogels.
B04 - Multistimuli sensing with memory and feedback function using photoswitchable proteins and coordination chemistry | Wegner
Saskia Frank
We will develop a hydrogel with multistimuli responsive crosslinks that can sense diverse input signals, process them following a chemically defined logic and respond with an output signal. Crosslinks will be mediated by photoswitchable proteins that convey responsiveness towards light of different wavelengths and metal coordination complexes which are sensitive towards changes in pH, redox potential and the presence of small soluble molecules. Some signals can also be integrated into the hydrogel matrix, thus creating a memory, in which I am particularly interested in my project.
B04 - Multistimuli sensing with memory and feedback function using photoswitchable proteins and coordination chemistry | Wegner
Yanjun Zheng
We aim to create new photoswitchable proteins to realize non-invasive spatiotemporal control of cell-material interactions. These proteins can be used in a wide variety of applications in the field of biomaterials, biosensing, and fundamental cell biology studies.
B05 - Investigating Molecular Forces in Focal Adhesions, Hemidesmosomes and Adaptive Hydrogels | Grashoff
Theresa Mösser
The aim of our project is the generation of a conceptually novel, biosynthetic material in which mammalian cells are utilized as information-processing elements that sense, integrate, and feedback on mechanical stimuli. Together with the Strassert and Trappmann groups, we manufacture and characterize 3D hydrogels, in which mammalian cells bestow the hybrid material with a mechanical memory. This system is monitored by fluorescent biosensors that are purified and integrated into the cell-matrix hydrogel, so that mechanical signals can be quantified with fluorescence lifetime imaging. By gradually increasing the complexity of the hybrid material, responsive and adaptive features will be incorporated.
B05 - Role of Cellular Mechanotransduction in Cell Adhesion and Migration | Trappmann
Inka Schröter
The aim of our project is the generation of a conceptually novel, biosynthetic material in which mammalian cells are utilized as information-processing elements that sense, integrate, and feedback on mechanical stimuli. Together with the Strassert and Grasshoff groups, we manufacture and characterize 3D hydrogels, in which mammalian cells bestow the hybrid material with a mechanical memory. This system is monitored by fluorescent biosensors that are purified and integrated into the cell-matrix hydrogel, so that mechanical signals can be quantified with fluorescence lifetime imaging. By gradually increasing the complexity of the hybrid material, responsive and adaptive features will be incorporated.
My research topic is focused on the design, synthesis and characterization of tetradentate luminophoric ligands and the transition metal complexes derived from them. The emphasis is on the development of innovative coordination-chemical concepts towards multifunctional materials able to respond to the variation of externally applied potentials, gradients and fields. Hence, the influence on their photophysical properties enable multiple orthogonal readouts with spatial, temporal and spectral resolution. The interplay between ligands and metal ions (especially those with a d8 configuration, such as Pt2+ or Pd2+) facilitate exciting technological applications, including optoelectronics and biomedicine. The performance of these organometallic species is iteratively optimized by intelligent ligand design with theoretical support, which are central aspects of the research efforts in our lab.
Photonic memory and computing devices are an emerging technology to be used for machine learning and artificial intelligence applications. We use chalcogenide phase-change materials (PCM) to implement memory functionality in the integrated photonic circuits. In our research, light from a waveguide couples evanescently to a PCM patch which influences the transmission through the waveguide depending on the phase state of the PCM. By decreasing the size of the PCM volume, the switching speed can be increased while the needed switching energy can be decreased. Additionally, we use plasmonic nanoantennas to enhance the interaction between the electric field and the PCM. Therefore, we develop a method to fabricate nanometer-sized PCM cells embedded in the gap of gold dimer nanoantennas on a waveguide. These devices are promising candidates for the use in material learning, machine learning in materio, and pattern recognition applications.
C03 - Self-Assembly of Hybrid Nanostructures for Neuromorphic Electronics | van der Wiel
Marc Beuel
Previous research1 has shown that disordered networks of functionalized nanoparticles can be configured to behave like Boolean logic gates and classifiers. The functionalized nanoparticles act as single-electron transistors, i.e. strongly nonlinear periodic switches, while the organic ligands act as tunable tunnel barriers that add memory functionality to the network. The purpose of this research project is to build on these results and enhance the functionality by introducing various novel organic ligands and magnetic nanoparticles to enhance the addressability and to introduce memory to tackle new time-dependent problems and realize artificial neural networks that will pave the way for new applications of energy-efficient in-materio computing.
Reference:
1. Bose, S., Lawrence, C., Liu, Z. et al. Evolution of a designless nanoparticle network into reconfigurable Boolean logic. Nature Nanotech10, 1048–1052 (2015)
C03 - Kinetic Monte Carlo Model for Computing Functionalities in Nanoparticle Networks | Heuer
Jonas Mensing
The theoretical underpinning of the experimentally studied nanoparticle networks is investigated by developing a physical model and subsequent simulations. For this purpose, a highly optimized parallel C++ code is being developed in order to model the charge transport within the electrically tunable network stochastically, i.e. with a Kinetic Monte Carlo approach. Requirements for computing functionalities such as Boolean logic and memory functionalities based on intelligent materials are examined. Therefore, statistical and data-driven tools are being developed to investigate the effects of different materials and system sizes. A close comparison with corresponding experiments on nanoparticle networks will be performed.
C03 - Self-Assembly of Hybrid Nanostructures for Brain-Inspired Electronics | Ravoo
Lisa Schlichter
We want to achieve reconfigurable computational functionality in a designless nanoparticle network for unconventional computing using artificial evolution in nanoscale materials. Therefore, hybrid organic-inorganic nanostructures based on the assembly of nanoparticle networks connected by junctions composed of tailor-made organic ligands are constructed. Gold nanoparticles act as single electron transistors while organic ligands act as tunable tunnel barriers introducing synaptic, tunable memory.
C04 - Spin Wave Systems for Reservoir Computing | Pernice
Dmitrii Raskhodchikov
Today, scientists are actively looking for a replacement for conventional electronics. One of the promising areas is spintronics - where information is transmitted not directly by electrons, but by means of spin. This approach allows operations to be completed faster and significantly improves the energy efficiency of devices. The propagation length of spin-waves in amorphous yttrium iron garnet (YIG) is sufficient for the use of this material in electronics and it combines well with existing materials both during operation and in production. The quanta of spin-waves are magnons: the dynamic eigen-excitations of a magnetically ordered body. Analogous to electric currents, magnon-based currents can be used to carry, transport and process information. The use of magnons allows the implementation of novel wave-based computing technologies free from the drawbacks inherent to modern electronics, such as dissipation of energy due to Ohmic losses. We will realize adaptive magnonic networks in a complex system comprised of a large number of coupled spin-waveguides, which transform the input of electrical data into spatiotemporal patterns in a high-dimensional space using nonlinear interference of spin-waves.
Processing artificial neural networks requires powerful hardware. Today, they are usually calculated on conventional computers based on the von Neumann architecture. In this architecture, the processing unit is separated from the memory. Moving data from the memory to the processing unit, however, is costly in terms of time and energy. Hence, collocating processing and memory in so-called in-memory computing systems can make these calculations significantly more efficient. A novel and promising approach are systems based on integrated photonics. Here, optical signals are passed through waveguides and the weight of artificial synapses are represented by analog memory cells. I am working on mixed electro-optical memory cells based on phase-change materials. In such devices, a thin film of phase-change material is located on top of a photonic waveguide. The transmission through the waveguide can be tuned based on how much of the material is crystalline, and how much is amorphous. This can be probed with short laser pulses, taking advantage of the high data modulation rate and low latency of photonic systems. The state of the phase-change material can be changed by local heating with an electrical current. To optimize the performance of the electro-optical devices, I also study new materials with optimal properties. Utilizing both the electrical and optical domain in a single system is beneficial for learning, contributing to the development of intelligent matter.
