KorevaarLab
Research
In our research, we aim to arrive at self-organizing matter by exploiting phenomena that emerge from unique combinations of self-assembly, chemical reaction networks and physical chemistry phenomena such as surface tension phenomena. These movies (↑) feature an example of our research: We have developed self-assembling structures (“myelins”) that organize themselves into wires and networks at the millimeter length scale – in a (primitive) analogy to the growth of slime molds in nature [BOX 1].
Over the past few years, we have demonstrated – for example – how we can grow these myelin connections towards particular nodes in a network upon localized photochemical stimulation, and how we can use them to direct the motility of other droplets [BOX 2]. Furthermore, these myelins can serve as dynamic pathways that guide the growth of electrodeposited copper dendrites – providing dynamic connections amongst electrodes [BOX 3].
We are interested in developing chemistry that introduces life-like behavior in synthetic matter. Synthetic materials as we use them nowadays are typically “static” and limited to just one function. Living materials however sense what happens in their environment, and reorganize to self-optimize themselves to particular tasks. For example, slime molds grow long wires toward places where food is available, and neurons communicate through dynamic connections in our brain. Inspired by these examples, we aim to open entirely new possibilities in intelligent matter: Imagine for example self-organizing device interfaces that “determine” the path for a sample in lab-on-a-chip applications, or self-assembling filaments that in analogy to neurons establish dynamic connections in neuromorphic circuits.
BOX 1: Myelins forming dynamic networks at air/water interfaces. Our interconnected filament-droplet networks spontaneously emerge, when microliter-droplets of a C12E3 or C12E4 amphiphile are deposited at an air-water interface. The assembly of myelins starts with a lamellar phase of bilayers at the boundary of the amphiphile droplet (“source”). The spaces in between these bilayers take up more water; forcing the bilayers to buckle and form myelins that progress over the air-water interface. When a droplet of a hydrophobic liquid (“drain”) is deposited, it takes up amphiphile surfactants from the air/water interface, such that a surface tension gradient emerges: driving a Marangoni flow that draws the myelins from the source towards the drain. Complementary to Marangoni flows that repel drains from sources, myelins that tether to the drain will generate elastocapillary effects that draw the drain back: establishing interconnected droplet networks when these effects are balanced.
Our first paper where we released this system:
Nature Communications 2020, 11, 4800
More details on the mechanism, including experiments and a model to assess the Marangoni flow patterns, and studying of the elastocapillary attraction.
Langmuir 2022, 38, 10799−10809
Or check out this article by NEMO Kennislink (in Dutch).
BOX 2: Orbiting self-organization of filament-tethered surface-active droplets.
We demonstrated an out-of-equilibrium self-organization of oil-based droplets that start to orbit around a C12E3-based droplet that grows myelins. In brief, the oil-droplet functions as a drain and attracts a Marangoni flow as well as myelins from the source, which together balance the relative source-drain positioning – in analogy to the system shown in Box 1. On top of that, the drain contains pivalic anhydride, which hydrolyses slowly upon contact with water and thereby results in a “trail” of pivalic acid that is left behind the moving droplet. Pivalic acid destabilizes the myelins, such that they cannot tether to the back of the droplet anymore. As a result, myelins adhere selectively to the side and front of the drain droplet, such that the elastocapillary attraction draws the drain forward – resulting in a unique orbiting motion of the drain around the source droplet (which can be either left- or right-handed).
BOX 3: Myelins as dynamic pathways guiding the growth of electrodeposited copper dendrites.
We use our myelin assemblies as dynamic pathways to guide the growth of electrodeposited copper dendrites. To this end, we discovered a unique interaction between myelin assemblies that deliver copper(II) ions to the tips of copper dendrites, which in turn grow along the Cu2+ gradient upon electrodeposition. Cu2+ can get electrodeposited at a negative electrode, generating metallic structures (“dendrites”) which direct away from the electrode, due to electrostatic repulsion, such that they reach out to the surroundings for new copper(II) ions to be added to the growing tips. Next, Cu2+ ions can be loaded via copper(II)chloride into the myelins, providing a copper(II) supply for the dendrites, which grow along the myelins towards the copper(II)-loaded source droplet – against the outbound Marangoni flow.
If a positive electrode is positioned in the source droplet, copper dendrites can rapidly grow from multiple (-) electrodes to establish a connection. Next, we can make the connections reconfigurable by exploiting the outbound Marangoni flow to push off “old” connections from inactive electrodes, while new connections grow upstream from an active electrode that supplies the electrons for copper dendrite deposition. We envision that our approach provides novel strategies for controlled growth of solid wires along directed gradients, and ultimately opens pathways for reconfigurable connections in adaptive networks.
J. Am. Chem. Soc., 2024, 146, 28, 19205–19217
Other recent highlights of our work include:
Predator-prey behavior of droplets propelling through self-generated channels in crystalline surfactant layers. We report a unique strategy to use crystalline surfactant layers formed at air/water interfaces to sustain the propulsion of floating droplets, and at the same time shape paths for other droplets attracted by them. Decylamine forms a closed, crystalline layer that remains at the air/water interface. We show how aldehyde-based oil droplets react to the decylamine in the crystalline layer by forming an imine, causing the droplets move through the layer while leaving behind a millimeter-wide open channel (like in the “Pac-man” game). Next, our C12E3 droplets get attracted to the aldehyde droplets (which function as a drain): Causing the C12E3 droplets to chase, and ultimately catch, the aldehyde droplets along the channels they have created. Together, our results feature a predator-prey analogy, that is for the first time established at an air/water interface.
Angewandte Chemie Int. Ed. , 2025, e202502352
We show how the trajectory of the myelins can be directed towards selected photo-active droplets upon localized UV exposure. Furthermore, we establish re-configurability of the connections amongst various droplets, and we demonstrate a photo-controlled transport of fluorescent dyes by the myelins – as an example of chemical communication through the self-assembled connections.
J. Am. Chem. Soc., 2024, 146, 6006-6015
Inspired by Wolpert’s concept of positional information – pattern formation based on cells’ positions in morphogen concentration gradients – we demonstrate the self-organization of surfactant droplets floating at an aqueous solution into ‘French flag’-patterns. In short, a pH-dependent surfactant that competes with the myelin assembly leads to position-dependent myelin growth and droplet-droplet repulsion in a pH-gradient. To generate a large field of floating surfactant droplets (n = 50), we developed a robotic deposition platform together with labm8.io
We established the concept of quorum sensing – known to orchestrate collective behavior in unicellular organisms – in emulsion droplet systems. Initial repulsion between droplets upon surfactant release is counteracted when the droplets release sufficient surfactant precursor that suppresses the repulsive surface tension gradients, providing droplet clustering selectively above a critical droplet density.
Advanced Science 2024, 11, 2307919
Our perspective article on “Spatial programming of self-organizing chemical systems using sustained physicochemical gradients from reaction, diffusion and hydrodynamics”.
Phys. Chem. Chem. Phys., 2022, 24, 23980−24001