Videos
This is a 3D animation illustrating a technological process patented by the company CADENAS p.s.a. The process leads to the efficient creation of innovative structures from micro-particles, which allow for cost-effective and environmentally friendly production of electrically highly conductive micro-tracks from commonly available raw materials, including recycled ones. Such micro-tracks can find wide application in electronics, including in photovoltaics.
This work has been patented and is currently in force in several countries. EP3831171B1 link
This video shows the preparation and initialization of a particle chain experiment. Stainless steel capillary with a 1.3 mm inner diameter is filled with 250 μm stainless steel particles suspended in silicone oil (viscosity: 150 mPa·s). A voltage of 1.25 kV is applied to the capillary, while the glass substrate remains ungrounded.
This work was published in Materials & Design 255, 114160 (2025) link
Watch a chain of 200 μm solder particles form and collapse under its own weight. The chain is formed using voltage of ~0.25 kV, 1 kHz. Initially, the chain remains stable and fully suspended at the dispersion meniscus until approximately t = 70 s. As the chain reaches its critical mass (and thus its critical length), gravitational forces overcome capillary forces, causing the lower portion of the chain to progressively sag and accumulate particles on the substrate. Around t = 90 s, the conduit motion is halted; however, chain formation continues at the meniscus while the excess portion descends and accumulates on the substrate. Video speed: 5×.
This work was published in Materials & Design 255, 114160 (2025) link
This video illustrates 3D simulation results showing the stages of shape deformation of Sn63Pb37 particles under compression in two configurations: two particles in contact (left panel) and a segment of an infinitely long particle chain (right panel). Contact areas between neighboring particles are highlighted in blue.
This work was published in Soft Matter 21, 4393–4406 (2025) link
This video shows 2D simulation results illustrating the distribution of equivalent (local) stress (left) and local strain rate (right) within a symmetrical cross-section of a sphere under uniaxial compression. The simulation is based on the Johnson–Cook (J–C) model and uses an applied engineering strain rate of 0.1/sec.
This work was published in Soft Matter 21, 4393–4406 (2025) link
The results of COMSOL simulations on the compressive deformation of a particle chain are presented. The left panel displays the evolution of particle shapes and changes in their contact area (highlighted in blue). The accompanying plot illustrates quantitative changes in the contact area between two adjacent microparticles. The simulated balls in the chain initially have a diameter of 760 µm.
This work was published in This work was published in Materials & Design 253, 113985 (2025) link
A particle chain consisting of seven 300-µm Sn63Pb37 spheres, deposited on the device-under-test (DUT) carrier. The orange areas are two copper electrode pads. The film is recorded from above the compression glass slide, in the direction of compression. On the lower panel, an animation obtained from COMSOL simulations is presented.
This work was published in Materials & Design 253, 113985 (2025) link
3D visualization of our custom-built experimental set-up for measuring the resistance of a particle chain under mechanical compression. The system includes an impedance analyser (Zurich Instruments) with a test fixture, a digital microscope for top-view observation, and translational stages to move a compression slab. The particle chain, made of nearly identical microparticles, is placed between two copper pads on a specially designed PCB carrier. A thick glass slab, precisely positioned with sub-micrometre accuracy, compresses the particles during measurements.
This work was published in Materials & Design 253, 113985 (2025) link
In this video, we delve into the innovative world of particle microstructures. The focus is on the unique electronic properties of these structures, highlighting how they can serve as cost-effective and efficient conductive paths compared to traditional materials like nanoparticles or liquid metals. The video demonstrates a straightforward process of creating conductive micropaths: starting with a chain of hundreds of solder balls, each about 200 micrometers in diameter. This chain is then deposited onto a glass substrate through the coordinated movement of the substrate and a lowering electrode, to which the particle chain is attached.
The deposited particle chain can then be studied from both mechanical and electrical perspectives. We are conducting various experiments, testing different methods of chain post-processing leading to the enhancement and tuning of the electrical conductivity of the new microparticle structures.
This work was published in Materials&Design 223, 111233 (2022) link
Bringing an electrode to the surface of a liquid containing microparticles can be used to extract surprisingly long chains of these particles. Interestingly, these particles are held together by a thin liquid layer that covers them. The phenomenon visually resembles a crucial modern-day technological process, namely, Prof. Jan Czochralski's method of growing monocrystals, which involves slowly extracting a rod-mounted seed crystal from molten material. The materials fabricated using Czochralski's method are regular crystals in all three dimensions, whereas our structures are composed of microparticles arranged regularly along only one dimension. Therefore, with some leeway, our chains might be considered as one-dimensional crystals. This phenomenon, discovered by our group, shows promise for a broad variety of applications, including in electronics.
This work was published in Nat. Commun. 8, 15255 (2017) link
The 1D structures of microparticles are formed through complex electrical, gravitational, and capillary interactions. Gravity, however, acts as a limiting factor; if a chain becomes too heavy, it is severed by the force of gravity. Evidence suggests that such chains could also form in zero gravity, potentially reaching any length. The length of these particle chains varies with the number, weight, and size of the microparticles. In our experiments, we used particles with diameters ranging from about 100 nanometers to 200 micrometers. Chains formed from micron-sized particles contained up to several thousand elements and reached lengths of several centimeters. We observed viability across a wide range of particle sizes, including approximately 100 nm, 15 µm, 25 µm, 55 µm, 100 µm, and 200 µm.
This work was published in Nat. Commun. 8, 15255 (2017) link
Once formed, the 1D particle structures behave like flexible chains that can be bent into various shapes. However, their flexibility greatly depends on the type of liquid used. For instance, in certain experiments, chains were extracted from molten paraffin wax. These structures quickly solidified after extraction, becoming rigid. An intermediate option is achieved by blending substances like resin and alcohol; as the alcohol evaporates, the resin hardens, resulting in a chain that is less flexible but not entirely rigid. The chains formed through our electric method remain stable even after the external field is turned off. They are held together by sphere-sphere liquid bridges, which afford them sufficient flexibility to bend. This unique combination of properties allows for the subsequent deposition of the formed chains into targeted patterns through direct writing.
This work was published in Nat. Commun. 8, 15255 (2017) link
We've all probably seen our mothers, or grandmothers, wear necklaces made of beads strung on a thread. The chains of microparticles fabricated and studied by our team look very similar, but they are much smaller. However, what's truly fascinating is the physics behind this process. The formation of these regular structures is determined by a set of phenomena that are far from trivial, with the role of the thread that holds together the individual beads played by a liquid. Interestingly, unlike a traditional necklace where the thread passes through the beads, in our case, the liquid 'thread' actually coats the microparticles.
This work was published in Soft Matter 13, 4698–4708 (2017) link
Capillary bridges can be used for fabricating new materials and structures. We theoretically describe and experimentally validate the mechanism of formation of capillary bridges during the process of extracting a beaded chain from a liquid with a planar surface. There are two types of capillary bridges present in this system. The first is the sphere-planar liquid surface bridge, initially formed between the spherical bead exiting the liquid bath and the planar liquid surface. The second is the sphere-sphere capillary bridge, formed between adjacent beads in the part of the chain above the liquid surface. As the chain is pulled out of the liquid, the sphere-planar liquid surface bridge transforms into the sphere-sphere bridge. We show that this bridge transition can be either continuous or discontinuous, depending on the size of the beads. Specifically, the transition is continuous when the diameter of the spherical beads is larger than the capillary length.
This work was published in Soft Matter 13, 4698–4708 (2017) link
Electrically insulating objects immersed in a weakly conducting liquid may electrorotate when subjected to an electric field. In this video, four polystyrene particle‐covered droplets (diameter 0.22–1.02 mm) exhibit varying rotation rates when subjected to different electric field strengths (125–835 V/mm). Compared to pure droplets, we found that adding particles to the droplet interface significantly alters the electrorotation parameters. In our research, we detailed the deformation magnitude, orientation, and rotation rate of a droplet subjected to a DC E-field.
This work was published in Soft Matter 17, 5006–5017 (2021) link
Electrorotation can be used to mix particles and to study the solid-to-liquid transition of the particle layer. This video features a droplet, approximately 2 mm in diameter, covered with 50-μm polyethylene particles (red and cyan) forming a Janus shell, subjected to an electric field of 700 V/mm. Initially, before the electric field was applied, the particles in the shell were jammed, preventing mixing. Once the electric field was activated, the particles began to mix, causing the border between the differently colored particle shells to break up. Eventually, after several minutes of electrorotation, the particles were almost completely mixed. The video was accelerated, first to 4 times and then to 10 times the normal speed.
This work was published in Soft Matter 17, 5006–5017 (2021) link
Our experimental results reveal that both the critical electric field (for electrorotation) and the rotational rate depend on droplet size, particle shell morphology (smooth vs. brush-like), and composition (loose vs. locked particles). In this video, we present the electrorotation of droplets (with a diameter of around 1.39 mm) featuring rigid and deformable shells made of polyethylene (PE) particles. The rigid shell was created by fusing particles together with microwave heating. When heating a PE particle-covered droplet, hairy polymeric structures formed, protruding from the shell. The droplet with a hairy shell rotated significantly slower than its smooth-shelled counterpart, due to an increased drag coefficient.
This work was published in Soft Matter 17, 5006–5017 (2021) link
A variety of approaches have been developed to release contents from capsules, utilizing techniques such as electric or magnetic fields, light, or ultrasound as stimuli. However, in the majority of these approaches, capsules are disintegrated in a violent way, and the release of the encapsulated material often occurs in random directions. Thus, achieving controllable and direction-specific release from microcapsules in a simple and effective manner remains a significant challenge. This limitation hinders the use of microcapsules in applications requiring targeted and directional release. Here, we present a convenient ultrasonic method for controllable and unidirectional release of an encapsulated substance. The release is achieved by using ultrasound at MHz frequencies, which facilitates the stretching of the inner liquid, imposing mechanical stress on the capsule’s shell. This leads to the puncturing of the shell and allows for the controlled, unidirectional release of the liquid payload.
Published in ACS Appl. Mater. Interfaces, 12, 15810–15822 (2020) link
Droplets, much smaller than the ultrasound wavelength and located in the periodic ultrasound field, are acoustophoretically driven toward the nodal positions of the standing wave. However, a droplet whose size is comparable to or larger than half the ultrasound wavelength stretches along the direction of wave propagation and can span several wavelengths. This mechanism of stretching, originating from the acoustic radiation stress acting on a droplet’s surface, is used for rupturing shells and liberating the inner liquid from capsules.
Published in ACS Appl. Mater. Interfaces, 12, 15810–15822 (2020) link
This study examines the crumpling of deformed particle shells formed on the surface of droplets. Wrinkling in a particle shell occurs in areas where compressive stress exceeds the shell's elastic tension and the droplet interface's surface tension. We demonstrated that applying an electric field can effectively probe the thickness and bending stiffness of particle shells on emulsion droplets by inducing shell wrinkling. Our experiments revealed that on curved interfaces, multiple wrinkles with characteristic wavelengths are formed; these wavelengths increase with larger particles and on larger droplets.
Published in ACS Appl. Mater. Interfaces, 11, 29396–29407 (2019) link
We developed a method for controlling the packing of particles within a monolayer shell formed on a droplet. A particle-covered droplet is subjected to an AC electric field that changes periodically, with a period slightly shorter than the time needed for electrical charges to build up on the droplet's interface. The particle shell underwent deformation cycles where it was compressed and stretched. After 50 deformation cycles, the particle packing density increased from 0.73 to 0.78, and most of the horizontal wrinkles observed at the beginning of the experiment were smoothed out. The applied electric field was oriented horizontally.
Published in ACS Appl. Mater. Interfaces, 11, 29396–29407 (2019) link
Electric field-induced crumpling of the particle shell on a droplet. A particle shell, composed of polyethylene particles (approximately 3 µm), formed on a 2-mm silicone oil droplet. Initially, without an electric field, the shell maintained a spherical shape. The shell was then exposed to an electric pulse (lasting 1 second), resulting in deformation. Once the electric field was deactivated, the shell relaxed back towards a spherical shape, causing the particle film to crumple. As the particle shell relaxed and re-covered the droplet, the wrinkles vanished.
Published in ACS Appl. Mater. Interfaces, 11, 32, 29396–29407 (2019) link
The process of the particle shell opening and closing visually resembles the dilation and constriction of a human eye's pupil, or the operation of an optical diaphragm. This inspired our demonstration of using particle-covered droplets as millimeter-sized diaphragms with adjustable apertures to control light passage. When the droplet was subjected to a DC electric field, an opening formed in the particle film at the droplet's electric pole, allowing laser light to pass through. Once the electric field was turned off, the particles re-covered the entire droplet, consequently blocking the laser light again.
Published in ACS Appl. Mater. Interfaces 11, 25, 22840–22850 (2019) link
A silicone oil droplet (approximately 3 mm in diameter) covered with polyethylene particles (around 20 µm) was viewed perpendicular to the electric field direction. The droplet was surrounded with castor oil, and docked in an O-ring that was fastened to one of the electrodes. In the presence of a DC electric field, electric stress caused deformation of the droplet, which allowed the particles to unjam and electrohydrodynamic (EHD) flows to emerge. These EHD flows transported particles away from the droplet's electric pole, creating a particle-free area. This active, tunable, and reversible opening and closing of particle shells on droplets could facilitate chemical reactions within droplets and enable various small-scale laboratory operations, including online detection, measurement, and adjustment of the droplet's liquid.
Published in ACS Appl. Mater. Interfaces 11, 25, 22840–22850 (2019) link
This video demonstrates the formation of a droplet covered with densely packed particles. Convective electrohydrodynamic (EHD) liquid flows facilitate the creation of a monolayer film, with densely packed particles arranged in an almost hexagonal pattern. Silicone oil droplets covered with red polyethylene particles (average size approximately 50 µm) were formed in castor oil using a micropipette. The particles were transported to the interface of the silicone oil droplet by applying a DC electric field.
Published in ACS Appl. Mater. Interfaces 11, 25, 22840–22850 (2019) link
We proposed a novel bulk method for fabricating Pickering emulsions using electric fields. We prepared oil-in-oil emulsions stabilized by microparticles and controlled the mean size of the Pickering droplets. Our approach leverages the reduction of total surface area in emulsion droplets through electrocoalescence. This process resulted in increased particle coverage, eventually leading to the formation of densely packed particle shells on Pickering droplets. First, we prepared an unstable pre-emulsion, characterized by droplets with small sizes and low particle coverages. From this, the final Pickering emulsion was formed through consecutive coalescence events, accelerated by the application of an electric field.
This work was published in Soft Matter 14, 5140–5149 (2018) link
Actively arranging surface-adsorbed conductive particles by switching the electric field frequency from 0 Hz (EHD flow regime) to 200 Hz (particle dipolar interaction regime). A silicone oil droplet with a diameter of approximately 3 mm is viewed from two perspectives: along (left) and perpendicular (right) to the electric field direction. Ag-coated glass microspheres, with an average diameter of approximately 20 µm, were used in this experiment. The structuring process is reversible, with the switch between the two particle conformations occurring within seconds. We also observed that particles on the droplet's surface exposed to a constant DC electric field exhibit different structuring depending on their electrical properties and coverage.
This work was published in Soft Matter 14, 5442–5451 (2018) link
A designed assembly of particles at liquid interfaces offers numerous advantages in material development and can be achieved through various methods. Electric fields serve as a flexible approach for arranging particles on droplets, utilizing electrohydrodynamic circulation flows, as well as dielectrophoretic and electrophoretic interactions. The manipulation of particles is influenced not only by the characteristics of the applied electric field but also by the inherent properties of the particles themselves. For instance, slightly more electrically conductive polystyrene particles tend to form chains, while pristine polystyrene particles are typically drawn towards the electric poles of a droplet.
This work was published in Materials 10(4), 329 (2017) link
Two silicone oil droplets, each covered with microparticles, are formed in castor oil. An external DC electric field is applied horizontally, driving the droplets toward each other through attractive EHD and electrostatic forces, facilitating their coalescence. Upon coalescing, a Janus shell rapidly forms within a few seconds. The merged droplet is then completely enveloped by particles. During coalescence, the particles are able to move and reorganize, but only within the droplet surfaces, due to strong desorption energies. These particles are closely packed on the droplet's surface, arranging themselves in slightly disordered hexagonal patterns. Deactivating the electric field does not cause any noticeable movement of the particles within the shell, indicating the shell's stability.
This work was published in Nat. Commun. 5, 3945 (2014) link
Janus, the ancient Roman god known for his two faces looking in opposite directions, has long captured the fascination of believers. Similarly, Janus capsules, consisting of two shells adhered to each other and each made from micro- or nanoparticles with distinct properties, have been attracting considerable interest in the research community. These capsules are viewed as promising tools for drug delivery and as vehicles for the creation of innovative materials. However, to make Janus capsules widely accessible, efficient mass production methods need to be developed. In our work, we introduce a method for fabricating patchy shells on droplets, potentially paving the way for scalable production of Janus capsules.
This work was published in Nat. Commun. 5, 3945 (2014) link
At low particle coverage on a droplet's surface, intensifying the electric field strength triggers instability in the particle ribbon, causing it to fragment into several counter-rotating colloidal assemblies. The number of these domains is influenced by the strength of the electrohydrodynamic flows of the liquids, and the frequency of domain rotation is directly proportional to the electric field strength. In our subsequent research, we highlight the significance of the electrical properties of particles in their assembly on the droplet's surface, as well as the diminution of convective liquid flows induced by the electric field.
This work was published in Nat. Commun. 4, 2066 (2013) link
Colloidal particles are transported by electrohydrodynamic (EHD) convective flow, resulting in their concentration into a densely packed colloidal ribbon on the droplet's surface. This phenomenon is similar to the 'coffee-ring' effect, where colloidal particles are carried by capillary convective flow in an evaporating droplet. The ribbon's formation encompasses two primary processes: the transport of particles from the bulk of the droplet to its surface, and the subsequent assembly of the ribbon film on this surface. The last two videos in the series showcase the assembly of particles that are already present on the surface of a droplet, observed both along and perpendicular to the electric field direction.
This work was published in Nat. Commun. 4, 2066 (2013) link
The inception of our laboratory and the soft matter group dates back to 2013. The HOMING grant from the Foundation for Polish Science (FNP) was instrumental in this journey, providing the necessary funds for procuring tools and materials to establish a cost-effective experimental setup and offer stipends to MSc students. Our initial experimental setup was established at the Institute of Physical Chemistry of the Polish Academy of Science, where I had the opportunity to work for two years. My growth as a scientist was significantly influenced by Prof. Piotr Garstecki and his team. My fully independent scientific journey began in 2015 when I was offered both a laboratory and office space at the Faculty of Physics, Adam Mickiewicz University, Poznań, Poland. This opportunity allowed me to expand my research group and accelerate our scientific endeavors. I am deeply grateful to my Ph.D. supervisor, Prof. Jon Otto Fossum, for his guidance and for introducing me to the realm of fundamental science. In this video, I discuss the process of fabricating particle shells on droplets and my experiences with the scholarship received from the FNP.