Periodic Reporting for period 4 - PrintPack (Arranging the Particles: Step Changing Chemical Measurement Technology)
Okres sprawozdawczy: 2021-04-01 do 2022-09-30
The PRINTPACK project aims at developing a fabrication method to produce perfectly ordered 3D-materials composed of 3D-networks of spherical (functionalized) microparticles. One key application for this novel type of meta-materials is liquid chromatography (LC). LC is the current state-of-the-art chemical separation method to measure the composition of complex mixtures. Driven by the ever-growing complexity of the samples in e.g. environmental and biomedical research, LC is constantly pushed to higher efficiencies. Using highly optimized and monodisperse spherical particles, randomly packed in high pressure columns, the progress in LC has up till now been realized by reducing the particle size and concomitantly increasing the pressure. With pressures already up at 1500 bar, this approach has now reached its limit while groundbreaking progress is still badly needed, e.g. to fully unravel the complex reaction networks in human cells.
For this purpose, it is proposed to leave the randomly packed bed paradigm and move to structures wherein the 1 to 5 micrometer particles currently used in LC are arranged in perfectly ordered and open-structured geometries. This has been pursued using the latest advances in nano-manufacturing and positioning and developing an inventive high-throughput particle assembly and deposition strategy.
The project led to the development of a new method for the production of ordered micro-particle layers with freely selectable pattern using a combination of electrostatic levitation and vacuum aspiration. The produced layers can subsequently be deposited to a stack of previously deposited layers. Next to the ability to produce perfectly ordered LC columns, this opens the road to a new type of particle printing with applications to all fields requiring ordered 3D structures, such as e.g. photonic crystals.
For this purpose, it is proposed to leave the randomly packed bed paradigm and move to structures wherein the 1 to 5 micrometer particles currently used in LC are arranged in perfectly ordered and open-structured geometries. This has been pursued using the latest advances in nano-manufacturing and positioning and developing an inventive high-throughput particle assembly and deposition strategy.
The project led to the development of a new method for the production of ordered micro-particle layers with freely selectable pattern using a combination of electrostatic levitation and vacuum aspiration. The produced layers can subsequently be deposited to a stack of previously deposited layers. Next to the ability to produce perfectly ordered LC columns, this opens the road to a new type of particle printing with applications to all fields requiring ordered 3D structures, such as e.g. photonic crystals.
On the theoretical side, correlations for the dependency of the dispersion coefficient and the local Sherwood number as a function of the Peclet number have been established. These calculations define a new yardstick for the chromatographic performance of perfectly ordered structures. This work has been published in the Journal of Chromatography (Matheuse et al., 2020). Two more papers in the Journal of Chromatography (Desmet et al., 2020a-b) were devoted to the discovery of a new mode hydrodynamic dispersion regime in ordered flow-through media. The unique feature of this regime is that it represents a local decrease of the dispersion, whereas in all other regimes the dispersion increases monotonically with the velocity.
Next, a radically new computational approach allowing to study dispersion problems using steady-state computations instead of the conventional time-dependent simulations has been developed. This work, based on the age field theory, has already led to two fundamentally new insights (logarithmic dependence on the velocity as a characteristic trait of randomly fluctuating velocity fields; logarithmic growth of plate heights with length and width in systems with radial velocity bias) which are in the course of being submitted to the Journal of Fluid Mechanics and Analytical Chemistry.
Concerning the core goal of the project, i.e. developing a rapid large-scale method to produce ordered 2D sphere arrays, an important breakthrough was realized by generating stable particles clouds using an electrostatic cell as a means to present the particles to the vacuum-driven assembly membranes. This work has been published as a cover article in Materials & Design (Van Geite et al., 2022) and in Powder Technology (Jimidar et al., 2021) and offers a new method to produce for the rapid (<1s) assembly of high quality monolayers (errors <0.1% measured over large repeat series). We also demonstrated these can subsequently be deposited onto a second surface. Unfortunately, this surface is currently limited to soft surfaces and not to the rigid surface that are needed to 3D print particle assemblies. The electrostatic particle cloud generation method produced more repeatable and flawless layers than those obtained with the wet assembly processes and the pressure-shock method (both published in Powder Technology: Berneman et al., 2020 and Van Geite et al., 2022) we initially mainly focused on.
Another major finding in the project has been the development of a method to uniformly fill an array of circular pockets with single particles. This technique has subsequently been applied to fill networks of interconnected pockets (so-called structured micro-grooves) to produce perfectly ordered particle beds for miniature-scale chromatography. This work has been reported as a cover story in Langmuir (Verloy et al., 2022) and protected by means of a European patent application.
As an unexpected result, we discovered a new method for the directed particle segregation & self-assembly of silica particles by rubbing-induced tribo-electrification on patterned surfaces (pattern of fluorocarbon coated patches). Our key finding is the fact that silica particles are tribo-charged due to the rubbing process and therefore stick on the fluorocarbon coating, while they are repelled from the silicon regions in between the fluorocarbon patches because of the opposite charge. During the rubbing, a monolayer of particles is on the fluorocarbon surfaces, thus creating an ordered array of self-assembled particle collections. Using Kelvin Probe Force Microscopy (KPFM), we could show that the rubbing process induces electric charge on the FC coated surface and particles. This work was published in Langmuir (Jimidar et al., 2020) and in Soft Matter (Jimidar et al., 2020).
Next, a radically new computational approach allowing to study dispersion problems using steady-state computations instead of the conventional time-dependent simulations has been developed. This work, based on the age field theory, has already led to two fundamentally new insights (logarithmic dependence on the velocity as a characteristic trait of randomly fluctuating velocity fields; logarithmic growth of plate heights with length and width in systems with radial velocity bias) which are in the course of being submitted to the Journal of Fluid Mechanics and Analytical Chemistry.
Concerning the core goal of the project, i.e. developing a rapid large-scale method to produce ordered 2D sphere arrays, an important breakthrough was realized by generating stable particles clouds using an electrostatic cell as a means to present the particles to the vacuum-driven assembly membranes. This work has been published as a cover article in Materials & Design (Van Geite et al., 2022) and in Powder Technology (Jimidar et al., 2021) and offers a new method to produce for the rapid (<1s) assembly of high quality monolayers (errors <0.1% measured over large repeat series). We also demonstrated these can subsequently be deposited onto a second surface. Unfortunately, this surface is currently limited to soft surfaces and not to the rigid surface that are needed to 3D print particle assemblies. The electrostatic particle cloud generation method produced more repeatable and flawless layers than those obtained with the wet assembly processes and the pressure-shock method (both published in Powder Technology: Berneman et al., 2020 and Van Geite et al., 2022) we initially mainly focused on.
Another major finding in the project has been the development of a method to uniformly fill an array of circular pockets with single particles. This technique has subsequently been applied to fill networks of interconnected pockets (so-called structured micro-grooves) to produce perfectly ordered particle beds for miniature-scale chromatography. This work has been reported as a cover story in Langmuir (Verloy et al., 2022) and protected by means of a European patent application.
As an unexpected result, we discovered a new method for the directed particle segregation & self-assembly of silica particles by rubbing-induced tribo-electrification on patterned surfaces (pattern of fluorocarbon coated patches). Our key finding is the fact that silica particles are tribo-charged due to the rubbing process and therefore stick on the fluorocarbon coating, while they are repelled from the silicon regions in between the fluorocarbon patches because of the opposite charge. During the rubbing, a monolayer of particles is on the fluorocarbon surfaces, thus creating an ordered array of self-assembled particle collections. Using Kelvin Probe Force Microscopy (KPFM), we could show that the rubbing process induces electric charge on the FC coated surface and particles. This work was published in Langmuir (Jimidar et al., 2020) and in Soft Matter (Jimidar et al., 2020).
The developed particle assembly method creating large area 2D-arrays (4 mm2 has been demonstrated but it is believed much larger areas can be addressed) using a vacuum-driven assembly process taking less than 1s is believed to be a significant improvement over the current state of the art (manual rubbing over structured elastomeric materials), both in terms of speed and automation possibilities. In a next step, methods need to be developed to stack the assembled layers on top of each other, thus opening the road to the 3D-printing of mesoscale ordered particle structures.
With the newly developed method to produce particle-filled structured micro-groove columns, ready to be tested under flow conditions, we are on the verge of being able to produce the first perfectly ordered chromatographic packed bed column. Given the expected superior separation efficiency and flow resistance characteristics, it is believed this concept will revolutionize the way chromatographic separations are being conducted.
With the newly developed method to produce particle-filled structured micro-groove columns, ready to be tested under flow conditions, we are on the verge of being able to produce the first perfectly ordered chromatographic packed bed column. Given the expected superior separation efficiency and flow resistance characteristics, it is believed this concept will revolutionize the way chromatographic separations are being conducted.