16 research outputs found
Calculating the motion of highly confined, arbitrary-shaped particles in Hele-Shaw channels
We combine theory, numerical calculations, and experiments to accurately
predict the motion of anisotropic particles in shallow microfluidic channels,
in which the particles are strongly confined in the vertical direction. We
formulate an effective quasi-two-dimensional description of the Stokes flow
around the particle via the Brinkman equation, which can be solved in a time
that is two orders of magnitude faster than the three-dimensional problem. The
computational speedup enables us to calculate the full trajectories of
particles in the channel. To test our scheme, we study the motion of
dumbbell-shaped particles that are produced in a microfluidic channel using
`continuous flow lithography'. Contrary to what was reported in earlier work
(Uspal et al., Nature communications 4 (2013)), we find that the reorientation
time of a dumbbell particle in an external flow exhibits a minimum as a
function of its disk size ratio. This finding is in excellent agreement with
new experiments, thus confirming the predictive power of our scheme.Comment: 18 pages, 5 figures, 4 supplemental movie
Rational design and dynamics of self-propelled colloidal bead chains: from rotators to flagella
The quest for designing new self-propelled colloids is fuelled by the demand
for simple experimental models to study the collective behaviour of their more
complex natural counterparts. Most synthetic self-propelled particles move by
converting the input energy into translational motion. In this work we address
the question if simple self-propelled spheres can assemble into more complex
structures that exhibit rotational motion, possibly coupled with translational
motion as in flagella. We exploit a combination of induced dipolar interactions
and a bonding step to create permanent linear bead chains, composed of
self-propelled Janus spheres, with a well-controlled internal structure. Next,
we study how flexibility between individual swimmers in a chain can affect its
swimming behaviour. Permanent rigid chains showed only active rotational or
spinning motion, whereas longer semi-flexible chains showed both translational
and rotational motion resembling flagella like-motion, in the presence of the
fuel. Moreover, we are able to reproduce our experimental results using
numerical calculations with a minimal model, which includes full hydrodynamic
interactions with the fluid. Our method is general and opens a new way to
design novel self-propelled colloids with complex swimming behaviours, using
different complex starting building blocks in combination with the flexibility
between them.Comment: 27 pages, 10 figure
Universal motion of mirror-symmetric microparticles in confined Stokes flow
Comprehensive understanding of particle motion in microfluidic devices is
essential to unlock novel technologies for shape-based separation and sorting
of microparticles like microplastics, cells and crystal polymorphs. Such
particles interact hydrodynamically with confining surfaces, thus altering
their trajectories. These hydrodynamic interactions are shape-dependent and can
be tuned to guide a particle along a specific path. We produce strongly
confined particles with various shapes in a shallow microfluidic channel via
stop flow lithography. Regardless of their exact shape, particles with a single
mirror plane have identical modes of motion: in-plane rotation and cross-stream
translation along a bell-shaped path. Each mode has a characteristic time,
determined by particle geometry. Furthermore, each particle trajectory can be
scaled by its respective characteristic times onto two master curves. We
propose minimalistic relations linking these timescales to particle shape.
Together these master curves yield a trajectory universal to particles with a
single mirror plane.Comment: 10 pages, 4 figures, 1 table, 1 PDF file containing Supplementary
Text, Figures and Tabl
Steering particles by breaking symmetries
We derive general equations of motions for highly-confined particles that perform quasi-two-dimensional motion in Hele-Shaw channels, which we solve analytically, aiming to derive design principles for self-steering particles. Based on symmetry properties of a particle, its equations of motion can be simplified, where we retrieve an earlier-known equation of motion for the orientation of dimer particles consisting of disks (Uspal et al 2013 Nat. Commun. 4), but now in full generality. Subsequently, these solutions are compared with particle trajectories that are obtained numerically. For mirror-symmetric particles, excellent agreement between the analytical and numerical solutions is found. For particles lacking mirror symmetry, the analytic solutions provide means to classify the motion based on particle geometry, while we find that taking the side-wall interactions into account is important to accurately describe the trajectories
Barriers and Best Practices for the Circular Economy
Introduction
Weâre living in an exciting era. Rather than just another societal transition, weâre going
through a fundamental societal transformation. Ecologist Joanne Macy calls this period âThe
Great Turningâ: a period wherein we change from an industrial growth society into a life
sustaining systemâ. Macy: âThe most remarkable feature of this historical moment on Earth
is not that we are on the way to destroying the world; we've actually been on the way for
quite a while. It is that we are beginning to wake up, as from a millennia-long sleep, to a
whole new relationship to our world, to ourselves and each other.â It is with these eyes that
we have to see the rise of the Circular Economy. The Circular Economy is not just another
trend in business; itâs the start of a completely new economic reality. The Circular Economy
is the starting point for regenerative economics; for a new business-as-usual that - first and
foremost - serves life and is based upon a fundamentally new value-paradigm. The future of
success in business is about doing good for all stakeholders and creating benefit; not just
profit.
The Circular Economy demands next level thinking-and-doing in business, and there is no
one more willing and able than the next generation of young professionals. It is therefore
with great pride and pleasure that I present to you this publication of the SMO Promovendi.
It offers fresh perspectives of a group of promising young scientists. All aspiring
changemakers. Itâs made with love and with the best of intentions; to help the Circular
Economy forward
Steering particles by breaking symmetries
We derive general equations of motions for highly-confined particles that perform quasi-two-dimensional motion in Hele-Shaw channels, which we solve analytically, aiming to derive design principles for self-steering particles. Based on symmetry properties of a particle, its equations of motion can be simplified, where we retrieve an earlier-known equation of motion for the orientation of dimer particles consisting of disks (Uspal et al 2013 Nat. Commun. 4), but now in full generality. Subsequently, these solutions are compared with particle trajectories that are obtained numerically. For mirror-symmetric particles, excellent agreement between the analytical and numerical solutions is found. For particles lacking mirror symmetry, the analytic solutions provide means to classify the motion based on particle geometry, while we find that taking the side-wall interactions into account is important to accurately describe the trajectories.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Intensified Reaction and Separation System
Steering particles by breaking symmetries
We derive general equations of motions for highly-confined particles that perform quasi-two-dimensional motion in Hele-Shaw channels, which we solve analytically, aiming to derive design principles for self-steering particles. Based on symmetry properties of a particle, its equations of motion can be simplified, where we retrieve an earlier-known equation of motion for the orientation of dimer particles consisting of disks (Uspal et al 2013 Nat. Commun. 4), but now in full generality. Subsequently, these solutions are compared with particle trajectories that are obtained numerically. For mirror-symmetric particles, excellent agreement between the analytical and numerical solutions is found. For particles lacking mirror symmetry, the analytic solutions provide means to classify the motion based on particle geometry, while we find that taking the side-wall interactions into account is important to accurately describe the trajectories.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Intensified Reaction and Separation System
Universal motion of mirror-symmetric microparticles in confined Stokes flow
Comprehensive understanding of particle motion in microfluidic devices is essential to unlock additional technologies for shape-based separation and sorting of microparticles like microplastics, cells, and crystal polymorphs. Such particles interact hydrodynamically with confining surfaces, thus altering their trajectories. These hydrodynamic interactions are shape dependent and can be tuned to guide a particle along a specific path. We produce strongly confined particles with various shapes in a shallow microfluidic channel via stop flow lithography. Regardless of their exact shape, particles with a single mirror plane have identical modes of motion: in-plane rotation and cross-stream translation along a bell-shaped path. Each mode has a characteristic time, determined by particle geometry. Furthermore, each particle trajectory can be scaled by its respective characteristic times onto two master curves. We propose minimalistic relations linking these timescales to particle shape. Together these master curves yield a trajectory universal to particles with a single mirror plane
Steering particles by breaking symmetries
We derive general equations of motions for highly-confined particles that perform quasi-two-dimensional motion in Hele-Shaw channels, which we solve analytically, aiming to derive design principles for self-steering particles. Based on symmetry properties of a particle, its equations of motion can be simplified, where we retrieve an earlier-known equation of motion for the orientation of dimer particles consisting of disks (Uspal et al 2013 Nat. Commun. 4), but now in full generality. Subsequently, these solutions are compared with particle trajectories that are obtained numerically. For mirror-symmetric particles, excellent agreement between the analytical and numerical solutions is found. For particles lacking mirror symmetry, the analytic solutions provide means to classify the motion based on particle geometry, while we find that taking the side-wall interactions into account is important to accurately describe the trajectories