RESEARCH ARTICLE PHYSICS
Topology and kinetic pathways of colloidosome assembly
and disassembly
Raymond Adkins
a,b
ID
, Joanna Robaszewski
a,c
, Seungwoo Shin
a
ID
, Fridtjof Brauns
d
ID
, Leroy Jia
e
, Ayantika Khanra
f
ID
, Prerna Sharma
f,g
ID
,
Robert A. Pelcovits
h
ID
, Thomas R. Powers
h,i
ID
, and Zvonimir Dogic
a,1
ID
Affiliations are included on p. 7.
Edited by Noel Clark, University of Colorado Boulder, Boulder, CO; received January 16, 2025; accepted July 16, 2025
Closed capsules, such as lipid vesicles, soap bubbles, and emulsion droplets, are
ubiquitous throughout biology, engineered matter, and everyday life. Their creation
and disintegration are defined by a singularity that separates a topologically distinct
extended liquid film from a boundary-free closed shell. Such topology-changing
processes are of fundamental interest. They are also essential for intercellular transport,
transcellular communication, and drug delivery. However, studies of vesicle formation
are challenging because of the rapid dynamics and small length scale involved.
We develop fluid colloidosomes, micrometer-sized analogues of lipid vesicles. The
mechanics of colloidosomes and lipid vesicles are described by the same theoretical
model. We study colloidosomes close to their disk-to-sphere topological transition.
Intrinsic colloidal length and time scales slow down the dynamics to reveal colloidosome
conformations in real time during their assembly and disassembly. Remarkably, the
lowest-energy pathway by which a closed vesicle transforms into a flat disk involves
a topologically distinct cylinder-like intermediate. These results reveal aspects of
topological changes that are relevant to all liquid capsules. They also provide a robust
platform for the encapsulation, transport, and delivery of nanosized cargoes.
vesicles | topological transformations | shape morphing | kinetic pathways
Controlling the shape and topology of thin elastic sheets is essential for creating
reconfigurable and adaptable materials. For inspiration, one can turn toward living
matter, where shape morphing enables diverse life-sustaining processes. On macroscopic
scales, plants grow sheet-like tissues into intricate leaves and flowers that reconfigure
in response to sunlight (1, 2). At the mesoscopic scale, micrometer-thick epithelial
sheets undergo highly choreographed morphological and topological transitions to
assume complex shapes that define three-dimensional organs (3, 4). At subcellular scales,
nanometer-thick lipid bilayers are a distinct category of thin sheets that lack in-plane shear
modulus but form complex shapes and topologies (5–9). Translating these structures into
the realm of synthetic materials represents a challenge but also a unique opportunity to
generate new categories of responsive soft materials. For example, patterning in-plane
strains into mesoscale stimuli-responsive solid-elastomeric sheets generated designable
and controllable three-dimensional shape morphing materials (10–13). On microscopic
scales, lipid vesicles inspired the creation of synthetic analogues with potential applications
in transport, encapsulation, and drug delivery (14–19).
We seek to control the morphology and topology of fluid membranes by balancing
the bending and edge energy. The edge energy of a flat disk increases with its size,
while the bending energy of the edgeless spherical vesicles is size independent (20–
23). Thus, with increasing size, the edge energy destabilizes a flat disk, inducing a
mechanical instability that generates edgeless vesicles. To study such transitions, we
develop fluid colloidosomes, which are colloidal analogs of lipid vesicles, assembled from
monodisperse submicrometer-long rod-like particles. By modulating colloidosome size
in situ, we balance the edge and bending energy to control transitions between vesicle-like
spheres and disks in real-time. In particular, we elucidate the complex vesicle disassembly
pathways involving intermediate states, whose topologies are more complex than both
the initial and the final state. The rich energy landscape associated with the vesicle-to-disk
transition provides a unique platform for controlling the morphology and topology of
fluid membranes. Colloidosomes combine desirable features of fluid bilayers, including
reconfigurability, self-healing, and topological transitions, with those of solid elastic
sheets, such as programmability and control. They may also provide insight into assembly
and disassembly pathways relevant to diverse categories of closed vesicle-like materials.
Significance
Lipid membranes are
nanometer-thin soap-like films
composed of molecules with
hydrophilic and hydrophobic
segments. To minimize their edge
energy, lipid membranes form
closed spherical shells or vesicles,
ubiquitous and versatile
structures in cells with
applications in encapsulation,
molecular transport, and drug
delivery. Controlling vesicle
topology is essential in these
processes. Rapid dynamics and
small scales make it challenging
to study the topological
transitions of lipid vesicles. We
developed fluid colloidosomes,
which are micrometer-sized
analogs of lipid vesicles
assembled from rod-like
particles. Their unique features
enable real-time visualization of
colloidosome assembly and
disassembly pathways.
Intriguingly, closed vesicles
transition to flat disks via an
intermediate state that is
topologically distinct from the
initial and final states.
Author contributions: R.A., J.R., A.K., P.S., R.A.P., T.R.P., and
Z.D. designed research; R.A., J.R., S.S., F.B., L.J., and A.K.
performed research; R.A., J.R., F.B., L.J., and A.K. analyzed
data; and R.A., F.B., and Z.D. wrote the paper.
The authors declare no competing interest.
This article is a PNAS Direct Submission.
Copyright © 2025 the Author(s). Published by PNAS.
This article is distributed under Creative Commons
Attribution-NonCommercial-NoDerivatives License 4.0
(CC BY-NC-ND).
1
To whom correspondence may be addressed. Email:
zdogic@ucsb.edu.
This article contains supporting information online
at https://www.pnas.org/lookup/suppl/doi:10.1073/pnas.
2427024122/-/DCSupplemental.
Published September 4, 2025.
PNAS 2025 Vol. 122 No. 36 e2427024122 https://doi.org/10.1073/pnas.2427024122 1 of 8
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