Additive manufacturing at the micro‐ and nanoscale has seen a recent upsurge to suit an increasing demand for more elaborate structures. However, the integration of multiple distinct materials at small scales remains challenging. To this end, capillarity‐assisted particle assembly (CAPA) and two‐photon polymerization direct laser writing (2PP‐DLW) are combined to realize a new class of multimaterial microstructures. 2PP‐DLW and CAPA both are used to fabricate 3D templates to guide the CAPA of soft‐ and hard colloids, and to link well‐defined arrangements of functional microparticle arrays produced by CAPA, a process that is termed “printing on particles.” The printing process uses automated particle recognition algorithms to connect colloids into 1D, 2D, and 3D tailored structures, via rigid, soft, or responsive polymer links. Once printed and developed, the structures can be easily re‐dispersed in water. Particle clusters and lattices of varying symmetry and composition are reported, together with thermoresponsive microactuators, and magnetically driven “micromachines”, which can efficiently move, capture, and release DNA‐coated particles in solution. The flexibility of this method allows the combination of a wide range of functional materials into complex structures, which will boost the realization of new systems and devices for numerous fields, including microrobotics, micromanipulation, and metamaterials.
Endowing materials with the ability to sense, adapt, and respond to stimuli holds the key to a progress leap in autonomous systems. In spite of the growing success of macroscopic soft robotic devices, transferring these concepts to the microscale presents several challenges connected to the lack of suitable fabrication and design techniques and of internal response schemes that connect the materials’ properties to the function of the active units. Here, we realize self-propelling colloidal clusters which possess a finite number of internal states, which define their motility and which are connected by reversible transitions. We produce these units via capillary assembly combining hard polystyrene colloids with two different types of thermoresponsive microgels. The clusters, actuated by spatially uniform AC electric fields, adapt their shape and dielectric properties, and consequently their propulsion, via reversible temperature-induced transitions controlled by light. The different transition temperatures for the two microgels enable three distinct dynamical states corresponding to three illumination intensity levels. The sequential reconfiguration of the microgels affects the velocity and shape of the active trajectories according to a pathway defined by tailoring the clusters’ geometry during assembly. The demonstration of these simple systems indicates an exciting route toward building more complex units with broader reconfiguration schemes and multiple responses as a step forward in the pursuit of adaptive autonomous systems at the colloidal scale.
Additive manufacturing at the micro-and nanoscale has seen a recent upsurge to suit the increasing demand for more elaborate structures. However, the integration and precise placement of multiple distinct materials at small scales remain a challenge. To this end, we combine here the directed capillary assembly of colloidal particles and two-photon direct laser writing (DLW) to realize a new class of multi-material microstructures. We use DLW both to fabricate 3D micro-templates to guide the capillary assembly of soft-and hard colloids, and to link well-defined arrangements of polystyrene or silica particles produced with capillary assembly, a process we term "printing on particles". The printing process is based on automated particle recognition algorithms and enables the user to connect colloids into one-and two-dimensional tailored structures, including particle clusters and lattices of varying symmetry and composition, using commercial photo-resists (IP-L or IP-PDMS). Once printed and developed, the structures can be easily harvested and re-dispersed in water. The flexibility of our method allows the combination of a wide range of materials into complex structures, which we envisage will boost the realization of new systems for a broad range of fields, including microrobotics, micromanipulation and metamaterials.
Nature uses replication to amplify the information necessary for the intricate structures vital for life. Despite some successes with pure nucleotide structures [1–5], constructing synthetic microscale systems capable of replication remains largely out of reach [6]. Here we show a functioning strategy for microscale replication using DNA-coated colloids. By positioning DNA-functionalized colloids through capillary assembly [7] and embedding them into a polymer layer, we create programmable sequences of patchy particles that act as a primer and offer precise binding of complementary particles from suspension. The strings of complementary colloids are crosslinked, released from the primer, and purified via flow cytometric sorting, to achieve a purity of up to 81% of replicated sequences. We demonstrate the replication of strings of up to five colloids, non-linear shapes, and using particles of different sizes and materials. Furthermore, we propose a strategy to replicate a second generation of sequences with the vision for exponential self-replication.
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