Colloids with high-definition surface structures

Abstract

Compared with the well equipped arsenal of surface modification methods for flat surfaces, techniques that are applicable to curved, colloidal surfaces are still in their infancy. This technological gap exists because spin-coating techniques used in traditional photolithographic processes are not applicable to the curved surfaces of spherical objects. By replacing spin-coated photoresist with a vapor-deposited, photodefinable polymer coating, we have now fabricated microstructured colloids with a wide range of surface patterns, including asymmetric and chiral surface structures, that so far were typically reserved for flat substrates. This highthroughput method can yield surface-structured colloidal particles at a rate of Ϸ10 7 to 10 8 particles per operator per day. Equipped with spatially defined binding pockets, microstructured colloids can engage in programmable interactions, which can lead to directed self-assembly. The ability to create a wide range of colloids with both simple and complex surface patterns may contribute to the genesis of previously unknown colloidal structures and may have important technological implications in a range of different applications, including photonic and phononic materials or chemical sensors.biomaterials ͉ chemical vapor deposition polymerization ͉ polymer coatings ͉ surface engineering ͉ self-assembly C omplex colloidal structures have been a major focus of fundamental and applied research because of their potential applications in photonic (1-6) or phononic (7) band gap materials, chemical sensors (8), or data storage devices (9). Many of these applications will require colloids to be organized in nontrivial colloidal crystal structures with exquisite lattice periodicity, such as the diamond lattice (10). In principle, cocrystallization of binary mixtures of oppositely charged particles can form a range of unusual colloidal crystals (11)(12)(13)(14)(15)(16)). An alternate approach relies on the use of colloids that have spatially defined binding patches to encode and ultimately direct lattice organization (10). Although the potential merits of such an approach, e.g., homogenous colloidal assemblies and potentially superior optical properties, have been widely recognized (10, 17), successful experimental implementation has been hampered by the limited availability of suitable surface modification protocols for colloidal particles (18)(19)(20)(21). This limited availability of microstructuring techniques stands in clear contrast to the sizable number of patterning processes that have been developed for flat surfaces (22, 23), contributing to major technological breakthroughs in electronics and biotechnology (24).Recently, chemical vapor deposition (CVD) polymerization, a solventless coating process, which relies on the deposition of reactive coatings made of functionalized poly-p-xylylenes, has been developed as a flexible surface modification approach (25). Reactive coatings have been used to prepare polymer films with a wide range of functional groups, such as photoreact...

Recent advances with anisotropic particles

“…Expanding the arsenal of surface modification procedures, maskless photopatterning methods [44] as well as microcontact printing has been adopted for chemical functionalization of colloids [45][46][47]. Several groups have used elastomeric stamps to transfer a range of different molecules onto the exposed surface of particles.…”

Compartmentalized Photoreactions within Compositionally Anisotropic Janus Microstructures

“…[10] Our group has recently used maskless photolithography for creation of surface patterns on colloidal particles. [17] While these processes are in principle applicable to smaller scales, the actual particles are often relatively large, and methods, such as maskless photopatterning of coated microbeads, are strictly limited to the modification of surfaces. In order to prepare Janus particles with anisotropic bulk compositions, various technical approaches have been developed so far including microfluidics, [10] solvent evaporation methods, [11] and self-assemble methods.…”

Porous polymer particles—A comprehensive guide to synthesis, characterization, functionalization and applications

“…In addition, there are directional methods that are being used to form chemical patches on surface of particles such as microcontact printing [387][388], etching [389], laser- [390] or UV-induced deposition [391], projection lithography [392], metal deposition [393][394] and temporary masking one side of particles while modifying the other [395][396]. Most of these methods are waiting to be explored for porous particles.…”