Self-Assembly of Spherical Colloidal Photonic Crystals inside Inkjet-Printed Droplets

Abstract

The manufacturing of three-dimensional colloidal structures on solid substrates is an important topic of applied research, aiming for photonic components especially in photovoltaic and sensor applications. Whereas conventional techniques such as wet self-assembly are based on engineering of the substrate surface energy, alternative strategies envisage the independence of the interfacial conditions. We report on inkjet printing of colloidal suspensions of monodisperse silica or polystyrene nanoparticles or both and their self-assembly to spherical colloidal photonic crystals. The formation process of the colloidal nanoparticles into stable spherical colloidal assemblies (SCAs) is achieved by a self-assembly process inside tiny droplets of a stochastic mist generated intentionally instead of a jet of individual single droplets using inkjet printing. The mist-jetted, shrinking droplets serve as confined geometries for the solidification of the nanoparticles during the evaporation; thus the particles are packed into stable ball-shaped assemblies. We show how fine-tuning of the jetting parameters allows the reliable generation and deposition of three-dimensional (3D) spherical colloidal assemblies of nanoparticles variable in size and with a high packing order. Microreflectance spectroscopy proves that the degree of order in the SCA is such that photonic stop bands occur inherent for photonic crystals.

Sodium dodecyl sulfate microaggregates with diversely developed surfaces: Formation from free microdroplets of colloidal suspension

“…The WSA approaches are usually based on using emulsions. The spherical aggregates are formed by the arrangement of the suspended particles inside the droplets emulsified in the liquid [12]. Well-known drawbacks associated with the WSA methods are mainly due to the necessity of demulsification processes allowing extraction of the final dry micro-or nano-products and the difficulty in controlling the shape of the final products.…”

“…Techniques employing DSA methods are often considered to be more favourable in comparison to the WSA methods [1,11,12]. The DSA methods are mostly based on approaches where droplets of colloidal suspensions are dried in spray dryers [3,9,14], on solid surfaces [1,5,7] or in Leidenfrost levitation [6].…”

Direct observation and rational design of nucleation behavior in addressable self-assembly

“…Increasingly complex structures can now be created by self-assembly ( 1 , 2 ), from nanostructures with tailored physicochemical properties, such as photonic crystals ( 3 , 4 ), to quasicrystals ( 5 – 7 ). In the limit where every subunit in a target structure is unique and bonds strongly with specific partners, such self-assembled structures are said to be “addressable.” Thus far, this degree of specificity has been demonstrated most impressively by experiments on “DNA bricks” ( 8 , 9 ), in which portions of single-stranded DNA molecules are designed to hybridize uniquely with complementary sequences on strands that occupy neighboring positions in the target structure.…”

Inkjet printed nanomaterial based flexible radio frequency identification (RFID) tag sensors for the internet of nano things

“…Different types of photonic crystals have been used for inkjet printing to create structural color patterns for applications in security and anticounterfeiting. [109][110][111][112][113] The inkjet printing of silver NP ink on exible substrates has shown great potential for printing conductive patterns for wearable electronic devices. Jiang et al 113 reported printing of silver nanoparticle (AgNP) ink on top of the patterned polymer nanostructures where the polymer nanostructures molded the printed silver and yielding into structural colors.…”