Printed Dual Cell Arrays for Multiplexed Sensing.

We demonstrated inkjet printing of large-scale dual-type encapsulated bacterial cell arrays for prospective multiplexing sensing. The dual cell arrays were constructed on the basis of two types of bioengineered cells hosting fluorescent reporters (green-GFPa1 and red-turboRFP) capable of detecting different target chemicals. The versatility of inkjet printing allows for the fabrication of uniform multilayered confined structures composed of silk ionomers that served as nests for in-printing different cells.

Inkjet printing of silk nest arrays for cell hosting.

An inkjet printing approach is presented for the facile fabrication of microscopic arrays of biocompatible silk "nests" capable of hosting live cells for prospective biosensors. The patterning of silk fibroin nests were constructed by the layer-by-layer (LbL) assembly of silk polyelectrolytes chemically modified with poly-(l-lysine) and poly-(l-glutamic acid) side chains. The inkjet-printed silk circular regions with a characteristic "nest" shape had diameters of 70-100 μm and a thickness several hundred nanometers were stabilized by ionic pairing and by the formation of the silk II crystalline secondary structure.

Inkjet-assisted layer-by-layer printing of encapsulated arrays.

We present the facile fabrication of hydrogen-bonded layer-by-layer (LbL) microscopic dot arrays with encapsulated dye compounds. We demonstrate patterned encapsulation of Rhodamine dye as a model compound within poly(vinylpyrrolidone)/poly(methacrylic acid) (PVPON/PMAA) LbL dots constructed without an intermediate washing step. The inkjet printing technique improves encapsulation efficiency, reduces processing time, facilitates complex patterning, and controls lateral and vertical dimensions with diameters ranging from 130 to 35 μm (mostly controlled by the droplet size and the substrate hydrophobicity) and thickness of several hundred nanometers.

Gold nanoparticles grown on star-shaped block copolymer monolayers.

We report on the growth of gold nanoparticles in polystyrene/poly(2-vinyl pyridine) (PS/P2VP) star-shaped block copolymer monolayers. These amphiphilic PS(n)P2VP(n) heteroarm star copolymers differ in molecular weight (149,000 and 529,000 Da) and the number of arms (9 and 28). Langmuir-Blodgett (LB) deposition was utilized to control the spatial arrangement of P2VP arms and their ability to reduce gold nanoparticles.

pH-controlled exponential and linear growing modes of layer-by-layer assemblies of star polyelectrolytes.

We report the unique layer-by-layer (LbL) assembly behavior of pH-sensitive star-shaped polyelectrolytes with both linear and exponential growth modes controlled by star architecture and assembly conditions. Cationic poly[2-(dimethylamino)ethyl methacrylate] and anionic poly(acrylic acid) stars were synthesized via "core-first" atom-transfer radical polymerization (ATRP) based on multifunctional initiators, in addition to their linear analogues. We demonstrated the LbL growth behavior as a function of deposition pH (ranging from 5 to 7), number of layers (up to 30 bilayers), and the method of assembly (dip- vs spin-assisted LbL).