ZnO nanowire array growth on precisely controlled patterns of inkjet-printed zinc acetate at low-temperatures

ZnO nanowires have been fabricated through the hydrothermal method on inkjet-printed patterns of zinc acetate dihydrate. The silicon substrate used was heated accordingly during the printing period in order to maintain good spatial uniformity of the zinc acetate nanoparticles, responsible for the pattern morphology. Printing more than one pass of precursor ink leads to an increase in seed layer thickness that subsequently alters the density and dimensions of nanowires. It has been demonstrated that with the right inkjet-printing parameters and substrate temperature, ZnO nanowires can be effortlessly fabricated in accordance with the desired pattern variations under low temperature and mild conditions that ensures promising applications in optoelectronic devices

Ultralow-Power All-Inkjet-Printed Organic Thin-Film Transistors for Wearables

Wearable electronics requires devices to have low power consumption at the same time high signal amplification capability. However, traditional device technologies do not fulfill all of these requirements. This work presents novel organic thin-film transistors (OTFT) fabricated all by an inkjet printing technology, greatly reducing fabrication cost. Devices with a Schottky barrier at the source-semiconductor contact and subthreshold operation exhibit ultralow-power ( 1000\V/V), along with good uniformity as compared to other transistor technologies. In addition, we show that by reducing device interface trap density, the subthreshold slope of the fabricated OTFTs can almost reach the thermionic limit of 60 mV/decade, with a shelf life as long as 6 months. To demonstrate its potential deployment in wearables, we present device fabrication on plastic strips so that the OTFTs can be weaved in a smart fabric and/or embedded into a stretchable fiber

Computational modelling and characterisation of nanoparticle-based tuneable photonic crystal sensors

Photonic crystals are materials that are used to control or manipulate the propagation of light through a medium for a desired application. Common fabrication methods to prepare photonic crystals are both costly and intricate. However, through a cost-effective laser-induced photochemical patterning, one-dimensional responsive and tuneable photonic crystals can easily be fabricated. These structures act as optical transducers and respond to external stimuli. These photonic crystals are generally made of a responsive hydrogel that can host metallic nanoparticles in the form of arrays. The hydrogel-based photonic crystal has the capability to alter its periodicity in situ but also recover its initial geometrical dimensions, thereby rendering it fully reversible and reusable. Such responsive photonic crystals have applications in various responsive and tuneable optical devices. In this study, we fabricated a pH-sensitive photonic crystal sensor through photochemical patterning and demonstrated computational simulations of the sensor through a finite element modelling technique in order to analyse its optical properties on varying the pattern and characteristics of the nanoparticle arrays within the responsive hydrogel matrix. Both simulations and experimental results show the wavelength tuneability of the sensor with good agreement. Various factors, including nanoparticle size and distribution within the hydrogel-based responsive matrices that directly affect the performance of the sensors, are also studied computationally. © 2014 The Royal Society of Chemistry