Nauman Malik Muhammad

Fine-resolution patterning of copper nanoparticles through electrohydrodynamic jet printing

This paper presents the low-cost, fine-resolution printing of conductive copper patterns on silicon substrate. The colloidal solution containing copper nanoparticles is deposited through electrohydrodynamic printing technology. Conductive copper tracks of different width are printed by varying the operating conditions (applied voltage and flow rate) and controlling the jet diameter. The minimum pattern width achieved was approximately 12 ?m with the average thickness of 82 nm across the width after the sintering process. The achieved pattern width is five times smaller than the capillary used for patterning. The morphology and purity of the printed copper tracks were analyzed through scanning electron microscopy (SEM), atomic force microscopy (AFM) and x-ray diffraction (XRD). The current?voltage (I?V) characteristic of the printed copper tracks showed linear Ohmic behavior and exhibited resistivity ranging from 5.98???10?8?? m?1?to 2.42???10?7?? m?1.

Hybrid piezo-electrostatic inkjet head for printed electronics:

Even after the successful demonstration of the electrostatic printing method for the generation of the printed conductive lines, it has not been commercialized until now for printed electronics fabrication. This is mainly because of the application of high voltage for the ejection of the droplet being reported and high throughput. In the study presented in this article, a novel hybrid piezoelectric and electrostatic device is proposed for reducing energy requirements of the electrostatic inkjet head with the help of a pre-developed meniscus through piezoelectric actuation. In the proposed concept, the meniscus is generated at the tip of the electrode and the electrostatic potential applied which has its highest gradient at the electrode apex. Two different arrangements of piezo-actuator installation in the inkjet printing head are analysed. Furthermore, the numerical simulations have been performed to compare the drop size for pre-developed meniscus and electrostatically developed meniscus and cone-jet for the ejection of the drop. It is demonstrated that this approach reduces the size of the droplet considerably and also reduces the electrostatic potential for droplet generation.

Electrospray deposition of thin copper-indium-diselenide films

Abstract Electrospray deposition is fast finding application in the field of thin film device manufacturing processes. The ease and cost efficiency attached to electrospray deposition with possible integration with roll-to-roll fabrication lines is the potential future of thin film device manufacturing. In this study thin films composed of copper-indium-diselenide, more commonly known as CIS, have been made using the electrospray deposition of nano-particle based inks for the ultimate manufacture of CIS-based solar cells. It is the first time that a complete CIS layer has been deposited through electrospray in a single step without involving any other process. Deposited layers are thoroughly characterized using techniques such as scanning electron microscope, X-ray diffraction and X-ray photoelectron spectroscopy. Moderate voltage requirements, dense, large grained, ∼1 μm thick layers and reasonable sintering temperatures involved in the electrospray deposition process promise the possible applicability of electrospray deposition in the manufacturing of cheap and easy to build solar cells.

Electrohydrodynamic Inkjet – Micro Pattern Fabrication for Printed Electronics Applications

In electronic industry the manufacturing of conductive patterning is necessary and ineluctable. Traditionally, lithography is widely used for fabrication of the conductive patterns. However, lithographic processes require the complicated equipments, are time consuming and the area throughput is limited. In order to reduce the material usage, process time and large area fabrication, different fabrication technique is required. Nonlithographic-direct fabrication method (Pique & Chrisey, 2001) such as inkjet (Gans et al., 2004) and roll-to-roll (Gamota et al., 2004) printing (also known as printed electronics) are predominant examples for reasonable resolution and high throughput as compared to lithography techniques. This direct fabrication technology can be further classified into two different technologies depending on the fabrication method as contact (gravure, offset or flexographic etc) and non-contact (inkjet) method. Non-contact inkjet printing method has moved beyond graphic printing as a versatile manufacturing method for functional and structural materials. Commercially available inkjet printer can be divided into two modes based on the ejection of the fluid: Continuous, where jet emerges from the nozzle which breaks in stream of droplets or Drop-on-Demand, the droplet ejects from the nozzle orifice as required (Lee, 2002). Inkjet printing offers the advantages of low cost, large area throughput and high speed processing. The most prominent examples of inkjet printing includes the direct patterning of, printed circuit board, conductive tracks for antenna of radio frequency identification tags (RFID) (Yang et al., 2007), Photovoltaic (Jung et al., 2010), thin film transistors (Arias et al., 2004), micro arrays of the DNA (Goldmann & Gonzalez, 2000), biosensors, etc. In case of continuous inkjet printing, the deflector directs the stream of droplets into a waste collector or onto substrate, for start and stop of the printing. This wastage of the ink issue has been addressed by the introduction drop-on-demand inkjet printing (thermal and piezoelectric). In drop-on-demand, thermal or vibration pulse are used to eject the liquid droplet from the nozzle to the substrate. However, the current printing technologies have constrained due to limitation of the ink viscosity, clogging of small size nozzles, generation of pattern smaller than the nozzle size and limitation of material to be deposited (Le, 1998). In order address these limitations, many researchers are focusing on electrohydrodynamic inkjet printing (continuous and drop-on-demand) (Park et al., 2007). Electrohydrodynamic jet printing uses electric field energy to eject the liquid from