Microfluidic devices with a free-standing structure were printed directly on polymer films using the functional materials that form interconnected pores. The printed devices can transport fluids by capillary action in the same fashion as paper-based microfluidic devices, and they can handle much smaller sample volumes than typical paper-based devices. Detection of glucose was performed using both colorimetric and electrochemical methods, and the observed limits of detection (LOD) were similar to those obtained with paper-based microfluidic devices under comparable testing conditions. It is demonstrated that printed microfluidic devices can be fabricated using printing processes that are suitable for high-volume and low-cost production and that the integration of microfluidic channels with electrodes is straightforward with printing. Several materials that are printable and form interconnected pores are presented.

The synthesis of 4,4'-difluoro-2,2'-bithiophene is reported and an alternating donor-acceptor copolymer of this moiety and diketopyrrolopyrrole has been prepared. This polymer has a lower highest occupied molecular orbital than its non-fluorinated analogue polymer. Organic thin film transistors based on this polymer showed p-type charge transport behavior and a hole mobility of 0.21 cm(2) V-1 s(-1) in bottom-gate bottom-contact devices. Organic solar cells using this polymer as donor and [6,6]-Phenyl-C-71-butyric acid methyl ester as acceptor achieved a power conversion efficiency of 3.4% with a high fill factor of 69%. Our morphology analysis showed that there was a lack of long-range ordered structure in the neat polymer thin film, which could cause the inferior device performance.

Due to the exponential growth of electronic textiles, the development of low cost stretchable conductive yarns has become increasingly crucial. In this study, a low cost stretchable conductive yarn is being developed by directly coating the stretchable yarns with a stretchable conductive ink. Some of the preliminary results on the stretchability of the conductive yarns being developed are reported in this paper.

The performance of printed radio frequency identification (RFID) antennas is highly dependent on the electrical conductivity of the conducting tracks forming the antennas. In this paper, screen printed high frequency (HF) RFID antennas on polyethylene terephthalate (PET) film are reported, with the focus on the optimization of the post-processing procedures for the improvement of the conductivity of the screen printed conductive tracks. The electrical conductivity of the printed conductive tracks is significantly affected by the ink post printing processing conditions. The results show that drying the ink at ambient temperature, followed by heat treatment provides the optimum conductivity. This treatment also offers the highest quality factors for the screen printed HF RFID antennas. It was also found that pre-drying at 60 °C followed by heat treatment achieves similar results with less processing time. The findings provide a low cost solution for screen printing high performance HF RFID antennas on plastic films.

High frequency (HF) radio frequency identification (RFID) loop antennas are popular for HF RFID, energy transfer and near field communication applications. One of the major parameters defining the working range of HF RFID antennas is their Q-factor. Printing techniques are the ideal method for mass fabrication of HF RFID loop antennas. However, due to the relatively low conductivity of the inks available on the market, the Q-factor of the printed HF loop antenna tends to be low and in many cases, fails to meet the working range requirements. This paper reports two methods to condense the microstructures of the conductors in order to improve the Q-factors of printed HF RFID loop antennas. Both thermal compression (pressing the sample at elevated temperature) and near-infrared annealing are studied, and the results have demonstrated that both approaches are efficient in improving the Q-factors of printed loop antennas.

Printed humidity sensors on flexible substrates has potential to be low cost platform. A novel capacitance-humidity sensor was screen printed with silver electrodes and cellulose acetate butyrate (CAB) as the dielectric on flexible polyethylene terephthalate (PET) substrate. The parallel plate design achieves capacitance between 400-500pF at ambient conditions. This study found that the sensor exhibits superior linearity from 10-70% RH with R-2 of 0.9975, and acceptable linearity between 10-85% with R2 of 0.9779 with <10s response times.

Automation of retail industry is calling for the low cost solution due to its sheer size and varied needs. Printed electronics offers a great potential in addressing the needs in point-of-sales, inventory management and self-service, in particular the radio frequency identification (RFID) systems consisting of the printed components. Screen printed Ultra high frequency (UHF) RFID reader antennas have been investigated in this work for their application potentials in retails for achieving easy-implementation and low cost. The results obtained clearly demonstrated that the screen printed UHF RFID reader antennas are closely matching the performance of their circularly polarized patch antenna counterparts fabricated using the conventional chemical etching method in most critical specifications. The screen printed antennas have been explored for the monitoring of items on metal shelves targeting potential inventory management and point-of-sales applications. It has been found that all tagged items can be identified using a home developed UHF RFID system consisting of the printed antennas. The findings pave the way for the use of low cost printed antennas in the potential retail automation applications.

Screen printed silver conductive tracks have been used or are being explored for applications in membrane switches, solar cells, radio frequency identification (RFID) antennas, diabetic testing strips, sensors etc. For many of these applications, optimizing the electric conductivity of the printed tracks is crucial. It has been noticed that the electric conductivity of the printed conductive tracks are highly dependent on the post-processing conditions. However, the understanding of the effect is limited. In this paper, preliminary study results show that ambient temperature drying followed by heat treatment offers the lowest resistance (highest conductance) for printed conductive tracks.

We report the development of inkjet-printed organic thin-film transistors (OTFTs), inverters and logic circuits on PET substrate. The mobility of 1 cm2/Vs and 0.1 cm2/Vs achieved on p-type and n-type printed OTFTs with an operation voltage of 15 V. The printed uniform and thin dielectric layer achieved by introducing coffee ring effect on printing process. A gain value of 24 obtained from the printed CMOS inverter and the device exhibits an excellent air-stability without encapsulation. Our results demonstrated the potential of the developed printed transistors for flexible electronics in the near future.

A direct-writing fabrication process for fully inkjet-printed short-channel organic thin-film transistors (OTFTs) has been developed. Channels as narrow as 800 nm between two printed Ag electrodes were achieved by printing a special Ag ink on an SU-8 interlayer, which can be partially dissolved by the solvents used in the Ag ink. The ridge formed along the printed Ag line edges due to redistribution of the interlayer material during the drying process limits the ink spread, and separates neighboring printed lines, and is the key to defining an ultra-narrow channel for transistor fabrication. The short-channel OTFTs fabricated using this technique have demonstrated well-defined linear and saturation regimes. An extracted mobility of 0.27 cm(2)/Vs with an on/off ratio of 10(5) was obtained at a driving voltage of -12 V. The excellent performance of these devices demonstrates the potential of this technique in fabrication of short-channel devices using standard printing technologies.

'Screen printing is a low cost and highly efficient printing technology. Its application to the fabrication of RF antennas is introduced in this study. Applications of screen printed antennas for RFID, frequency selective surfaces and energy harvesting applications are presented.