Printing Techniques and Performance of Chipless Tag Design on Flexible Low-Cost Thin-Film Substrates

1. Introduction

RFID stands for Radio Frequency Identification which uses the radio frequency for communication between tags and reader through free space. A typical RFID system consists of a Reader, transponder (RFID tags) and processing unit for processing the data from the transponder as shown in Figure 1 below.

Figure 1.

Schematic of a generalized radio frequency identification system

Automatic identification procedure has become popular in this age of modern technology and is playing a vital role in recent business activities of global economy. In coping up with the fast paced lifestyle of this Century, the demand for automation is on the increase day by day. In this respect, Radio Frequency Identification (RFID) finds an ever increasing application and has only been emerging recently as a powerful alternative to conventional security technology for product authentication. RFID systems have been gaining more and more popularity in areas such as supply chain management, inventory control, automated identification systems, and any place requiring identifications of products or people. RFID technology is better than barcode in many ways (Non Line of Sight Communication, longer operating range, quick reading of tags etc.)(Preradovic & Karmakar, 2010)), and may totally replace the older ‘barcode identification system’ all together in the future, if the printing of tags on flexible low-cost substrates hits commercial success. A typical RFID (Radio Frequency Identification) system (Figure1) includes RFID tag (Transponders), reader (Interrogation Unit) and Data Processing Unit (Host Computer for necessary processing on received data to decode the Tag ID). Tags are attached to objects/persons, and readers communicate with tags in their transmission ranges via radio signals. Yang Xiao et al (Xiao et al., 2007) discussed in depth about the technologies, applications and research issues of RFID. Here it can be concluded that issues relating to the cost efficiency of RFID equipment, other issues such as energy efficiency, interference from multiple readers and security issues need further investigation.

The main hindrance to commercialization of RFID technology comes from the price of the tag which is much higher compared to the traditional barcode feature. The bulk of the cost of RFID tag comes from the silicon chip that is used to store data. Significant research and development investments are in place worldwide to replace the silicon chip with printed circuitry (printed transistors / resonating circuits) on the same substrate. The antenna is either printed together with the circuitry or separately which is then attached to the circuit with some low-cost technique (Subramanian et al., 2010). Chip-less tag does not require any chip/IC hence there is no need of a battery to turn on the chip. Such tags can be printed on low cost substrates using conventional printing technology with conductive ink for use in item level tagging and other applications. As chipless tags do not require any power supply to turn on its response, they can work with low power and even from long distances.