A Low-Cost Data-Glove for Human Computer Interaction Based on Ink-Jet Printed Sensors and ZigBee Networks

Nattapong Tongrod and Teerakiat Kerdcharoen

Departent of Physics, Faculty of Science, Mahidol University, Bangkok, Thailand

teerakiat@yahoo.com

Natthapol Watthanawisuth and Adisorn Tuantranont

NECTEC, Pathumthani, Thailand adisorn.tuantranont@nectec.or.th

Abstract

In this paper, a data-glove based on new kind of sensors is presented as an alternative to expensive devices. These sensors were realized using a conductive polymer (PEDOT:PSS) thin film printed on glossy photo paper. To demonstrate the printed sensors, we constructed a data glove using such sensors and developed software for real-time hand tracking. Wireless networks based on low-cost ZigBee technology were used to transfer data from the glove to a computer. This data-glove is very useful in many contexts such as telerobotics, rehabilitation and HCI applications. 1. Introduction

The glove-based input devices for HCI applications are the most popular one. There are several kinds of data-glove commercially available [1], but most of them are too expensive. In this paper, we have designed a data glove equipped with low-cost bending and pressure sensors based on printed electronics technology. These sensors were realized using a conductive polymer (PEDOT:PSS) thin film printed on glossy photo paper. To demonstrate the proposed concept, we constructed a data glove using such sensors and developed software for real-time hand tracking. Wireless networks based on low-cost ZigBee technology were used to transfer data from the glove to a computer. ZigBee is a technique based on the IEEE 802.15.4 standard that enables the communication device to operate using ultra-low power consumption [2]. Therefore, ZigBee technology is very appropriate for implementation of a low-cost network where a large number of data gloves can be connected simultaneously.

2. System hardware overview

Figure 1. The data glove for real-time hand tracking.

In this paper, we have designed a data glove for

tracking of finger bending and fingertip pressing. The data glove is equipped with bending sensors, pressure sensors and a ZigBee transmitter module for acquiring and transmitting data from these sensors to ZigBee receiver module that connect to a computer. A bending sensor was positioned on the back of each finger joint of the data glove with a pressure sensor attached to the front side of each fingertip. 2.1. Sensor design and fabrication

In this paper, we adopted the concept of surface resistance and surface current to design the sensor patterns. The relationship between surface current and surface area of sensor is

SI ∝ S [3]. Therefore, if the surface area of the sensor ( S ) is increased, the surface current (

SI ) will increase and the surface resistance will decrease.

2.2. Sensor test 2.2.1. Resistance test. The relationship between the number of repeating printed layers versus the sensor

resistance of bending sensor patterns and pressure sensor patterns is plotted in Figure 2.

Figure 2. The relationship between the numbers of printed layers and device

resistance of bending and pressure sensor patterns.

2.2.2. Bending test. In the bending testing, the sensors were subjected to angular deformation in the range of 0-60°, with a constant step of 10° and a holding time of 10 sec. The process was repeated for three times and the resistive response was measured.

Figure 3 The average sensor response and its standard deviation versus bending angles.

2.2.3. Pressure test. In the test, we used digital force gauge to apply load on the sensor. The sensors were loaded on top by a preset force of 56.50 Kpa. with a holding time of 10 sec. The process was repeated for three times and the resistive response to pressure was measured.

Pressure sensor time response (The sensor response to loading by a preset force of 56.50 Kpa.)

0

0.2

0.4

0.6

0.8

1 5 9 13 17 21 25 29 33 37 41 45 49 53 57 61Time (Sec)

%(d

R/R

)

Pressure Sensor (Layer 20)

Figure 4. Pressure sensor time response. 3. Hand tracking software

We used Microsoft visual C# to develop a hand tracking software. This program consists of finger bend identification and fingertip pressure identification. Although the bending sensors are able to detect the bent fingers with a definite step in the range 0° to 60°, only two characteristics were taken into account: straight (0°) and complete bending (more than 60°). Therefore, values in between will be round off in the preliminary version of this data glove. For the fingertip pressure identification, this preliminary version allows only two states (yes or no) to be identified. 4. Conclusions

In this paper, all-printed polymeric sensors have been realized using PEDOT:PSS based on consumer ink-jet printing technology. Performance of these sensors can be enhanced by optimizing the resistance through a design process such as pattern selection and number of repetitive printing. For the bending test, we have reproducibly obtained a nearly linear response (for bending angle > 20°) during a set of repeated measurements. For the pressure test, the sensors show a good recovery. These sensors were integrated with ZigBee wireless network device into a data glove to demonstrate the hand tracking application. In this paper, we have constructed and tested only one data glove. In fact, the ZigBee technology allows a large number of data gloves to communicate in the network. The low cost implementation of both sensors and communication network as proposed in this paper should pave the way toward a widespread implementation of data glove for Human-computer interaction.

5. References [1] M. Sama, V. Pacella, E. Farella, L. Benini and B. Ricco, “3dID: a low-power, low-cost hand motion capture device”, Proc. IEEE, Int. Conf. Design Automation and Test in Europe, 2006, pp. 136-141. [2] R. Morais, M. A. Fernandes, S. G. Matos, C. Serodio, P.J.S.G. Ferreira and M.J.C.S. Reis, “A ZigBee multi-powered wireless acquisition device for remote sensing applications in precision viticulture”, Comput. Electron. Agr., 2008, 62, pp. 94-106. [3] W.A. Maryniak, T. Uehara, M.A. Noras, “Surface Resistivity and Surface Resistance Measurements Using a Concentric Ring Probe Technique”, Trek Application Note, 2003, 1005, pp. 1-4.

Bending Sensor (Layer 20)