Sensors and Actuators A 164 (2010) 68–73 Contents lists available at ScienceDirect Sensors and Actuators A: Physical journal homepage: www.elsevier.com/locate/sna Fabrication and testing of cellulose EAPap actuators for haptic application Gyu-Young Yun a , Jaehwan Kim a , Joo-Hyung Kim b,∗ , Sang-Youn Kim c,∗∗ a Creative Research Center for EAPap Actuator, Department of Mechanical Engineering, INHA University, Yong-Hyun Dong 253, Nam Gu Incheon 402-751, South Korea b Laboratory of Nano-micro Devices, Department of Electronic Engineering, College of Electronics and Information Engineering, Chosun Univerisity, Seo-Seok Dong 375, Dong-Gu, Gwangju 501-759, South Korea c Interaction Laboratory, Advanced Technology Research Center, Korea University of Technology and Education, Cheonan City, Chung-Nam 330-708, South Korea article info Article history: Received 14 August 2009 Received in revised form 1 September 2010 Accepted 2 September 2010 Available online 21 September 2010 Keywords: Electro-active paper (EAPap) Piezoelectric Actuator Stacked Unimorph Haptic Resonance frequency abstract Piezoelectric behavior of the cellulose electro-active paper (EAPap) actuators is studied for a possible haptic actuator. Using a thin stretched EAPap film with a material fiber orientation of 45 ◦ , stacked and unimorph EAPap actuators are prepared and their performance is investigated as functions of frequency and applied electric field. A small actuation displacement is observed from the stacked EAPap actua- tor. The displacement of the stacked actuator is dependent on the actuation frequency. The actuation displacement and resonance frequency of the unimorph type EAPap actuators are investigated with dif- ferent beam lengths. At 1 Hz, the piezoelectric constant d 33 of the 32-layer-stacked EAPap actuator is about 150 pm/V and decreases as the operating frequency increases. A unimorph EAPap actuator with 60 mm length and 10 mm width shows a 75 m of bending displacement at 10 Hz. From the experimental study, we demonstrate the feasibility of the cellulose EAPap for haptic applications. © 2010 Elsevier B.V. All rights reserved. 1. Introduction The term of ‘haptic’ is a word which is related to touch sen- sation (kinesthetic and tactile sensation). Kinesthetic information refers to sensory data obtained through receptors of joints, mus- cles, ligaments, etc. Tactile information, which is conveyed through mechanoreceptors and thermoreceptors in skin, includes rough- ness, micro-shape, and temperature of a target object. A user recognizes the stiffness of an object through the kinesthetic infor- mation and discerns the texture of an object through the tactile information. The kinesthetic and tactile information is transmit- ted to a user via a haptic device which is a computer-controlled electro-mechanical interface. Researchers have focused on developing kinesthetic actuators which can provide force or pressure and have also concentrated their research works upon constructing kinesthetic devices with developed actuators [1–3]. However, these kinesthetic actuators are too bulky to be embedded in small-size devices, e.g. hand- held devices. Therefore, for the small-size devices, it is essential to develop tactile actuators which can stimulate human’s mechanore- ∗ Corresponding author. Tel.: +82 62 230 7063. ∗∗ Corresponding author. Tel.: +82 41 560 1484. E-mail addresses: joo-hyung.kim@chosun.ac.kr (J.-H. Kim), sykim@kut.ac.kr (S.-Y. Kim). ceptors. Tactile actuators in early stage have been focused on the development and the adaptation of eccentric vibration motors which are combined the centrifugal force by an eccentric mass and the repulsive force between a solenoid and a permanent mag- net to generate vibrotactile effect [4,5]. However, in the eccentric motor, since the vibration intensity is proportional to the square of the number of motor’s revolution, we can hardly control the fre- quency and the intensity of vibration independently. Therefore, the use of the eccentric motor limits our ability to discriminate various vibrotactile sensations. In order to generate a variety of tactile sen- sation, researchers started to turn their attention on developing new tactile actuators. Some of these endeavors have been com- mercialized [6] and published their accomplishment. One of the most popular actuators is a motor based system using a piezo- electric material whose shape can be deformed according to the amount of electric field [7–9]. Since the piezo-motor can actuate over a broad range of frequencies, these actuators can convey vari- ous tactile sensations. Although the tactile sensation by vibrotactile actuators can improve usability and immersion, the vibrotactile actuators can hardly generate a detailed texture in a small scale shape. In order to overcome the limitation, there have been many attempts to develop pin-array type tactile actuating systems which can selectively stimulate human’s mechanoreceptors. Wang et al. have developed a pin-array type tactile transducer system which generates a relatively large lateral skin deformation by adjusting the cantilever mechanics [10]. Recently Kim et al. have developed 0924-4247/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.sna.2010.09.005