Design of a tactile display based on a high power CMUT array. Vasilios G. Chouvardas 1 , Amalia N. Miliou 2 Department of Informatics Aristotle University of Thessaloniki 54124 Thessaloniki, Greece e-mail: 1 vchou@csd.auth.gr , 2 amiliou@csd.auth.gr Miltiadis N. Hatalis Department of Electrical & Computer Engineering Lehigh University Bethlehem, PA 18015, USA e-mail: mkh1@lehigh.edu Abstract— In this paper we present the optimization of a Capacitive Micromachined Ultrasonic Transducer (CMUT) array that performs as a tactile display using an electrical equivalent circuit model and the SPICE program. The array implements a “pixel” of the display and is used to focus airborne ultrasound energy on the skin surface. The design of the array is optimized for high output so that the pressure field generated by the focused ultrasound waves excites the mechanoreceptors under the skin and transmits tactile information. The geometry of the individual transducer and the array are optimized so that the medium presents maximum impedance and the membrane oscillates with maximum deflection. Finite element analysis of the CMUT and the CMUT phased array is used to verify the SPICE results. In order to verify the feasibility of the design, the pressure at focal point is compared with the pressure threshold required for mechanoreceptor excitation. Keywords-component; Tactile display, CMUT, MEMS, Ultrasonics I. INTRODUCTION Tactile displays are human computer interfaces that utilize the sense of tactation and convey information from the machine to humans. Tactile displays can reproduce as truly as possible the tactile parameters of an object, such as shape, surface texture, roughness, and temperature using an alternate channel, the sense of touch. Tactile information is displayed using tactile transducers, or tactors [1]. The importance of the tactile feedback in designing user interfaces has been recognized in a variety of fields and for this reason there is a growing family of applications for tactile displays including Text and Graphics, Medical, Entertainment and Education, Military, Engineering applications-assisting the blind and visually impaired, Virtual environment and Tactile displays embedded in consumer electronics and wearable devices. Tactile devices allow the user to read the computer screen and obtain text-based information using refreshable Braille displays, Braille readers and/or tactile mice in direct- manipulation systems. These applications in conjunction with screen readers and other software, made it possible for Braille readers to enjoy much of the flexibility navigation of electronic texts. Teletaction allows sensing and display of tactile information to the surgeon. In teletaction, a tactile sensor array can be used to sense contact properties remotely, increasing safety and reliability in present minimal invasive procedures and bring the advantages of these techniques to other, more complex procedures, which are not possible today. Adding a tactile interface to computer animation will permit end-users to interact physically with game environments, i.e. feel the recoil from a weapon, encounter turbulence in the flight simulation or walk into a physical wall. Tactile stimulators can be used to simulate sensations from electrical shock and bee stings to bullet impacts, as part of a 3-D movie or gaming experience. Tactile displays have shown to provide improved situation awareness to operators of high performance weapon platforms, and to improve their ability to spatially track targets and sources of information. Tactile displays can reduce perceived workload by its easy-to-interpret, intuitive nature, and can convey information without diverting the user's attention away from the operational task at hand. There are currently four main applications for which tactile displays are considered to have great potential for military applications: orientation, navigation, communication and training and simulation. Tactile interfaces can also be used as a channel for communication with miniature handheld computing devices such as mobile phones, PDAs, and pagers or wearable devices providing more effective, comfortable and enjoyable interaction. Some of the uses will include navigation, notification though touch, monitor the status of a process or use of gestures to interact with the device. Tactile perception can be induced by directly stimulating the human skin, which is sensitive to pressure (positive or negative), vibration, temperature, electric voltage and current. The Tactile displays are utilizing one of the skin modalities: (i) vibration, (ii) pressure and stroking, (iii) skin stretch and (iv) texture, stroking, and fluttering. Skin modalities are the channels through which energy is transmitted to the skin and excites the mechanoreceptors that are responsible for the sense of tactation. The devices implemented so far, exploit the modalities of the skin's sensors and can be classified into the following major categories, based on the modality used: - pressure (mechanical energy), 2012 16th Panhellenic Conference on Informatics 978-0-7695-4825-8/12 $26.00 © 2012 IEEE DOI 10.1109/PCi.2012.61 228