In addition to display technology, it is important to focus on interactions through direct input devices that involve a sense of touch (Forlines et al., 2006). As new models of mobile tablets, smartphones with large screens, and compatible styli have been released, users are given more opportunities for elaborate manipulation; for example, note-taking, sketching, and painting using styli are more convenient. Given this trend, it is important to understand three aspects of typical touch interactions involved in creative activities such as drawing and handwriting: (1) “hand and tool,” (2) “tool and surface,” and (3) “hand and surface” interactions (Sulaiman and Blandford, 2004). Drawing or writing on the surface of mobile devices with styli is similar to doing so with pen on paper in the real world. This implies that adding haptic cues such as softness, hardness, or stiffness to both the input device and the output display can mimic the surface texture properties of traditional drawing tools, enhancing tactile experience. In spite of the importance of providing a rich tactual experience, most newly released styli have been improved in terms of functional benefits (such as palm rejection and increased precision) and redesigned aesthetic features (in order to make them a natural fit for note-taking) without taking into account subjective satisfaction. It is therefore necessary to consider differences in the material properties of both touch-based screens and input devices.
In light of the importance of this somewhat neglected area, the present study was carried out to examine the effects of an elastic touchscreen and input devices with different degrees of softness on user task performance and subjective evaluation. In particular, the degree of hardness/softness of the surface of the touchscreen and pen-based input devices was manipulated in order to present alternative approaches for the design of touch surfaces without using any form of mechanical actuation. The finger was used to provide a performance baseline. Considering the difference of the hardness/softness of the touchscreen and devices, both behavioral and self-report data were gathered in a lab experiment measuring task performance while playing a tapping-based game, along with subjective satisfaction of pressing down on the surface, pleasantness, helpfulness, finger fatigue, and degree of elasticity. The importance of tactile sensation cannot be overemphasized; touch perception, which can affect user emotions, enables the user to detect a product’s usefulness and usability (Keinonen, 1998). In this respect, the findings of the current study help designers and developers to understand the human factors underlying direct touch-based interaction, informing the design of haptic products that provide a pleasant tactile experience.