Dirk Brokken

A numerical‐experimental method to characterize the non‐linear mechanical behaviour of human skin

Background/aims: Human skin is a complex tissue consisting of several distinct layers. Each layer consists of various components with a specific structure. To gain a better insight into the overall mechanical behaviour of the skin, we wish to study the mechanical properties of the different layers. A numerical‐experimental method was developed to characterize the non‐linear mechanical behaviour of human dermis.

Influence of hydration and experimental length scale on the mechanical response of human skin in vivo, using optical coherence tomography

Backgrounds/aims: Human skin is a complex tissue consisting of different layers. To gain better insight into the mechanical behaviour of different skin layers, the mechanical response was studied with experiments of various length scales. Also, the influence of (superficial) hydration on the mechanical response is studied. The work is based on the hypothesis that experiments with different length scales represent the mechanical behaviour of different skin layers. For suction, this means that a large aperture diameter reflects the behaviour of mainly dermis, whereas a very small diameter reflects the behaviour of only the top layer of the skin.

A body-conforming tactile jacket to enrich movie viewing

Adding haptic stimulation to movies is a promising step in creating more emotionally immersive experiences. To explore the potential of this concept, we have created a wearable tactile jacket that is used to deliver movie-specific tactile stimuli to the viewers body that are specifically targeted to influence the viewers emotions. Immersion was evaluated in a user test using questionnaires and physiological measurements. The findings show promising effects of the haptic stimuli that need to be substantiated in further more refined user tests.

Combined driving and sensing circuitry for dielectric elastomer actuators in mobile applications

Dielectric elastomer stack actuators (DESA) promise breakthrough functionality in user interfaces by enabling freely programmable surfaces with various shapes. Besides the fundamental advantages of this technology, like comparatively low energy consumption, it is well known that these actuators can be used as sensors simultaneously. The work we present in this paper is focused on the implementation of a DEA-based tactile display into a mobile device. The generation of the driving voltage of up to 1.1 kV out of a common rechargeable battery and the implementation of the sensor functionality are the most challenging tasks. To realize a large range of tactile experiences, both static and dynamic driving voltages are required. We present a structure combining different step-up topologies to realize the driving unit. The final circuitry complies with typical requirements for mobile devices, like small size, low weight, high efficiency and low costs. The sensing functionality has to be realized for different actuator elements regardless of their actual state. An additional sensing layer on top or within the actuators would cause a higher fabrication effort and additional interconnections. Therefore, we developed a high voltage compatible sensing system. The circuitry allows sensing of user input at every actuator element. Both circuits are implemented into a handheld-like device.

Dynamic Game Balancing by Recognizing Affect

Dynamic game balancing concerns changing parameters in a game to avoid undesired player emotions, such as boredom and frustration. This is e.g. done by adjusting the games difficulty level to the (increasing) skill level of the player during the game. Currently, most balancing techniques are based on in-game performance, such as the players position in a race. This is, however, insufficient since different types of players exist, with different goals, preferences and emotional responses. Therefore, to deal effectively with a players emotions, a game needs to look beyond the players performance. This paper provides an overview of two groups of potentially useful sources for dynamic game balancing: Overt behavior and physiological responses. In addition, we present EMO-Pacman, a design case that aims to implement these new balancing techniques into the game Pac-Man.

Creating an Emotionally Adaptive Game

To optimize a players experience, an emotionally adaptive game continuously adapts its mechanics to the players emotional state, measured in terms of emotion-data. This paper presents the first of two studies that aim to realize an emotionally adaptive game. It investigates the relations between game mechanics, a players emotional state and his/her emotion-data. In an experiment, one game mechanic (speed) was manipulated. Emotional state was self-reported in terms of valence, arousal and boredom-frustration-enjoyment. In addition, a number of (mainly physiology-based) emotion-data features were measured. Correlations were found between the valence/arousal reports and the emotion-data features. In addition, seven emotion-data features were found to distinguish between a boring, frustrating and enjoying game mode. Taken together, these features convey sufficient data to create a first version of an emotionally adaptive game.

Correlations between small aperture skin suction parameters: statistical analysis and mechanical model

Background/aims: Skin suction experiments are widely used in order to evaluate the effects of skin treatments, both for cosmetic and for dermatological purposes. Classically, the elevation of the skin is measured at different discrete time instances after the pressure has been changed. Relations between the classical parameters – Uv, Ur, Ue and Uf – have been investigated and used in order to develop a new model for interpreting the mechanical properties of the skin.

Same or different? Recollection of or empathizing with an emotional event from the perspective of appraisal models

The same stimulus can evoke different emotions for different individuals. Incorporating personalized construal of stimuli is how appraisal models differ from dimensional models of emotion. Scherer formulated a model of the cognitive antecedents of emotions and analyzed recollections of events and emotions that his participants provided. In the present study, we were interested whether Scherers appraisal model also applies to a situation in which participants have to empathize with a photo by building a story around the event depicted. Our results show that recollecting a personal emotional event and empathizing with a photo seem to be similar processes. Results of machine-learning techniques, however, show lacking performance of classifications to express discrete emotion labels in terms of appraisal data.