Designing for interactive wearable heat feedback
Mario Boot
Exertion Games Lab and University van Amsterdam mario.boot.boot@student.uva.nl
ABSTRACT
This paper presents rationales for designing body-centered expe-riences with interactive wearable heat feedback. The backdrop of this work is a shift from rationalism-based computer science to phenomenology-based embodied interaction. We articulate what we learn from our research through design approach. Via this method, an interactive wearable is designed in 2 iterations. Figure 1 shows the heating pad element of the wearable. The design process evolved from low-fidelity sketching to an aesthetic yet functional implementation. Through dialogue and reflection it can be inferred that wearable thermal stimuli can be a pleasant but rather slow interaction modality, which can make persons more aware of their environment and themselves. Wearable thermal stimuli should in-corporate both heat and cold, and hybrid materials can be leveraged to design the materiality of thermal stimuli devices. These ratio-nales are targeted to designers and design researchers situated in the interdisciplinary ensemble of fashion design, human-computer interaction, and electrical engineering. We hope these proceedings contribute to the enrichment of body-centered interaction.
KEYWORDS
thermal stimuli, body-centered interaction, e-textiles, wearables
1
INTRODUCTION
1.1
Context
An evolution is observable within HCI [14, 19]. Research and prac-tice came from man-machine functionality and moved on towards an orientation to usability. Currently, the paradigm seems to be shifting again: towards an emphasis on experiences around embod-ied interaction. This study is situated in this most recent evolution: the 3rd wave of HCI. Within this paradigm shift, we observe a growing need for non-traditional interfaces [24].
1.2
Purpose
This study aims on investigating a particular non-traditional inter-face: heat. The goal for this investigation is to address the research question: what to consider when designing body-centered experi-ences with wearable heat feedback?
We aim on extending the design space and knowledge about thermal stimuli. We aim on extending existing studies in three ways: 1) we contribute insights on heat feedback that have a higher degree of interactivity and wearability than previously investigated, 2) with a field study we explore the validity of design decisions made in the design for wearable heat feedback, and 3) we continue the investigation on the materiality of heat. We specifically intend to approach this opportunity from an interdisciplinary perspective which blends fashion design and electrical engineering into HCI.
Figure 1: The design process resulted in a heating pad which is depicted in this picture.
1.3
Motivation
Three motivations drive this study. Firstly, we agree to statements that we need interactive solutions that align with the desires, abil-ities and needs of our human bodies [13]. The second reason is concerned with the unique yet seemingly under-explored features of leveraging wearable heat feedback in HCI. Therefore, we believe existing work on temperature feedback deserves more attention. Lastly, recent advancements in e-textiles seem to offer exciting potential for establishing such experiences [25, 30, 46].
1.4
Research Approach
The research approach entails multiple methods, which allows for triangulation of data. We believe our Research through Design (RtD [50]) approach is well suited for our exploration, because it supports rigor and relevance during design and analysis while allowing an interdisciplinary exploration. Relevant experts support the design process in a participatory design fashion [7]. A field study validates the design decisions. Observations and informal interviews provide insight in the first-hand experience of our designs. Data is gathered by taking notes, photos, and videos. Categorizing reoccurring topics into more general themes in a inductive analysis [9] approach establishes our final recommendations and conclusions.
1.5
Outcome
This study can be considered as an exploration more than a confir-mation. This exploration can serve as an inspirational springboard for future investigations on heat feedback. It will be described how heat feedback might provide cues in settings where meaningful communication is desired, and how heat might unobtrusively warm up people in ambient intelligence settings. It will be explained how hardware requirements constrains practicalities of wearing wear-able stimuli systems, and how day to day activities might complicate focusing on the sensation of heat.
These rationales are grounded in analysis of 1) the experiences of the artifact to which our design process led and 2) the design process of this artifact. The artifact that emerged from the design process is depicted in Figure 1.
These outcomes are devised for professionals and academics who work as designers and design researchers, in particular those with an interdisciplinary mindset in the fields of human-computer interaction, fashion design and electrical engineering.
1.6
Structure and terminology
Overall, as we are interested in experiential aspects, we decide to focus mainly on subjective interpretations of our design. That is, the ”Leib” perspective, as will be explained in the Related Work section. Technicalities and elaborate descriptions of objective measurements can be considered a ”Korper” perspective, therefore it is decided to only cover these very briefly.
The terms ”heat”, ”heat feedback”, ”thermal stimuli” and ”tem-perature feedback” will be used interchangeably. This terminology refers to the process of the heating pad providing heat to the body. In the discussion a specification of thermal stimuli will be given. All temperatures mentioned are in degrees Celsius.
This research has been conducted under ethics approval number HREC/CHEAN 20912. All study participants are anonymized and will be referred to as Px, where x identifies a person by a number. In line with [34, 39], people and study participants will be referred to as such and not as ”users”.
2
RELATED WORK
2.1
Wider context: a paradigm shift
The backdrop of our study is formed by a paradigm shift within HCI. Thought patterns within the HCI community can be categorized into three waves [14, 19]. The first wave is rooted in the engineering of functionality, and in the second wave cognitive science was embraced. Currently the paradigm appears to have shifted to a third wave which is based on phenomenological and pragmatist philosophies. This investigation is situated in the third wave.
McCarty and Wright [28] elaborate on their interpretation of this third wave: ”a broadening of focus from computers to a wide range of interactive technologies and from work-related tasks to lived ex-perience.” (p. 3). They outline that the current trend focuses less on instrumental application of technology. Rather, emphasis is being put on the meaning and implications of experiencing technology instead. Dourish contributed to this third wave with a seminal work on embodied interaction [13], and others have confirmed there is more to human-computer interaction than the currently common screen-, mouse- and keyboard-based interactions [15, 21, 24]. These macro trends inspire our general direction, and we continue with focusing on experiencing technology via our body.
2.2
Body-centered interaction
It is relevant to understand the challenges and opportunities our body brings along. Shusterman’s proposal on ”somaesthethics” [40] provides fundamental insights in this regard. Hook et al. de-scribe what they learned from Shusterman’s proposal: ”By putting together the two words soma, the body, with aesthetics, our sen-sory appreciations, he [Shusterman] draws our attention to the
importance of our bodily movements as part of our ways of being and thinking.” (p. 3132). The authors emphasize the importance of considering ”the pleasures and displeasures, beats, rhythms, and richness of the living body” [21].
How does this link to computing? In [31] it is written that ”the aim of body-centric computing is to design products and services that reposition the role of the body from the periphery to the center of the interaction, thus becoming body-friendly”. Furthermore, the article states that ”body-driven and technology-driven development must be balanced”.
Mueller et. al [32] provide inspiration on what they call ”ex-periencing the body as play”. They state that if designers retain a limited view on experiencing technology, ”players will not be able to benefit fully from the many benefits associated with bodily games and play”. We agree and align with their proposal that dis-tinguishes two perspectives: the Korper, and the Leib. Mueller et. al. explain the Korper as the objectified, physical body and the Leib as the living human being. The strategies in their proposal support intertwining the Korper and the Leib closer together. Because their work is based on phenomenological philosophies like Hook’s study, we believe that these two perspectives are also relevant for us.
2.3
Experiencing heat through our body
Designing for heat implies relating to thermodynamics. It has been shown that sensing and regulating body temperature is indispens-able for human survival [27]. Furthermore, thermoregulation has been studied in marathon runners [26], astronauts [45] and health-care patients [12]. However, we consider these as rather ”Korper-oriented” cases, and these studies do not focus on human-computer interaction.
With regards to thermoregulation and HCI, thermal stimuli is called a non-traditional interface [24], categorized under the umbrella of haptics [15, 43]. We learn from a number of studies [35, 38, 42, 49], in short, that heat is generally qualified as contain-ing unique features that are hard to identify or virtually absent in other sensory experiences. Interacting with heat is feasible and is characterized as subtle, gentle, and comfortable. However, heat is also relatively slow, sluggish, and does not have a high granularity in the communication of information. Studies on thermal stimuli about guiding awareness [8, 23] teaches us that heat is suitable for meditation settings.
However, it can be observed that wearability, interactivity and context-awareness of thermal stimuli is not substantially investi-gated. A preliminary systematic literature search was conducted via Google Scholar and the Digital Library of the Association of Computing Machinery. Relevant literature was searched using the keywords ”temperature feedback”, ”thermal stimuli”, ”wearable heat display”, ”portable interactive heat system” in various combi-nations. No well-established literature was found. This observation is a key motivator for this investigation.
2.4
E-textiles
Lastly, as we intend to create knowledge about thermal stimuli in a wearable artefact that will be worn on the body, we briefly highlight advancements in ”e-textiles”. Exciting new opportunities appear to arise [30, 46]. Fabrics that can generate electricity by
Figure 2: Left - A heating vest; Right - a fashionable integra-tion of clothing and computing.
harvesting human body movement energy [25] are, in the longer term, of direct relevance to this study.
Clothing that integrates heating elements is widely and commer-cially available. Figure 2a illustrates such a vest [16]. It contains already a degree of interaction, because it can be controlled by a smartphone application via a wireless connection. The designs of Marina Toeters [47], who designs and prototypes innovative textile products and garments, provided further inspiration. One of her produces is illustrated in Figure 2b.
In summary, within HCI a trend is occurring which moves away from instrumental use of technology towards a ”Korper and Leib” integration that honours the subtle richness of experiencing our living body via technology. Interacting with heat has been studied before, but not extensively with a wearable system for enriching bodily interaction. We proceed with clarifying the approach we chose for achieving our aims in this context.
3
RESEARCH APPROACH
3.1
Research questions
Overall, we are interested in the rationales that designers and design researchers should take into account when designing body-entered experiences for heat as a modality in wearable interactive systems. The 2 subquestions below support answering the following main research question: What to consider when designing body-centered experiences with wearable heat feedback?
3.1.1 What are the experiential characteristics of thermal stimuli? This question serves to reveal an explanation how experiencing thermal stimuli can be qualified from a ”Leib”-perspective.
3.1.2 What are the opportunities and challenges in designing the wearability of thermal stimuli? This subquestion concerns the porta-bility of systems for thermal stimuli. In line with advancements in e-textiles and the advent of wearable devices, it appears to be useful to understand how thermal stimuli systems can be designed so that they can be worn on the body.
3.2
Research Approach
3.2.1 Combining multiple methods. This study attempts to ad-dress the main research question in a triangulation approach. The following approaches are combined:
Figure 3: Left - the first wearable prototype; Right - a con-ceptual drawing of the waist belt on the body
• RtD [44, 50] for designing and implementing a functional artifact;
• An ”in-the-wild” field study [10, 11] for validating our design decisions.
It must be acknowledged that the RtD efforts proceeded virtually simultaneously with the Field Study. An iterative design approach, rapid prototyping and so-called ”applicability checks” [37], this supports making quick adjustments to refine prototypes. A short explanation for our choice of a RtD approach is given in this section, and activities within the RtD approach will be described extensively in Section 4. Section 5 clarifies details of the Field Study.
3.2.2 Research through Design. A RtD approach appears to fit the central theme of this study for two reasons. In this way we can both: 1) design an experience around an application of thermal stim-uli, and 2) create abstract knowledge about the experience of such application and the design thereof. Designing and implementing an actual wearable enriches understanding of the design process. This artifact supports provoking experiences in our study participants, which are analyzed to create knowledge on an abstract level.
3.2.3 Data Gathering. The design process is documented in the form of photographs, videos, and note-taking. Observations and reflective dialogues with both the design collaborators and the study participants provided opportunities for data gathering [6].
3.2.4 Data Analysis. A qualitative inductive analysis [9] ap-proach is used to organize emerging topics into central themes. Topics emerged during design and field study activities. Reoccur-ring topics are identified, and based on inductive reasoning these reoccurring topics are categorized into overarching themes. These themes form the main input for the recommendations and conclu-sions in the last chapters of this study.
4
ITERATIVE DESIGN
4.1
Iteration 1
The purpose of the first design iteration is to obtain a preliminary understanding of designing for an experience with thermal stimuli. We are inspired by the Minimum Viable Product concept [20, 33] and by online tutorials [1–3] with regards to the physicality and technicality of the artifact. The design steps are explained now.
4.1.1 Conceptualizing and rapid-prototyping a hardware setup. Thermal stimuli was integrated into a wearable for 4 reasons:
• Merging temperature feedback into a wearable allows us to explore the design space for wearable thermal stimuli; • A wearable aligns with recent advancements in the fields
of e-textiles and HCI;
• A wearable increases movement range of the wearer, be-cause no wiring to e.g. a electricity socket on a fixed posi-tion in a room is needed;
• As heat is inherently conveyed through some material, de-signing a wearable supports understanding the materiality of heat.
A preliminary understanding of the function, form and posi-tioning of the wearable was obtained via paper-based sketching. Findings of [18] supported understanding the positioning of the system components. A choice was made for a waist belt to reduce intrusion of the hardware components into the personal body space of the wearer. A Velcro strap supports compatibility with a range of body sizes.
We rapid-prototyped a low-key hardware setup. Existing work [8, 23] indicated that a commercially available low-cost heating pad can be used. A combination of hardware devices and a software script on an Arduino-based microcontroller regulates powering the heating pad. The microcontroller is controlled from a smartphone via Bluetooth.
4.1.2 Experimenting with thermal stimuli. This low-fidelity pro-totype enables the wearer to experience heat. To understand the effects of Thand∆Th(= respectively the temperature of the heating
pad and the rate of change of the temperature of the heating pad) on the experience of heat, we experimented with varying Voltage be-tween 6-11 Volts. Varying∆Thvia wireless control created heating
patterns.
An interview with a thermodynamics expert revealed that Th
depends on three main aspects. These aspects are insulation, skin temperature, and the heating pad’s ambient environment tempera-ture. These laws of thermodynamics have implications for both the experience of heat and the design of the wearable, which is covered later in this paper.
4.2
Iteration 2
The second iteration is focused on two aspects in particular: 1) the interactivity of the heating pad and its responsiveness to its environment, and 2) the influence of the artifact’s physical form and appearance on the experience of the heat and wearable.
4.2.1 Designing for automated interaction with heat. To increase the degree of automation in the interaction between the heating pad, the environment and the person, we add a temperature sensor to our system which measures the ambient environment temperature. A script was developed for automatically heating up and cooling down the heating pad according to the environment temperature. Figure 5 depicts the flow of interaction between the agents in this experience. The system is designed so that it is looping a script that performs a function which is executed upon a trigger. The thermometer acts as sensor as main input for the system. The heating pad that produces heat acts as actuator. Thermometer
Figure 4: Rapid prototyping resulted in a number of artifacts for the heating pad. Clockwise: the conductive thread; the artifact that emerged to be the favorite; examples of proto-typed heating pads.
Figure 5: A flowchart that summarizes the interaction be-tween the study participant and the system.
measurements are transformed via the system to heat produced by the heating element.
The function that is performed upon a trigger comprises that the heating pad is powered for +- 30 seconds, after which it switches off. This heat-up to a mildly warm temperature of about 45-50 degrees and subsequent cool-down is called a heating pattern. Moving in between temperature zones triggers the script to execute the function. The trigger is calibrated so that the function is executed if the wearer of the system moves in between temperature zones. Temperature zones that the system is able to detect are an indoor office space and an outdoor temperature. The function is executed whenever a significant change of temperature is detected, regardless from whether this is a positive or negative change. We acknowledge that this description lacks precision in terms of exact temperatures, significance, error rates, and timings. Also, more intricate heating patterns might be appropriate. We decide to leave this to future research.
Iteration Participant Duration Setting Activities Undertaken Assistance 1 P1 1h Outdoor Office work Yes
P2 2h Research Lab Walking outdoors Yes P3 2h Research Lab Office work Yes P4 1h Research Lab Office work Yes P5 1h Research Lab Office work Yes 2 P1 3h Outdoor and indoor Commuting Partially
P6 1h Outdoor Walking outdoors Yes P6 2.5h Car Car driving and commuting No P7 3h Research Lab Office work No P8 0.5h Outdoor Walking outdoor Yes P9 1h Outdoor and indoor Talking lunch walk Partially P2 2h Outdoor and indoor Commuting No P11 2h Outdoor and indoor Commuting and shopping No P12 1h Outdoor and indoor Commuting and shopping No P13 1h Outdoor and indoor Dinner and walking to restaurant No P14 2h Outdoor and indoor Commuting No
Table 1: Overview of details of study participants.
4.2.2 Designing the materiality of heat. Testing during itera-tion 1 revealed that the design of the waist belt appeared to study participants as rather utilitarian and suspicious. Engagement was sought with a senior fashion designer and an industrial designer in a participatory design fashion [7], in order to turn the challenge of designing the materiality into an opportunity for artistic expression. The purpose of this engagement is to improve the fashionability and wearability. In line with [23] which encourages designers to consider the materiality of heat, we considered the materiality of the object through which heat is conveyed in particular.
The yellow plastic heating pad was considered by both study participants and the research team as rather intrusive. The plastic makes a crackling sound which does not intuitively match with the silence of heat, and the plastic is not breathable which limits transpiration of the skin.
A short rapid-prototyping session (see the lower image in Figure 4) was conducted to align the look and feel of the artifact better to our body. We intended in particular to minimize perceptions of suspicion and safety that a utilitarian designs might evoke.
Conductive thread (an example is depicted in Figure 4, upper left) can be considered as an opportunity in the design of wearable heat feedback. A Brother Innovis 950 embroidery machine was used to sow a conductive thread made of 316L stainless steel with a resistance of 10 ohm per foot. This conductive thread comprises the heating element.
This resulted in a soft-feeling, pleasant-looking and quiet-sounding heating pad with breathable fabrics (Figure 4, upper right), and we believe this artifact facilitates positive emotional engagement.
During our prototyping, we discovered the importance of taking the following design considerations into account:
• The pattern that is sewn with the conductive thread. Sewing a heart-shaped pattern (Figure 4, most left item on picture) with conductive thread as heating element was a pivotal step in our design process as it evoked more positive emo-tions than the utilitarian waist belt in iteration 1;
• Selection of the fabric. The fabric should be flexible, breath-able, durable and soft;
• The size of the heating element in the heating pad sowed with conductive thread. The size of the heating pad should be at least 5x5 to accommodate for our body’s relative inaccuracy in detecting temperature differences [22]; • The distance between the conductive threads. This supports
reducing the likelihood of short circuiting the electrical system;
• The length of the conductive thread. This was minimized in order to reduce required battery capacity.
4.2.3 Designing the wearability of heat. The positioning of the heating pad caused a great deal of discussion, both within our research group and during the testing. We chose to separate the heating pad from the waist belt to enable flexibility in positioning the heating pad. This allows the study participants to place the heating pad on the body where they felt most comfortable wearing the heating pad.
5
STUDYING DESIGN DECISIONS
IN-THE-WILD
Design decisions made during the process of designing our expe-rience around a wearable system for thermal stimuli have been validated on an ongoing basis. This ”in the wild”-study was con-ducted in order to gather data that supports answering the research questions. In addition, testing outside the controlled confines of a research lab exposes our design decisions to everyday situations, which supports revealing unexpected construction errors.
5.1
Study environment
Design decisions have been tested in three settings: 1) within the confined space of the research lab; 2) on the university campus, assisted by a member of the research team and 3) outside, without assistance from the research team. Testing in this variety of settings
supports understanding the uncontrolled nature of environments in which such wearable might be used.
5.2
Study participant recruitment
Study participants were sampled in the style of convenience sam-pling [9]. This convenience sample accommodates the time- and resource constraints of the resource team, while still offering po-tential for revealing valuable insights. Professional colleagues and personal acquaintances of the research team and from within the community of the research lab were asked to participate.
5.3
Study setup
14 persons participated in the field study. All participants signed a consent form to confirm their voluntary participation and under-standing of instructions and safety measures.
All participants were instructed to:
• Wear the waist belt and heating pad for at least 45 minutes while they continued undertaking their regular day-to-day activities;
• Be aware of how they experience the heat and the waist belt;
• Pay specific attention to the sensation of warmth • Attempt to understand the pattern in which the heating
pad warms up and cools down, especially in relation to moving between temperature zones;
• Be aware that safety measures were implemented into the system to reduce overheating, burning and melting risks; • Verbalize their feelings about their experience;
• Raise any concerns, questions and remarks immediately. Anonymized details of study participants are presented in Table 1. The column assistance concerns to what extent a member of the research team assisted the study participant during the field study. The degree of assistance depended on two aspects: 1) the willingness of the participant to undertake the test alone (some participants felt more comfortable when assisted due to potential unexpected events) and 2) the stage of development of the prototype, because early implementations needed continuous adjustment and repositioning of components. Varying the degree of assistance allows for both observing study participant’s reactions for those who were assisted, as reduce influence and bias from the research assistant for the non-assisted participants.
5.4
Data Gathering
Data gathering during the field study took place in the following ways. As the study participants were instructed to articulate their thoughts, an informal think-aloud protocol allowed to observe their verbalizations of their experience. In addition, informal conversa-tions with the study participants during and after the field studies were held. A set of questions and topics to be addressed in these conversations was devised. During these conversations, questions were focused on the subjective nature of the experience [36] our wearable. Note-taking during all data gathering activities was the main method for registering the data.
6
RESULTS FROM THE FIELD STUDY
The results gathered during the field study can be categorized into 6 categories. We now present these categories.
6.1
How does heat feel?
Around 25-35 degrees, some study participants were not exactly sure whether they did actually feel heat in the heating pad, as P2 said: ”Do I feel the heating pad, or did my skin just heat the heating pad, and do I feel my own heat now?”.
The opposite end of the spectrum lies above temperatures around 55 degrees, which some study participants perceive as becoming uncomfortable: ”I need to take it off now, this becomes too hot” (P5).
The middle range lies between 35 and 55 degrees. In this range, study participants appreciate a sensation of comfort that is evoked by mildly warm temperatures: ”This warmth feels soothing, and I like that”, as P4 articulated.
On temperatures above 50 degrees participants feel that the warmth is attracting their attention, which makes it difficult to focus on other tasks: ”It’s hard to focus on something else now” (P4). Heat can work as a distraction, as P7 said: ”My attention was distracted immediately from my activity of reading”. Overall, study participants enjoyed the warmth, which is best captured in P5’s statement: ”the warmth feels soothing and I really like that”.
6.2
When is heat felt?
Based on comments from study participants, one could say that it appears to be not always straightforward to determine whether heat is being felt or not.
P13 had a particularly interesting comment to which we return in the discussion. The content of the conversation was about the moment that heat was being felt. P13 said: ”it is definitely some-thing you are aware of subconsciously of before you are consciously aware of it”.
While conversing about the field test with P10, this person said: ”I do not really know whether I was feeling the heat or not, be-cause I was focused on walking and talking with you [the research assistant]”.
Nevertheless, some participants were able to determine the start of their feeling with higher precision. P1 said: ”Yes, I feel the heat coming”. P6 said: “The heat increased rapidly and I enjoyed the warmth entering my wrist” and ”It’s really interesting that this heating pattern feels pulsating, it is like it is alive. I like it when the heat comes and goes – if the heat is constantly there it becomes boring”.
In addition, cooling down the heating pad appears to be different from heating up. P9 said: ”Heating up was rather fast, but when I felt the temperature going down it seemed like some residual heat remained in the heating pad”.
6.3
Wearability of designed artifact
A custom-made heating pad was integrated into a piece of garment. The hardware is integrated into a commercially available belt with a pocket that can be worn on the waist. The hardware system is self-contained so that no wiring is need to e.g. an electricity socket
on a fixed position on a wall. This aspects make the system fully wearable.
During iteration 1, P2 exclaimed a remark that summarizes in our opinion the essence of designing for wearability. P2 said: “only if the hardware would be more forgiving”.
Although there might be potential to design provocative arti-facts, in our research we decided to develop artifacts that evoked positive engagement and associations. To avoid associations like fear and/or anxiety and in line with commercial availability of con-ductive threads, we chose to sow a heating pad with concon-ductive thread ourselves.
The soft-feeling heating pad that resulted in iteration 2 was generally received well by the study participants. P6 said about a heart-shaped test prototype: “it makes me want to snuggle up to it”, and P12 said about the heating pad from iteration 2 that ”it feels nice and soft on my skin”.
About the position the heating pad on the body - study partici-pants experienced the system with various positions of the heating pad. The heat pad has been positioned on the back at the top of the spine and at the lower end of the spine, on the wrist, on the shoulder, and on the stomach. We experimented with placing the heating pad both directly at the skin and on the body with a layer of clothing in between the heating pad and the skin.
P6 articulated “I think my wrist is more sensitive”, and P4 said: “placement on the top of the spine at my back provided a pleasant warmness when going outside where it is cold”. P11 said about the heart-shaped prototype that ”it makes me think that it fits on my chest”. P9 said: ”a smaller pad on the back might be rather comfortable when going to outside where it’s cold”.
6.4
Thermal feedback that understands
Some participants made comments about adjusting Th to their
preferences. P4 said: ”I feel the heat was too hot and I wanted it to become less hot. P9 literally said: ”I want the system to understand me”. P9 said this in line with earlier comments that she liked the warmth, but that the warmth sometimes became too hot. P9 gave a recommendation that ”some sort of benchmark can support anticipating personal preferences, because I acknowledge that for me it might be too hot but others might like it”.
6.5
Safety and suspicion
Safety turned out to be a concern for some study participants. P3 said: “Will it set on fire”, and P2 said: “I’m happy I was not electrocuted”. P4 verbalized: “it looks kind of scary, with all the wires”, and P5 said “it looks like a bomb”. We addressed safety concerns by establishing safety by hardware design, by including a fuse in the technical system. After implementing this feature and including this implementation in the instruction of the field study, no more comments were made about electrical safety concerns.
Concerns about potential suspicion from pedestrians and other commuters on the street were raised. Both P6 and P9 felt slightly uncomfortable when they were asked to walk outside with a ther-mometer and wiring sticking out of their clothing. P6 said: ”I feel more comfortable if a research assistant accompanies me”, and P9 said: ”What if someone sees the thermometer and thinks I have malicious intent?”.
6.6
Agency
Finally we highlight that P3, P11 and P12 all took some sort of control over the system. P3 was wearing the waist belt while driving in the car. She opened the windows so the temperature inside the car would decrease, because she was curious to understand if and how that would affect Th. P11 said: ”When waiting for the traffic
light, I held my fingers around the thermometer in the hope the heating pad would warm up, because I was cold. Right after the start of the test, P12 articulated that he would play around with trying to vary the thermometer’s temperature, to see how that would affect the Th.
7
DISCUSSION
By reflecting on the findings from the related work, design pro-cess and results of the field study, a number of themes emerge via inductive analysis. Each theme has a number of implications and complications for the wider community of designers and design researchers. These themes are now discussed.
7.1
Features of heat as opportunities to signify
Firstly, two rather odd features in HCI are evaluated: slowness, and low granularity. Both features relate to the first subquestion and characterize the experience of heat.
Heat as an interaction modality is relatively slow, and it does not seem to contain a high granularity of information. We recommend designers and designer and design researchers to pay attention to the one-dimensionality and inertia of heat. In [22] it is stated that ”it seems unlikely that information that needs to be responded to rapidly should be presented using this sensory modality” (p.58). However, that study does not describe the potential benefits of this slowness.
A comparison with a visual notification on a screen can be made. Within milliseconds after the visual notification appears, the viewer starts thinking about it. In addition, this notification can present a complex set of information contained in visual and textual compo-nents. In contrast, heat patterns (provided that dangerously high temperatures are avoided) take at least seconds before being no-ticed. Heat is silent, and heat might serve as a gentle background reminder.
We argue that these features of heat might play a very welcome role, as has been demonstrated by other research on meditative-focused scenarios [8, 23]. As Marc Weiser wrote in 1996: “Thus may design of calm technology come to play a central role in a more humanly empowered twenty-first century” [48].
Nevertheless, it needs to be decided what a slow heating pattern is supposed to mean. In line with P5’s comments, we believe that soothingness of warmth is particularly well positioned to serve us meaning in a gentle way. The field of semiotics might be of benefit in designing such meaning [5]. After all, what is heat supposed to signify?
7.2
Accommodating desires to stay
comfortably warm
In line with P13’s comment regarding that his body felt heat be-fore the heat reached his thoughts, it appears to be relevant to
understand how heat interacts with subconsciousness and cogni-tive thinking. Sensing of heat has been studied before, e.g. [22] which writes: ”The skin is extremely sensitive […] the base of the thumb human subjects can resolve a difference of 0.02 - 0.07 de-grees”. However, we consider this as a rather ”Korper”-oriented perspective, and it does not tell much about how thermal stimuli moves from subconscious bodily processes to active thoughts about the thermal stimuli.
Understanding the interaction of heat with the person who is subject to the heat can be illustrated by the following example. Imagine the moment that we become aware of our shivering cold feet and hands. ”Oh”, one thinks, ”I am really cold now and I guess I should have taken on extra clothes two hours ago already”. Probably other high-load cognitive tasks at hand distracted our attention from our body that had been cooling down for a while already.
Although a simple control mechanism might accommodate the desire for agency in the system from the study participants, as dis-cussed in section 6.6, we think beyond manual control. We imagine a future in which thermal stimuli and ambient intelligence [4] are integrated. Technological applications that leverage context aware-ness and personalization for regulating human body temperature seem then likely. In such applications, it may be desirable that the body is already being warmed up before we think about a need for warming up. A relevant question could then be - how should a thermal stimuli system know when to warm up in order to avoid us thinking about a need to warm up?
7.3
Hybrid materials for aesthetic thermal
artifacts
This section relates mostly to subquestion 2 about the wearability of thermal stimuli. Heat is inevitably transmitted through some medium, and a key contribution this investigation makes is ad-ditional insight about the materiality of such medium. Portable media that transmit heat are currently available, e.g. [16], and the materiality of heat has been addressed to some extent before [23]. However such media render the heating element invisible as it is positioned in between other layers of clothing. We believe there is more scope and opportunity to incorporate heating elements into fashionable garments.
With the advent of conductive threads, heating elements can be-come an artistic expression. By more aesthetic designs, perceptions of suspicion are likely to be avoided. A conductive thread can be seen as a hybrid material, because it can be seen as one component that provides two functionalities simultaneously. That is, provided that a conductive thread is sew in an aesthetically pleasing pattern, it can function as both an element that is designed beautifully and an element that functions as heat producer. We recommend future designers to consider blending features of electrical engineering (= drawing current over a resistant material to generate heat) and fashion design (= beautiful patterns). Minimizing safety risk should be considered by implementing measures that ensure safety by hardware design.
Positioning the wearable on the body deserves attention. How do we position the components of our artifact on the body? In line with [18], we propose that the positioning should match the scenario in which the wearable will be used. The heating pad should
be positioned on a location that naturally matches the objective and activities in that scenario.
In short, we encourage future researchers and designers to con-tinue investigating how the materiality and positioning for thermal stimuli can be designed to balance beauty and functionality.
7.4
Wearing thermal stimuli ”in the field” may
constrain turning attention inwards
As recent studies on thermal feedback covered heat as a potentially beneficial medium to direct awareness of our body via warmth, we briefly contrast findings from this study with prior literature. In line with P10’s and P13’s comments about uncertainty whether heat was felt or not, it may be the case that taking wearable thermal stimuli ”into the wild” as done in our field study constrains reflective activities on bodily sensations.
Shusterman wrote in 2008: ”Attention to bodily feelings can also be enhanced by the strategy of warding off competing interests, since any form of attention constitutes a focalization of conscious-ness that implies ignoring other things in order to concentrate on the object attended” [41]. Warding off competing interest can be done by ”making space”, which is described by Hook et. al [21] as ”to build a secluded space, forming a certain atmosphere or feeling safe, enclosed”. Thus, making space appears to be a re-quirement for turning attention inwards, which heat is particularly well-positioned to do [8, 23]. Turning attention inwards appears to be necessary, in turn, for supporting building bodily awareness [17, 29].
Wearing wearable thermal stimuli outdoor during day to day activities might bring along so many distractions that reflecting on bodily sensations might become complicated. More research might be helpful to understand how thermal stimuli supports bodily awareness in non-reflective settings. A potential future direction could be to around the question: how can wearable thermal stimuli be designed so that it motivates to turn attention inwards?
7.5
Limitations of this study
Although this report mentions the term ”thermal stimuli”, it is rele-vant to mention that this investigation covered only one particular stretch of the dimension of thermal stimuli. That is, the range of temperatures above skin temperature. This study has not covered thermal stimuli coming from elements that are colder than skin temperature. Lack of insight on coldness means that results of this study are only applicable to thermal stimuli above skin temperature. One major limitation to the validity of the findings in this inves-tigation is due to season and the climate zone in which the study was conducted. Studying the experience and applicability of heat in a significantly hotter or colder season in the same location might yield results different from the ones here presented. Extremities such as the Sahara or Arctics might be interesting, not only due to the temperatures but perhaps even more to understand how local inhabitants acclimatize to extreme temperatures. Locals in such outliers might or might not have significantly different sensory experiences for thermal stimuli.
In addition, a deficiency might be observed in the approach for data gathering and making inferences. Study participants sampled from the research lab community were biased in the sense of being
relatively pro-tech. Sampling from another community might yield other conclusions, i.e. more skeptic ones. It can be observed that no structured approach was used to analyze data gathered in the design and testing phases. Not all interviews with study participants have been transcribed. A more structured grounded theory methodology would have been beneficial.
8
CONCLUDING REMARKS
The purpose of this study was to investigate the experiential aspects, opportunities and challenges of designing for thermal stimuli. To an extent, this purpose is achieved. The RtD approach in this study turned out to be useful for addressing this purpose. Although a more systematic inductive analysis would have strengthened these conclusions, the following conclusions are hopefully relevant at an inspirational level.
What are the experiential characteristics of thermal stimuli? Experiencing heat can be characterized as a dimension of sensory experiences which aligns with a range of temperatures. The details of this dimension are described in Section 6.1, and we recommend here that future designers should choose which type of experience they intend to achieve, so that they can heat up to appropriate temperatures.
What are the opportunities and challenges in designing for wear-able thermal stimuli? Overall, the slowness and inertia can be seen as both an opportunity and a challenge, because these features might enable gentle background reminders but can meanwhile limit the complexity of meaning that can be conveyed through heat.
In addition, 2 main opportunities seem to emerge from this study. The first opportunity concerns ambient intelligence systems that enrich human ability to combat cold environments without us being aware of the heat. The second opportunity is about heat as a medium to carry meaning, for which communication theories such as semiotics might support aligning the characteristics of experiencing heat to the meaning that the experience is supposed to achieve.
Challenges are firstly in understanding how much heat to on a body in order to achieve a certain experience. This can be compli-cated as it depends on other tasks at hand and individual acclima-tization to temperatures. Secondly, hybrid materials can support the materiality of heat, but developing and designing wearable hybrid materials that encompass both cold and hot stimuli seems to deserve more attention. Positioning the heat on the body will need to be linked with the function and meaning of the heat, which depends on contexts and purposes of the stimuli. Strengthening bodily awareness via wearable heat systems might only be feasible if awareness is guided to the body via heat in a silent and enclosed place which reduces distractions.
Thus, in summary, what to consider when designing experiences with wearable heat feedback? It needs to be considered that thermal stimuli systems can act as ambient intelligence, as medium to con-vey meaning, and perhaps as both. Choices will need to be made about which experiences are desired to be achieved by choosing appropriate temperatures and positions for thermal stimuli. To leverage the full range of temperatures, wearable cooling technol-ogy should be developed and integrated. Hybrid materials should be investigated further so the full potential of thermal stimuli can
be leveraged. Integrating hybrid materials into garments seems to offer potential to make wearable thermal stimuli fashionable.
With this study, interaction designers, fashion designers and electrical engineers are provided rationales on how to incorporate a primary life need into body-centered computing. We hope that future design enthusiasts appreciate the opportunities of thermal stimuli for enriching our abilities and experiences.
ACKNOWLEDGMENTS
I would like to express my gratitude to my supervisors Florian Mueller and Frank Nack for their excellent guidance. I would like to thank the inspirational and motivational colleagues and wider community of the world-class Exertion Games Lab at the Royal Melbourne Institute of Technology. In addition, all study partici-pants deserve great reward for their willingness to provide valuable inspiration. Finally, I appreciate the safeguarding from Human Research Ethics Committee at the Royal Melbourne Institute of Technology in the form of Ethics Approval HREC/CHEAN 20912.
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