Figure 1: Conceptual design ofPairRing system. A user wearsPairRing on the index finger andput on the smartwatch on the samehand. By rotating PairRing withthumb, the user can controlvertically aligned items onsmartwatch.

PairRing: A Ring-Shaped RotatableSmartwatch Controller

Jungmin ChungHCC Lab, GSCSTSeoul National Universityjungminchung@snu.ac.kr

Bongwon SuhHCC Lab, GSCSTSeoul National Universitybongwon@snu.ac.kr

Changhoon OhHCC Lab, GSCSTSeoul National Universityyurial@snu.ac.kr

SoHyun ParkHCC Lab, GSCSTSeoul National Universitysohyun@snu.ac.kr

Permission to make digital or hard copies of part or all of this work for personal orclassroom use is granted without fee provided that copies are not made or distributedfor profit or commercial advantage and that copies bear this notice and the full citationon the first page. Copyrights for third-party components of this work must be honored.For all other uses, contact the owner/author(s).

Copyright held by the owner/author(s).CHI’18 Extended Abstracts, April 21–26, 2018, Montreal, QC, CanadaACM 978-1-4503-5621-3/18/04.https://doi.org/10.1145/3170427.3188590

AbstractSmartwatch users often report usability problems despiteits handiness and convenience. Fingers often block thescreen, and both hands are often required to operate thegadget. To address these issues, we present PairRing, aring-shaped rotatable smartwatch controller. PairRing al-lows users to scroll up and down listed items by turning thering on their index finger with their thumb. To determine theoptimal ring shape and rotation speed, we designed andconducted a user study and report the results. We foundthat (1) users could perform tasks better with the angularring prototype; (2) the rapid rotation speed was better suitedfor browsing ordered lists; and (3) overall, participants werepositive about the feasibility of the prototype. We concludewith a discussion on the design implications of PairRing aswell as its future applications.

Author KeywordsSmartwatch; Ring-shaped Controller; Wearables

ACM Classification KeywordsH.5.m [Information interfaces and presentation (e.g., HCI)]:User Interfaces-Input Devices and Strategies.

IntroductionRecently, smartwatches have become one of the most com-mon electronic gadgets. However, the fact that the user

CHI 2018 Late-Breaking Abstract CHI 2018, April 21–26, 2018, Montréal, QC, Canada

LBW635, Page 1

must wear the watch on one wrist and operate it with theother hand limits the ease of manipulation and accessibil-ity of the device. This sets the smartwatch apart from othergadgets, such as smartphones and tablets, in terms of itsunique interaction design. Many HCI researchers have ad-dressed the issue and suggested employing various inter-action techniques [3, 5, 4, 9, 11, 13].

Figure 2: PairRing andSmartwatch system : (a) VirtualSmartwatch Interface and (b)PairRing Prototypes. The virtualsmartwatch and additionalinformation are depicted in thesmartphone interface. Users fastensmartwatch on their wrist. And theusers wear PairRing in their indexfinger of the same hand.

Still, many smartwatch users report problems. The limitedscreen size of the smartwatch often causes control errorsthat interfere with user intent [2]. In addition, users mustwear the watch on one wrist and operate it with the otherhand, forcing them to use both hands. This could be a bar-rier not only for people with disabilities but also for averageusers who use their smartwatches while in transit or whilecarrying personal belongings.

To address the aforementioned issues, we present Pair-Ring, a ring-shaped rotatable controller for operating smart-watches with one hand. Users can control PairRing by turn-ing it with their thumb, which enables an intuitive interactionwith the smartwatch (Figure 1).

In this work, we designed and evaluated the feasibility ofthe PairRing prototype. We explored the shape and the ro-tation speed of the ring prototype to determine the mostappropriate conditions for easier and more convenient use.Users were presented with two different shapes (circular vs.angular) and two different rotation speeds (slow vs. rapid).They performed tasks where they were measured in termsof the time taken for item navigation. They evaluated theusability of the prototype in the survey and completed shortinterviews. Our key findings are as follows. (1) Users couldmanipulate their smartwatches more quickly and easily withthe angular type of the PairRing prototype. (2) They per-formed better with the rapid rotation speed for the giventasks. (3) Participants were positive with the idea of using a

ring-shaped device for controlling their smartwatch.

The contributions of our study are below:

• We designed and implemented PairRing, a novelring-shaped controller for a smartwatch that can beoperated with one hand that is wearing the watch.

• We evaluated the usability and feasibility of the Pair-Ring prototype and suggested design considerations.

• From the interview, we identified that PairRing systemcould be applied to other devices and contexts.

Related WorkVarious input methods for improving interactions with smart-watches have been studied, such as kinematic devices [11],built-in or additional sensors [5, 9], cameras [3], finger-mounted devices [10] and smartwatch’s bezel [13]. Har-rison et al. suggested an additional device that can beworn on a user’s finger, enabling in-air control of the smart-watch [4]. Although these previous studies explored newways of manipulating the smartwatch interface withoutblocking it, they still required users to use both hands.

Meanwhile, many researchers have studied using ring-shaped controllers as new input methods for smart de-vices, such as optical sensors [12] and cameras [7]. Someused infrared sensors to measure hand and finger move-ments [8], while others investigated the possibility of inputusing pressure sensors [6]. Notably, several studies usedring-shaped rotating devices as an input method. For exam-ple, Nenya [1] used magnets, and iRing [8] used skin strainand distance sensors. Although these have identified newpossibilities in terms of using the ring as an input methodwith various sensors, they have not yet explored the rotatingof the device to control the interfaces of smartwatches orother smart devices.

CHI 2018 Late-Breaking Abstract CHI 2018, April 21–26, 2018, Montréal, QC, Canada

LBW635, Page 2

PairRingPairRing is a new way of controlling smartwatches. It is aring-shaped, rotatable controller worn on the index finger ofthe same hand with which users can manipulate the smart-watch by turning it with their thumb. Figure 1 shows theresearch prototype of PairRing.

Design PrototypeThe PairRing system operates on two parts: a virtual smart-watch user interface on a smartphone and a ring controller.(Figure 2)

PairRing has three components: the upper body, the lowerbody, and a pair of magnets between them (Figure 3). Asusers rotate the ring, the magnets change the magneticfield around the system, and then the movement of thering is detected by a sensor in the paired smartphone. Thebodies of the ring were made using a 3D printer, betweenwhich 3mm X 3mm size and N42-grade neodymium mag-nets were inserted. The prototype is diametrically magne-tized.

Figure 3: (a) The upper body ofPairRing; (b) The magnets; and (c)The lower body of PairRing. Themagnets fit in the upper and lowerbody of the prototype.

Figure 4: The shape of thePairRing and rotation per itemmovement speed. The ring has twotypes of shape: angular andcircular. The users can move thecursor by rotating the ring 90degree in slow and 45 degree inrapid.

The virtual smartwatch user interface was designed bysimulating the smartwatch interface on the center of thescreen of a smartphone (Figure 2). In the blank space ofthe screen, additional information (e.g. task type, opera-tion speed, timer) is displayed as a dashboard. A SamsungGalaxy S7 was used as the apparatus for the experiment.When a user fastens the smartphone with a band on theirwrist, it is almost as if the user is wearing a real smart-watch.

Ring Shape and Rotation SpeedIn the process of designing the prototype, we consideredtwo factors, ring shape and rotation speed, and devised twodifferent styles for each factor (Figure 4).

• Ring Shape: There are two ring shapes: circular andangular. We chose an octagonal shape for the angu-lar one, which helps to facilitate the user’s holding ofthe ring’s surface [6].

• Rotation Speed: There are two operation speeds:slow and rapid. With the slow speed, users couldmove the cursor one item up and down on the screenby rotating the ring for 90 degrees. On the otherhand, with the fast speed, users could move the cur-sor up and down by rotating the ring for 45 degrees.

User StudyTo evaluate the feasibility of PairRing and identify the mostappropriate shape and rotation speed for operation, we de-signed and conducted a user study where users performeda given task and participated in a survey and an interview.

TaskWe created an application that worked on the smartwatch(Figure 5) for the experiment. The application providedusers a list of 26 words. Users could move the cursor andnavigate the items by rotating PairRing with their thumb asshown in Figure 1. Participants were asked to find targetitems using the blue cursor (Figure 5) by rotating the ringcontroller. we measured the time taken for a user to locateeach given target word appeared on the dashboard amonga list of word items.

Participants and ProcedureA total of 16 participants performed the task (6 female).Their average age was 30.1 (SD=4.24). The participantsperformed 12 browsing trials (two shapes X two rotationspeeds X three iterations). All trials were presented in arandom order. Prior to trials, participants had enough timeto familiarize themselves with the system. We also evalu-ated the usability of each condition by asking the partici-

CHI 2018 Late-Breaking Abstract CHI 2018, April 21–26, 2018, Montréal, QC, Canada

LBW635, Page 3

pants to answer the System Usability Scale (SUS) using the7-point Likert scale. After completing all trials, participantswere invited for a post-hoc interview.

Figure 5: Our smartwatchapplication. It consists of total 26words, each of which is as easynoun starting with a letter from A toZ. All words are arranged in ahierarchical order. The bluehighlight acts as a cursor that theuser can move around. The cursorgoes up and down by turningPairRing.

Data AnalysisWe conducted both quantitative and qualitative analyseson collected data. First, we conducted a 2X2 two-way RMANOVA on the time and usability scores. We transcribedand reviewed the interviews by tagging them by keywordsand employing a thematic analysis.

Quantitative AnalysisWe have found statistically significant effects on time andusability of our PairRing system.

TimeA total of 192 observations (16 participants X 2 shapes X 2rotate speeds X 3 trials) were analyzed. We conducted two-way RM ANOVA test and identified significant effects forshape (F(1,188) = 3931.06, p < 0.01) and rotation speed(F(1,188) = 256.79, p < 0.01) on time. We also found asignificant two-way interaction between them (F(1,188)= 33.72, p < 0.01). This shows that the time consumed isshorter with angular shape and rapid rotation speed. (Fig-ure 6(a))

UsabilityWe collected 64 user ratings (16 participants X 2 shapesX 2 rotate speeds). We found significant effects for shape(F(1,60) = 303.43, p < 0.01) and rotation speed (F(1,60)= 47.30, p < 0.01) on the usability of our system. How-ever, there was no significant interaction effect betweenthe two factors (F(1,60) = 1.53, p = 0.22). The result sup-ports higher usability with angular shape and rapid rotationspeed. (Figure 6(b))

Qualitative AnalysisMany users reported that the angular-shaped ring was easyto hold, while they had mixed opinions for speed prefer-ence. Overall, they found PairRing useful, intuitive, and ap-plicable.

The Angular-shaped Ring is Easy to HoldParticipants said the angular-shaped ring offered betterhaptic feedback than the circular-shaped ring, as it had aflat surface. P3 said, “I like this flat surface. While rotatingthis device, it was more comfortable and I could rotate itbetter.” P7 also said, “The circular-shaped ring had no edgeto pull or push on, so it was difficult for me to control.”

Speed Preference is Task-DependentDespite the findings from the statistical analysis, someusers reported that they did not always preferred the rapidrotation speed. While the rapid speed was suitable forbrowsing a longer list of items, the slow speed was moreappropriate when they tried to apply a fine change in locat-ing the item on the screen. P12 said, “In the rapid condition,even if I only moved the device a little bit, the switching ofthe item occurred too quickly. So, if I had to control it pre-cisely, I would prefer the slow mode to the rapid mode.” P2said, “For tasks requiring a lengthy exploration, such assearching long lists, I think the rapid mode is better, but Iwould prefer the slow mode for tasks that require a smalleritem selection.”

PairRing is Useful, Intuitive, and ApplicableMost participants said that PairRing was very useful andintuitive, and could be applied to other contexts. Someof them even considered PairRing a potential solution forfat finger problem. P6 said, “Because this interaction sys-tem can be controlled by only one hand, now I can see mysmartwatch without blocking the screen.” P8 said, “I lovethis way of moving the cursor up and down. It is very in-

CHI 2018 Late-Breaking Abstract CHI 2018, April 21–26, 2018, Montréal, QC, Canada

LBW635, Page 4

tuitive.” P9 also added, “I’d like to use PairRing for otherdevices and situations as well. I think it would be useful if Icould connect it with my television. It would help me switchchannels easily.”

Design ConsiderationsBased on the findings from the user study, we discuss thedesign implications of PairRing.

Figure 6: The mean of time taken(a) and usability scores (b) ofparticipants in each shape androtation speed condition. (a) showsthe angular/rapid rotation speedcondition required the shortestamount of time. Likewise, (b)indicates the same conditionrecorded the highest usabilityscore.

Double-Sided SurfaceOur study participants showed a strong preference for theangular-shaped prototype of PairRing. That the outer andinner sides of the ring are different can effectively servetwo purposes. The inner side of the ring, which is circularas a usual ring is, conveniently suits the finger. The outerside of the ring, which is angular, provides a flat surface onwhich users can apply input in a more convenient manner.We believe this creates a novel interaction space for HCIresearchers to employ yet to be explored input and controlmethods on a smart device.

Speed AdjustmentWhile we identified that users generally preferred the rapidrotation speed, they reported that the slow speed servedthe purpose better in some trials. We find that while userswould naturally want to navigate items faster, they wouldalso strongly prefer to avoid control errors. More specifi-cally, in contexts where users explore a lengthy list of items,speed adjustment should be equipped in system settings sothat users can serve their needs on their own.

Device ConnectivityPost-hoc interviews suggest that paired interaction can beapplied to various smart device usage contexts. For exam-ple, users can use the ring-shaped device to control otherdevices in distance such as TV and smart screens. Theycan also make adjustments on wearable devices (e.g. mod-

ulate intensity of sunglasses or hearing aids), and authenti-cate themselves (e.g. substitute for car key).

Limitations and Future WorkOur work is not without limitations. First, we did not utilizea smartwatch for our experiment. Also, the task only per-tained to item navigation, for which we are now consideringother use case scenarios. In future work, we will implementthe system on a smartwatch device paired with our pro-totype. We plan to make improvements on the system tobetter function as a controller. We will design various func-tions (e.g. click, swipe etc.) and applications such as con-trolling music playlists, locating on a map, etc. We aim toacquire a higher level of usability when employing a typicalsmartwatch interface, and compared with other ring shapeddevices. Moreover, as more and more devices are con-nected (i.e. Smart Home), we will explore how a simple ringcontroller may be applied to a variety of smart devices andapplications at home, office, and work settings.

ConclusionWe designed and implemented PairRing, a ring-shapedsmartwatch controller. To gauge its feasibility, we con-ducted a user study consisting of a set of trials, a surveyquestionnaire, and a semi-structured interview with 16 par-ticipants. We found that users could potentially manipu-late their smartwatch more accurately and quickly with theangular-shaped PairRing prototype than the circular one.They could perform the task better with the rapid rotationspeed, albeit having mixed opinions on speed preference.They were positive about the idea of using PairRing forcontrolling their smartwatch and other smart devices. Wepresent design suggestions for a ring-shaped controller forsmart devices, which we hope to contribute to designingnew interaction spaces and techniques for smartwatch con-trollers and improving usability of existing smart devices.

CHI 2018 Late-Breaking Abstract CHI 2018, April 21–26, 2018, Montréal, QC, Canada

LBW635, Page 5

REFERENCES1. Daniel Ashbrook, Patrick Baudisch, and Sean White.

2011. Nenya: subtle and eyes-free mobile input with amagnetically-tracked finger ring. In Proc. of the SIGCHIConference on Human Factors in Computing Systems.ACM, 2043–2046.

2. Minhee Chae and Jinwoo Kim. 2004. Do size andstructure matter to mobile users? An empirical study ofthe effects of screen size, information structure, andtask complexity on user activities with standard webphones. Behaviour & information technology 23, 3(2004), 165–181.

3. Xiang’Anthony’ Chen, Julia Schwarz, Chris Harrison,Jennifer Mankoff, and Scott E Hudson. 2014. Air+touch: interweaving touch & in-air gestures. In Proc. ofthe 27th annual ACM symposium on User interfacesoftware and technology. ACM, 519–525.

4. Chris Harrison and Scott E Hudson. 2009.Abracadabra: wireless, high-precision, and unpoweredfinger input for very small mobile devices. In Proc. ofthe 22nd annual ACM symposium on User interfacesoftware and technology. ACM, 121–124.

5. Gierad Laput, Robert Xiao, Xiang’Anthony’ Chen,Scott E Hudson, and Chris Harrison. 2014. Skinbuttons: cheap, small, low-powered and clickablefixed-icon laser projectors. In Proc. of the 27th annualACM symposium on User interface software andtechnology. ACM, 389–394.

6. Hyunchul Lim, Jungmin Chung, Changhoon Oh,SoHyun Park, and Bongwon Suh. 2016. OctaRing:Examining Pressure-Sensitive Multi-Touch Input on aFinger Ring Device. In UIST. ACM, 223–224.

7. Suranga Nanayakkara, Roy Shilkrot, Kian Peen Yeo,and Pattie Maes. 2013. EyeRing: a finger-worn input

device for seamless interactions with our surroundings.In Proc. of the 4th Augmented Human InternationalConference. ACM, 13–20.

8. Masa Ogata, Yuta Sugiura, Hirotaka Osawa, andMichita Imai. 2012. iRing: intelligent ring using infraredreflection. In Proc. of the 25th annual ACM symposiumon User interface software and technology. ACM,131–136.

9. Hongyi Wen, Julian Ramos Rojas, and Anind K Dey.2016. Serendipity: Finger gesture recognition using anoff-the-shelf smartwatch. In Proc. of the 2016 CHIConference on Human Factors in Computing Systems.ACM, 3847–3851.

10. Haijun Xia, Tovi Grossman, and George Fitzmaurice.2015. NanoStylus: Enhancing input on ultra-smalldisplays with a finger-mounted stylus. In Proc. of the28th Annual ACM Symposium on User InterfaceSoftware & Technology. ACM, 447–456.

11. Robert Xiao, Gierad Laput, and Chris Harrison. 2014.Expanding the input expressivity of smartwatches withmechanical pan, twist, tilt and click. In Proc. of theSIGCHI Conference on Human Factors in ComputingSystems. ACM, 193–196.

12. Xing-Dong Yang, Tovi Grossman, Daniel Wigdor, andGeorge Fitzmaurice. 2012. Magic finger:always-available input through finger instrumentation.In Proc. of the 25th annual ACM symposium on Userinterface software and technology. ACM, 147–156.

13. Xin Yi, Chun Yu, Weijie Xu, Xiaojun Bi, and YuanchunShi. 2017. COMPASS: Rotational Keyboard onNon-Touch Smartwatches. In Proc. of the 2017 CHIConference on Human Factors in Computing Systems.ACM, 705–715.

CHI 2018 Late-Breaking Abstract CHI 2018, April 21–26, 2018, Montréal, QC, Canada

LBW635, Page 6