Patina Engraver: Visualizing Activity Logs as Patina in Fashionable Trackers

CHI 2015, April 18–23, 2015, Seoul, Korea – Paper presentation

Best Paper of CHI


Moon-Hwan Lee, Seijin Cha, Tek-Jin Nam


Despite technological improvements in commercial activity trackers, little attention has been given to their emotional, social, or fashion-related qualities, such as their visual aesthetics and their relationship to self-expression and social connection. As an alternative integrated approach incorporating HCI, fashion, and product design, our project made use of the characteristics of patina to improve activity trackers as fashionable wearables. We developed the Patina Engraving System, which engraves patina-like patterns on an activity tracker according to a user’s activity logs. Using a piercing technique, the patina of activity logs has been made abstract, visually rich, gradually emerging, and historically accumulated. During the field trial, we found that the patina motivated the participants to increase exercises for engraving aesthetic patinas. A tracker with patina triggered spontaneous social interactions in face-to-face situations. The participants also cherished the trackers that held their own history. Based on the field trial, we discuss design implications for utilizing patina in designing future fashionable technologies.


Activity tracker; patina; fashion; digital fabrication.


Research Approach

Nowadays, in the market, there are plenty of activity trackers for monitoring physical activity. And in the HCI field, activity log visualization has been one of key issues for motivating users.  However, from the customers perspective, one of the important aspects is that they are personal fashion items.  To design better tracking system, we aim to integrate activity log visualization with an understanding of activity trackers as fashionable wearables.


Patina-like Visualizing Techniques and Materials

To simulate patina, We considered several fabrication techniques and compared whether they are suitable to express the characteristics of patina. Finally, we found possibilities in piercing technique Like stippling art works and tattooing.



Patina Engraving System


We designed Patina Engraving System consisting of the Patina Tracker and the Patina Engraver.  In this system, users’ activity logs are periodically saved to the local computer which is connected to patina engraver. When the Patina Tracker is placed on the Patina Engraver, the engraver identifies the user and loads activity logs. Then, the local computer sends pattern codes the Patina Engraver.


Hardware of Patina Tracker


We developed The Patina Tracker that used three-layered material we developed in the wristband part. To fasten the band, magnets were attached inside. As a tracking sensor, we utilized the sensor part of Fitbit Flex. Additionally, an RFID tag was attached inside the band to identify the participant’s ID.


Hardware of Patina Engraver


The Patina Engraver mainly consists of two stepper motors and a piercing unit. The piercing unit is moved in the XY-plane and drives the needles up-down by the solenoid. The rack at the bottom is used to place a tracker for engraving.

As the piercing unit repeatedly drives the needle in and out of the surface, the needle leaves small dots on the surface. When the needle reaches The surface of trackers, Paint layer is peeled and PVC sheet sticks out below the paint layer.


Patterns on Patina Tracker


Layout of Patterns on patina tracker was also designed. Firstly, we selected (i) activity logs such as steps, active time (minute), activity calories, time in bed (minute), and total walking distance as the source data for engraving patina. Then, we considered (ii) shapes and physical location for expressing the each log as patina. After exploring several alternatives, the pattern layout on an activity tracker was decided by considering noticeability and visual aesthetics.


Field Study Setting & Result


We conducted a field study in the wild to understand the impact of patina-like visualization. We focused on functional, emotional, and social aspects of tracking experience. We recruited a group of participants in the same sports club. During the field trial, every week the participants had to engrave twice and we conducted Individual & Group Interview.


As a result, we found four impacts. Two of them were related to impacts on activity monitoring. Another two were related to impacts on trackers as fashion items.

  • Wondering about What Patina Means & Past Activities
  • Feeling Pressure for Engraving Aesthetic Patina
  • Having Spontaneous Co-located Interaction
  • Crafting a Symbolic Object that Holds One’s Own History