Doug Kanter
Engin Ayaz
Tak Cheung


HeartWave is a tabletop device that uses water ripples to visualize the heartbeat of two people at once.

Introduction to Physical Computing

HeartWave visualizes your pulse, turning heartbeats into waves. One or two people can activate HeartWave. To begin, users hold their hands against sensors on the side of the tank. Each heartbeat briefly powers a magnet, pulling a fin and generating a wave. This simple interaction quickly becomes mesmerizing as ripples emanate, override, clash and dissipate. Variations in liquid and lighting allow for a range of unique HeartWave experiences. In a poetic sense, this project becomes the extension of its viewer as they see and feel their heartbeat drawn out into this familiar medium.

We are proud that the project was highlighted in Make Magazine Blog recently ( and are excited about the prospect of sharing our work with a wider audience at the Winter Show.

Tak, Doug and I created HeartWave for our Intro to Physical Computing media controller assignment. After a week of exploration, we converged on the idea of visualizing heartbeat patterns using water as our medium. We became interested in exploring wave generation as a means of making heartbeats subtly visible. With three weeks of design and production iterations, we created a custom-built box that uses two people\'s heartbeats as input and generates waves as outputs . We are quite pleased with the interaction that this product produces, especially using various liquids and lighting conditions. Additional positive feedback from our peers encouraged us to propose this project for the Winter Show.

For those who finds tranquillity in reflecting ponds.
For those who'll be enchanted by the metaphysical extension of themselves in water.
For those who finds wonderment in biofeedback and seeing their own heartbeat.
For those who'll appreciate slowing down the pace of time.

User Scenario
An individual approaches HeartWave, and places his/her hands onto the metal plates that are used to read the heartbeat. As they wait for the device to register the heartbeat, which takes a few seconds, the light underneath the fluid surface slowly brightens, providing visual feedback and occupying the use. Then the waves start being generated by the fin. Intrigued by this device, another person approches and puts his/her hand on the other side of HeartWave. Another set of waves are generated, leading to emergent complex visual patterns. After about 20-30 seconds of interaction, the actors leave and tell their friends to try out this mesmerizing experience - one that feels far different in first person compared to one of a spectator.

A user scenario video can be found here:

HeartWave is a 2.5 x 1.5 foot box that is constructed from a plexiglass frame with blue foam and black plastic, coated with Magic-Smooth polymer finish. On four corners, there are pairs of metal plates, on which the actor places their hands. The heartbeat reading is done via a Polar chip, which sends data digitally to an Arduino. On the output side, a 12V magnet is activated using a TP120 transistor. This magnet pulls a plastic fin which contains a metal piece at its midpoint.

This project was developed as a Media Controller midterm, and is fully functional. Possible enhancements include an interactive lighting setup, one that responds to hand placement as well as incorporation of sound feedback. The team is committed to execute on these enhancements if the project were to be selected for the Winter Show.

We have a list of lessons learnt, documented in our blog (see URL above). Below is an abridged summary. Overall, the project was a great learning experience, both in terms of technical and collaboration-related challenges.

- Buying Sensors: We began by trying to build our own pulse oximeters to sense each heart beat. After two frustrating weeks, we were still getting inconsistent and noisy readings (detailed here). We certainly gained a lot of good experience with circuits and hardware. But in the end, this new found knowledge did not translate into good input data. Our input problem was holding up progress on the rest of project. Fortunately, ITP Chair Dan O’Sullivan rescued us with an off-the-shelf Polar heart rate circuit board. Unlike our homemade devices, which gave us analog information, the Polar solution registered pulse in digital form. With the input side sorted, and we could attend to other parts of the project.
Lesson learned: You need to keep perspective on getting the whole project built. If one aspect of the build is not working, you need to consider other solutions to keep things moving forward.

- Virtual Model before Physical Model: From past experience, we have learned that it saves time and money to first iterate and modify in the world of bits before moving on atoms. This HeartWave project proves this point. We developed a reasonably detailed SketchUp model for the tank and made multiple design decisions based on that model. It was great for determining all the technical and aesthetic issues throughout the rest of the physical build. It allowed us to determine how to cut the majority of the components (minus the bottom plexi layer and the fins). Even so, using SketchUp we failed to consider later details including where to hide the Arduinos, place the lights and put a label for the project.
Lesson learned: The devil is in the details. Taking an hour to think through the final presentation can save you many hours later.

- Dimensions: We used a laser cutter for most of the large plexi sheets that form the box. Our tank design was too big for ITP’s laser cutter, so we had to use the one at Canal Plastics. They did a great job, though not at a bargain price. If we had kept our design within the constraints of ITP’s laser cutter, we could have saved money.
Lesson learned: Ambitious designs are expensive.

- Laser Cutter > Craftsmanship: There is really no reason to go with manual cutting for most parts. The time saved and higher quality of laser cutter parts beyond compare.
Lesson learned: We could have saved even more time cutting the fins and small plexi components using the laser cutter.

- 12V != 5V (or how to fry an expensive chip): Pay attention when you are using multiple power sources! I mistakenly wired the Polar board with 12V, which fried the chip ($70 loss!).
Lesson learned: Create a system to distinguish power lines of varying voltages.