Droplet is both a water filter and a portable water quality meter. It is attachable to any standard PET bottle, making it very flexible. The water quality meter measures multiple parameters, both before and after filtering, so you can both learn the quality of your water and see the effect of filtering it!



The journey started with discovering a new perspective of PET bottles.PET bottles can be used to store and transport a multitude of things, fluids being maybe the most popular choice. There are limits to the amount of temperature and pressure your bottle can handle, but apart from that, use your imagination!

We explored the intended use and redefined the meaning of PET bottles by creating a mindmap and observing interaction around PET bottles. The experience of discovering a new perspective of PET bottles was translated into several sketches and ideas.


Design Workshop

There is one interesting characteristic of PET bottles which is the design of the bottle neck which can be attached to a cap with specific thread design. At the same time, we found that there were several inventions around plastic bottles which involved a water filter technology. The intersection of those two inspired us to misuse PET bottle by creating a detachable item which can be easily used as a water filter.

A design workshop helped us imagine the possible design of the product. It also helped in the exploration of designing the interactive technology feature.



Creating a prototype was conducted as a proof of concept of the design. A 3D design was made and a 3D model of the cap design was printed.

2 sensors are responsible for detecting the water quality each before filtering and after filtering process. The sensors measure pH, conductivity, dissolved oxygen (DO), temperature, salinity, and total dissolved solids (TDS).

Droplet works together with your smartphone; your handheld takes care of data processing and the Droplet App gives you a visualization and explanation of your test results. Droplet is designed as a crowdsourcing initiative, letting you automatically publicise your test results for the benefits of other people. View the prototype here


Final result

A project for course DH2628 - Interaction Design as a Reflective Practice

KTH Royal Institute of Technology, Stockholm


Edvard Ahlsén (edvarda [at] kth.se)

Adrian Benigno Latupeirissa (ablat [at] kth.se)

Ela Yudhanira (elayu [at] kth.se)