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Tactile Cell Phone Interface Fluid


A high-profile start-up company in California contacted Phantom for help. They had developed a breakthrough tactile cell phone keyboard interface where keys jumped up out of the screen on demand, so that the user could have an interface providing tactile feedback. The patented technology worked by pumping fluid into pouches in an elastomeric (rubber-like) layer. However, it proved extremely challenging to identify a fluid that could meet the many requirements for viscosity, volatility, safety, cost and so on. Most crucially, the refractive index of the fluid had to be an exact match for the elastomer, so that the buttons remained invisible when the screen was in the flat state. They had a terrifically talented team but no chemist, so they called Phantom for help.

The image on the right shows a working example of the tactile cell phone keyboard. In the picture, the buttons are sticking up to provide a satisfying feedback when typing. However, when browsing, the buttons can be made to retract back into the screen where they remain invisible due to the optical properties of the fluid matching those of the screen material. The Wired video shows the screen in action.


The customer provided a list of requirements and I used my knowledge of chemistry to determine the only class of liquids likely to meet the requirements. From there, the next step was to search huge chemical databases manually for an exact match. It was manual, painstaking work but the only way to home in on the best fluid.


Three candidate fluids were suggested and testing revealed them to perform superbly – well beyond anything the client had seen before. They were ecstatic and we went on to do more work together leading to new advances and patents such as WO 2015/031629. That tactile cell phone keyboard patent and other patents, can be found on the Publications & Presentations page.

Tactile Cell Phone Interface

“Chris DeArmitt and his consultancy, Phantom Plastics, are peerless. My company, Tactus Technology, has retained Phantom Plastics for several years, and over that time Chris has consistently and repeatedly found solutions to difficult technical challenges related to all manner of polymer and plastics materials. Often his results are produced within a few days (sometimes even within hours). When asked for advice, his suggestions are grounded in the real world and focus on practical and usually simple-to-test approaches. Dr. DeArmitt’s ideas are novel, and at Tactus we have been able to use them as part of our patent portfolio. He is also a true pleasure to work with, upbeat, focused, enthusiastic, with clarity of thought and a strong network that he is able to draw upon.

This is a glowing testimonial because Chris DeArmitt is that rare find — an amazing resource, both broad and deep, that finds solutions you can use; a kind and kind-hearted person with strong values; and someone you should absolutely hire.”

Dr. Micah Yairi, Co-Founder and CTO, Tactus Technology

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