Food and flavors are integral to our existence in the world. Nonetheless, taste remains an under-explored sense in interaction design. We present Füpop, a technical platform for delivering in-mouth flavors that leverages advances in electronics and molecular gastronomy. Füpop comprises a fully edible pouch placed inside the mouth against a cheek that programmatically releases different flavors when wirelessly triggered by a focused ultrasound transducer from outside the cheek. Füpop does not interfere with activities such as chewing and drinking, and its electronics may be integrated into devices already used near the cheek, such as mobile phones, audio headphones, and head-mounted displays. Füpop’s flavors are from “real foods,” not ones imitated with synthetic reagents, providing authentic, nutritive flavors. We envision that with Füpop, flavors may be synced to music, a phone call, or events in virtual reality to enhance a user’s experience of their food and the world.

Skin-based electronics are an emerging genre of interactive technologies. In this paper, we leverage the natural uses of lotions and propose them as mediators for driving novel, low-power, quasi-bistable, and bio-degradable electrochromic displays on the skin and other surfaces. We detail the design, fabrication, and evaluation of one such “Lotion Interface,” including how it can be customized using low-cost everyday materials and technologies to trigger various visual and temporal effects – some lasting up to fifteen minutes when unpowered. We characterize different fabrication techniques and lotions to demonstrate various visual effects on a variety of skin types and tones. We highlight the safety of our design for humans and the environment. Finally, we report findings from an exploratory user study and present a range of compelling applications for Lotion Interfaces that expand the on-skin and surface interaction landscapes to include the familiar and often habitual practice of applying lotion.