Hot-Dot: An open thermal haptic interface for smartphones

Hot-Dot thermal haptic finger ring connected to a smartphone

AI-generated semi-slop image to show the concept - it's going to be close to this - I promise!

Principle of Operation

Hot-dot is a thermal haptic interface that converts content from a smartphone screen to thermal feedback. It uses the smartphone CPU to analyse the content under a user's finger and converts the region of interest to thermal signals, which are sent to an MCU that drives the microheaters.

Wearable finger-band: A Kapton-based ring with an array of SMT thermistors working as heaters, optional photodiodes, RP2040, peripheral electronics and USB-C.
Android script: Reads screen content around the touched area, translates it to Braille or hybrid texture modes, and communicates with the finger-band.

Technical Specifications

Hardware
Actuators	2x4 Array SMT thermistors as microheaters
FETs	Small-footprint n-type MOSFETs driven from VUSB
Firmware
MCU	RP2040
Protocol	USB CDC Serial/UART
Software
Android	Native or simple framework
MCU	Raspberry Pi Pico SDK
PCB Design	KiCad