The Tech Blog

It’s CES week, and as usual, I wanted to have a look at the wackiest tech products put out this week and figure out the tech behind it. This year that pick is iPolish, the press-on nails that change colour with a phone and a small wand. Search online for the product demo videos, it’s pretty good.

If you strip away the fancy stuff, it’s a form of e-paper screen. They call it a screen with “Electrophoretic nanopolymers”. Electrophoretic just means charged pigment particles move in a fluid when you apply an electric field. The pigment you pull to the top is the colour you see. Once set, it is stable and needs no refreshing or power to retain the colour. I have previously written about the ePapers and how it works in detail if you want to read more about it.

I looked into the patents filed. It describes a stack that feels like a tiny curved display. There is a nail blank, transparent electrode, microcapsule pigment layer, and a patterned backplane electrode with traces. It comes with a unit called as wand which is controlled via BLE from your phone app. You choose a shade, but it’s stored as a colour file that is basically a voltage list. For the movement of particles (for colour change) you can’t just give a DC voltage, You typically need a balanced pulse sequence in the ±15 V to ±20 V range to avoid ghosting and charge trapping. The wand pushes that waveform through metal contacts on the back of the nail. Contacts are like a programming header to configure and then retain the colour.

Pricing seems to be around $99 and after that around $3.5nail for replacement. The website talks about the nail being active only for 30 days. I’m not fully sure if that’s a real electrochemistry or materials lifetime limit OR it could be purely be the company chasing the subscription revenue model, which I would say is a downer.

Anyways interesting tech. The core idea is solid. If they can manufacture a curved, addressable e-paper laminate this cheaply, the obvious next step is larger form factors. Colour changing dresses probably…

Last month, Bluetooth Core 6.2 made a change I have wanted for years. It solves a long-standing pain point in Bluetooth LE when you care about real-time response. Back when I was building low latency MIDI controllers at ACPAD, we were operating in the BLE 4.0 era. On that, I could move plenty of bits, but not shorter data faster. The main issue was the connection timing.

In BLE, a connected link wakes up in repeating connection events. The connection interval is the time between those events. Until 6.2, the minimum connection interval was 7.5 ms, which means your worst case packet can wait 7.5ms for the next connection, even before protocol overhead delays. For tight MIDI timing in real time instrument playing, this delay feels like a sound lag for professional musicians.

BLE 6.2 introduces Shorter Connection Intervals(SCI), pushing the minimum down to 0.375 ms when both devices support it. This means you can send small packets of data faster. In practice, that means you can get a polling rate over 1kHz. This is a big deal of HID devices like mouse. Gamers don’t use wireless BLE mouse for this exact reason. You will see a large boom in wireless BLE mouse and fall in the mouse with 2.4GHz USB dongles where this limit is not applicable.

Please note that your raw on-air speed is still based on the 2M LE PHY and that has not increased. Shorter intervals just reduce waiting time between opportunities to send small packets.

BTW, do not treat the smallest interval as a default setting. More transfers mean more battery loss. A better option is adaptive timing, meaning run a longer interval while idle, then negotiate a shorter one only during interaction, and return to a longer interval when activity stops. A 6.2 connection still starts at ≥7.5 ms and only then negotiates shorter intervals.

BLE 6.2 can mark some input packets as “flushable”. If packet loss conditions delays them, BLE can drop the old ones instead of sending them late. Good for mice or MIDI, as the late updates feel worse than a missed one.