Open smart ring
A finger-worn health sensor. 2.4 grams. A 15 mAh battery. Everything fights for microwatts.
The open equivalent of the litigious incumbent. We decompose a fully-documented open ring to its real BOM and place each part by cost and differentiation — what is settled, what is cyclical, and where the frontier sits — so the trade is visible before anyone commits to it.
Exploded
Decompose the product into its stack. Each layer is colour-coded: settled, cyclical, or frontier.
Bill of materials
Every part is a real, sourced component from the open baseline — no invented part numbers.
The BLE SoC refreshes on a generation clock (nRF52 → nRF54). Reuse the current part; never design one.
https://www.nordicsemi.com/Products/nRF52840 →A discrete optical analog front-end. The TIA + LED drive + ADC are exactly what an omni-modal biosensing chiplet absorbs.
https://www.goodix.com/en/product/sensors/health_sensor →Mature MEMS commodity. The proof mass can’t fold into CMOS — keep it discrete, reuse as-is.
https://invensense.tdk.com/products/motion-tracking/6-axis/icm-42688-p/ →A second discrete AFE for one slow scalar. Folds into the same biosensing front-end as the PPG.
Flash density refreshes each generation. Reuse the current capacity point.
Commodity curved cell — the fixed energy budget. It’s precisely why moving inference on-die matters.
Settled flex-PCB process. Reuse.
Where openWafer can help
Three of these lines — the PPG optical AFE, the temperature sensor, and their analog conditioning — are separate ICs, each with its own front-end and idle current. The frontier option here is a single omni-modal biosensing chiplet (chopper-stabilised diff-amp + TIA + current-injection) covering PPG, temperature, and bio-impedance on one die — fewer parts, lower idle power, and modalities the discrete stack can’t reach — at the cost and risk of a custom analog design. openWafer can design it, or you reuse the discrete stack and ship now. Which is right depends on the goal: volume, a differentiated product, or a research vehicle. The descent shows the trade; it doesn’t pick for you.