How the Hiyd Microsuction Sensor Works: The Engineering Behind the Attachment

Most wearable health trackers solve the attachment problem the same way: they become the watch. The device is the band, the case, the whole thing. If you want the data, you wear their hardware instead of yours.

Hiyd takes a different approach. It is a biometric sensor that attaches to the back of a watch you already own, sits flush against the caseback, and collects heart rate, HRV, sleep staging, movement, calories burned, VO2 max estimation, and nutrition data without asking you to give up the watch you already wear.

The mechanism that makes this possible is microsuction. Understanding how it works explains why the attachment is both secure and residue-free, and why it is physically distinct from every other attachment method used in wearable health technology today.

What Microsuction Actually Is

Microsuction is a material technology, not a mechanical pump or pressure seal. The surface of a microsuction pad is covered in thousands of microscopic open cells, each acting as a tiny cup that conforms to a flat or gently curved surface and holds through friction and surface contact rather than through adhesive chemistry or magnetic force.

When you press the Hiyd sensor against a watch caseback, those cells make contact across the surface and create a distributed grip. No glue. No magnets. No adhesive film that transfers to the caseback when you remove the sensor. The hold comes entirely from the material's physical structure against the watch surface.

This matters for watch owners in a specific way. Mechanical watch casebacks are finished surfaces, often polished, brushed, or engraved. Any attachment method that leaves residue, requires adhesive, or introduces magnetic force is a non-starter. Microsuction avoids all three.

The Physical Specifications

Hiyd is under 3mm thick, 30mm wide, and weighs 7 grams. At those dimensions, it sits behind the caseback without adding meaningful bulk to the wrist profile. The sensor is designed to fit 95% of mechanical watch casebacks, and Hiyd backs that with a guaranteed fit or money back.

The thinness is not incidental. A sensor that added significant height to the caseback would change how the watch sits on the wrist, affecting both comfort and the optical sensor's contact with skin. Keeping the profile under 3mm preserves the wearing experience of the original watch.

Why Non-Magnetic Matters for Mechanical Watches

Mechanical watch movements are sensitive to magnetic fields. A magnetised rotor or balance wheel can cause a movement to run fast, slow, or stop entirely. This is a known and documented problem for watch owners who carry phones, work near electronics, or wear certain accessories.

Hiyd uses no magnets in its attachment mechanism. The microsuction grip is purely mechanical contact. Attaching and removing the sensor does not expose the movement to any magnetic field, and there is no risk of magnetising the movement over time.

For owners of automatic or manual-wind watches, this is not a minor detail. It is the difference between a sensor that is compatible with their collection and one that is not.

Battery, Charging, and Daily Use

The sensor runs for 30 hours on a single charge and supports 15-minute quick charging on its cradle. The cradle accepts the sensor whether it is attached to a watch or detached, so charging does not require removing the sensor from your watch if you prefer to keep it in place.

Sleep tracking uses the included SoftBand accessory rather than the watch itself, which keeps the caseback free during the hours when sleep staging data is collected.

How the Data Reaches You

All biometric data syncs via Bluetooth to the companion app, where it is consolidated into a single view called The Reading. Rather than sending alerts, nudges, or coaching prompts, The Reading presents descriptive health insights: what your heart rate variability looked like overnight, how your movement patterns compared across the week, what your nutrition log shows alongside your recovery data.

Nutrition logging is built directly into the app, so everything appears in one place without connecting external services. Most trackers handle biometrics passively but leave nutrition to a separate third-party app. Hiyd does not.

Security and Data Handling

Hiyd uses enterprise-grade encryption. Your health data is never sold or shared. For a product category where data sensitivity is a reasonable concern, that is a straightforward commitment worth stating plainly.

One-Time Purchase, No Subscription

The sensor is a one-time hardware purchase with no monthly fee. For context, WHOOP 5.0 starts at $199 per year on subscription, and Oura Ring 4 costs $349–$499 in hardware plus $5.99 per month on top of that. Over a multi-year horizon, a one-time purchase is a structurally different cost model. For watch collectors who are already spending on their collection rather than on recurring software fees, that distinction is meaningful.

Hiyd is currently in a pilot phase ahead of its Kickstarter launch in November 2026, with the first batch shipping in Q2 2027. VIP spots are limited. You can reserve your place at hiyd.ai.

Frequently Asked Questions

Does microsuction leave any residue on the watch caseback? No. Microsuction works through physical surface contact, not adhesive chemistry. When you remove the sensor, nothing transfers to the caseback. No film, no sticky residue, no cleaning required.

Will the Hiyd sensor affect my mechanical watch movement? No. The microsuction attachment uses no magnets, so there is no magnetic field exposure during attachment, wear, or removal. The movement is not at risk of magnetisation from the sensor.

What percentage of watches does Hiyd fit? Hiyd is designed to fit 95% of mechanical watch casebacks. If it does not fit your watch, Hiyd offers a guaranteed fit or money back.

Does the sensor need to stay attached to the watch while charging? No. The charging cradle accepts the sensor whether it is attached to a watch or detached. Either works.

How does Hiyd track sleep if the sensor is on a watch? Sleep tracking uses the included SoftBand accessory rather than the watch caseback attachment. This keeps the watch free and uses a purpose-built band for overnight wear.

Is there a subscription required to use Hiyd? No. Hiyd is a one-time hardware purchase with no monthly or annual subscription fee.

When will Hiyd be available to purchase? Hiyd is launching on Kickstarter in November 2026. The first batch is scheduled to ship in Q2 2027. VIP pilot spots are currently available at hiyd.ai.