Smart contact lenses, electronic tattoos and implants: what exists today
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Image description: Conceptual illustration of an eye, an open hand and a heart-shaped glow joined by dotted patterns.
A watch or ring sits on your body. Other sensor designs move closer: a lens on the eye, thin electronics against the skin, or a monitor inserted beneath it. Some already have specific clinical uses. Others remain experiments with limited testing.
The location alone tells you very little about what a sensor can do. A contact lens that detects changes in eye shape is different from one being studied for tear glucose. A skin patch that samples sweat is different from a glucose sensor inserted under the skin. Their power supplies, evidence and maintenance differ, too.
Here is where those approaches stand, including the equipment that remains outside the body and the questions worth asking about a new claim.
Smart contact lenses: eye signals and tear glucose
A sensor lens needs more than a small sensing element. Its electronics must collect a usable signal and communicate it, while the lens remains suitable for the eye. Researchers investigate wireless power and data transmission because a bulky battery or cable would limit how a lens could be worn.
There is already a specific clinical example. In 2016, the FDA permitted marketing of Sensimed Triggerfish. Its single-use lens detects small changes in eye volume during wear of up to 24 hours. An antenna around the eye and a portable recorder collect information that can help a clinician choose when to measure eye pressure.
That purpose matters. Triggerfish does not directly measure intraocular pressure, diagnose glaucoma or correct vision. Its signal is not the pressure reading obtained during an eye examination. It is used under professional supervision, with its own fitting requirements and possible eye irritation.
Glucose-sensing lenses address a separate problem. A 2024 contact-lens study investigated the relationship between tear glucose and blood glucose in 20 participants, half with diabetes. The researchers used individual calibration and accounted for differences in timing between the two fluids during controlled drink-challenge sessions.
That is evidence about a particular prototype and method. It does not establish a contact lens that can replace a prescribed glucose monitor during ordinary daily use. Detecting glucose in tears, estimating a blood-glucose value and making a safe treatment decision are separate steps that each need evidence.
Electronic tattoos: thin interfaces, different measurements
An electronic tattoo usually means a very thin electronic interface attached to skin. It need not be a permanent decorative tattoo, and it need not contain the complete recording system. Different research designs target cardiac activity, blood pressure, temperature, sweat chemistry, hydration-related signals or ultraviolet exposure.
One example is a 2022 graphene bioimpedance study. Researchers combined thin graphene interfaces with measurements and a model to estimate blood pressure, reporting recordings longer than 300 minutes. The study reporting summary identifies seven presumed-healthy participants aged 18–35. Repeated readings from that small group do not establish performance across older adults or people with hypertension.
Other designs measure something outside the body. Heo and colleagues' 2018 research tested small wireless, battery-free light dosimeters, including devices worn on skin or fingernails during outdoor activities. A UV sensor records exposure at its location. It does not block sunlight or demonstrate that every wearer will avoid skin cancer.
Thin, flexible contact can help a sensor follow the body, but adhesion, sweat, movement and skin tolerance still matter. A successful prototype does not prove that one tattoo can measure all these signals, stay accurate indefinitely or operate without supporting electronics. For clinical blood-pressure monitoring, the FDA's warning about unauthorized devices is a reason to check the actual device and intended use.
Implantable monitors: established uses and ongoing support
Insertable cardiac monitors record heart-rhythm information beneath the skin over an extended period. Medtronic's LINQ II documentation describes subcutaneous ECG recording for specified clinical circumstances. This is prescribed monitoring, with a clinician deciding whether it fits the patient's needs.
Insertion has risks, and an implant does not remove the need to manage communication equipment or follow-up. Recording an event also does not mean a clinician sees or responds to it immediately.
Device-specific safety information belongs in that discussion. On October 19, 2026, the FDA's reset-related LINQ II recall record remained open. It describes a problem that can interrupt detection and reporting of certain events, with subsequent updates recorded. A separate moisture-ingress recall, involving eight specified devices, was terminated in May 2026. Those records have different scopes; neither supports guessing whether an individual person's monitor is affected. That requires its device details and the clinical team's advice.
Implantable glucose monitoring is also established. The FDA's Eversense 365 review describes a prescription system with an inserted sensor, an external smart transmitter and a mobile app. The sensor measures glucose in interstitial fluid and receives power from the transmitter. The system includes equipment worn outside the body, along with insertion, removal and calibration requirements.
These examples show why “implantable” is a description of placement, not a promise of a complete invisible system. They also do not establish a general-purpose implant for every hormone, temperature change or blood-chemistry measurement. Each proposed use needs its own evidence.
Jewelry and clothing: sensors in familiar objects
Health-sensing jewelry and garments offer other ways to maintain contact with the body. The electronics may look less conspicuous, but the sensor and its intended use still determine what the result means.
Oura's ring documentation provides an example of optical sensing, temperature sensing and motion sensing in jewelry. That linked page describes Ring 4 specifically. Its listed features should not be assumed to apply to every Oura generation or to mean that a ring directly measures blood glucose.
Hexoskin's sensor-placement guidance describes garment-based ECG, breathing and movement measurements with a recording system. Sensoria's textile-sensor description explains how sensors in socks connect to detachable electronics and an app for information such as foot loading and cadence.
These are examples of different measurement arrangements, not interchangeable medical devices. Fit, contact, recording equipment, compatible software and care instructions can all affect whether a garment produces useful information. A manufacturer describing running measurements does not establish that a sock prevents injuries or that a shirt diagnoses disease.
Patches: glucose and sweat are different samples
A patch is another form factor, rather than one particular measurement. Some systems place a sensor filament beneath the skin. Others collect sweat from its surface.
The FDA's Stelo clearance announcement describes an over-the-counter glucose sensor and app for adults who do not use insulin. It is not intended for people with problematic hypoglycemia. That scope should stay attached to any explanation of the device; over-the-counter access does not make it suitable for everyone.
Nix's system description takes a different approach: a rechargeable reusable pod attaches to a single-use sweat patch and communicates with an app. Its FAQ explains that local sweat readings are used to estimate a whole-body sweat profile. The device needs sufficient sweating, correct placement and an appropriate patch.
A sweat estimate is not a direct measurement of blood electrolytes or a complete assay of hydration throughout the body. Likewise, an adhesive patch is not necessarily a self-contained, battery-free sensor. Ask which component collects the sample, which processes the signal and which sends the result.
Small sensors still need energy
Researchers explore energy from body heat, movement and light, as well as wireless power supplied by another device. Different designs have different budgets for sensing, calculation and communication.
A 2024 thermoelectric-generator study describes a prototype intended to support electronics operating at microwatt scales. Its output depends on the thermal conditions and activity. It is not evidence that a complete smartwatch can run indefinitely on body heat.
The supporting equipment can be easy to miss in a demonstration. Triggerfish uses a separate recorder. The Eversense sensor receives power from an external transmitter. The Nix pod needs recharging. A battery-free sensing element may still depend on a nearby reader, a phone or other powered equipment.
For something worn on skin, ask about charging, replacement and skin care. For an inserted device, ask the clinical team how it is checked, maintained and eventually removed or replaced. Smaller hardware does not make those responsibilities disappear.
More data needs a clinical purpose and a privacy plan
Frequent measurements could help investigate symptoms or follow a known condition, but detecting more events is not itself proof of better health. In the LOOP randomized trial, implantable monitoring increased atrial-fibrillation detection in a screening population without a statistically significant reduction in the primary stroke or systemic-embolism outcome. That finding concerns that screening strategy; it does not settle the value of monitoring for every patient with symptoms.
The data pathway also deserves attention. A sensor may send records through a phone, a manufacturer's service and a clinical platform. Check who can access the records, what is shared, how long it is retained, whether you can export or delete it, and what happens when a service ends.
Health information in a consumer app is not automatically protected by HIPAA. HHS explains that the app provider's relationship to the regulated health-care system matters. Other rules may apply; the FTC's health-app guidance describes that distinction. A privacy policy is a place to examine the answers, not proof that every use is acceptable to you.
Reading the next announcement
Clinical products, early experiments and proposed designs can appear beside one another in an emerging-technology story. Look for the exact measurement and the evidence behind it. Was the system tested in people, how many participated, and under what conditions? Does its authorization cover the advertised use? What equipment and maintenance did the demonstration require?
For the underlying measurements, our wearable sensor guide explains the difference between a collected signal and an estimate. Those questions apply whether the sensor sits in a watch, on the eye or beneath the skin. A prototype can be worth studying without a guessed date for when it will become an everyday health tool.