Figure 1.

Advances in wearable biosensors. As continuous biosensors have advanced, continued innovation has enabled smaller and more biocompatible designs. (A) Percutaneous biosensors are an established technology that makes up the bulk of wearable biosensors on the market. They can be applied simply by patients and can carry biosensor signals across the skin through a physical connection. However, the device’s lifetime is limited by chronic inflammation and skin turnover. (B) Implantable biosensors were created to address these limitations. They package an optical sensor with an optoelectronic reader, an external transmitter for power and communication, and an anti-inflammatory steroid depot, all housed within a polymer capsule. These biosensors transmit signals wirelessly across the skin to circumvent the limited device lifetimes of the percutaneous biosensors. However, they are large enough to require outpatient surgery to implant and remove. C. In our insertable biosensors, optoelectronics are located in the wearable device, while the implant contains only the stabilized phosphors within a carrier hydrogel. This allows the biosensors to be much smaller and simpler to inject and simpler to manufacture. Because they can be created using a wide range of hydrogels, our insertable biosensors can be made with customizable biodegradability and minimal inflammatory response.