Bioresorbable Wireless Sensors as Temporary Implants for In Vivo Measurements of Pressure

Pressures at targeted locations inside the human body serve as critically important diagnostic parameters for monitoring various types of serious or even potentially fatal medical conditions including intracranial, intra-abdominal, and pulmonary hypertension, as well as compartment syndromes. Implantable commercial sensors provide satisfactory accuracy and stability in measurements of pressure, yet surgical removal is required after recovery of the patient to avoid infections and other risks associated with long-term implantation. Sensors that dissolve in biofluids (or, equivalently, bioabsorb or bioresorb) avoid the need for such surgeries, yet current designs involve either hard-wired connections and/or fail to provide quantitative measurements over clinically relevant lifetimes. Here, a bioresorbable, wireless pressure sensor based on passive inductor-capacitor resonance circuits in layouts and with sets of materials that overcome these drawbacks is reported. Specifically, optimized designs offer sensitivity as high as ≈200 kHz mmHg⁻¹ and resolution as low as 1 mmHg. Encapsulation approaches that use membranes of Si₃N₄ and edge seals of natural wax support stable operation in vivo for up to 4 days. The bioresorbable pressure sensing technology reported here may serve as an important solution to temporary, real-time monitoring of internal pressure for various medical conditions.