Wireless Biosensing Using Silver-Enhancement Based Self-Assembled Antennas in Passive Radio Frequency Identification (RFID) Tags

In this paper, we present a silver-enhancement technique for self-assembling radio frequency (RF) antennas and demonstrate its application for remote biosensing. When target analytes or pathogens are present in a sample the silver-enhancement process self-assembles a chain of micromonopole antennas. As the size of the silver-enhanced particles grows, the chain of microantenna segments bridge together to complete a macroantenna structure. The change in the electrical impedance across the bridge modulates the reflection properties of the antenna at a desired frequency. In this paper, we have used this principle to model, optimize and design a ratiometric mode 915-MHz RF identification-based biosensor which uses relative received signal strength indicator (RSSI) to measure and detect different concentration levels of target analytes. We have validated the proof-of-concept for detecting two types of analytes: 1) IgG in rabbit serum at concentration levels ranging from 20 to 60 ng and 2) moisture in a sample at volumes ranging from 5 to 40 μL. A significant advantage of the proposed biosensor is that the concentration level of target analytes or pathogens can be remotely interrogated in a concealed, packaged or in a biohazardous environment, where direct electrical or optical measurement is considered to be impractical.