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

Abstract

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 silverenhancement process self-assembles a chain of micro-monopole antennas. As the size of the silver-enhanced particles grows, the chain of micro-antenna segments bridge together to complete a macro-antenna 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 radio-frequency identification (RFID) 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: (a) IgG in rabbit serum at concentration levels ranging from 20 ng to 60 ng; and (b) moisture in a sample at volumes ranging from 5µl to 40µl. 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 bio-hazardous environment, where direct electrical or optical measurement is considered to be impractical.

Self-Powered Wireless Affinity-Based Biosensor Based on Integration of Paper-Based Microfluidics and Self-Assembled RFID Antennas

“…This ensures uniformity of the gap and the procedure can be scaled across many samples. Besides, simulation results in [12] show that a smaller gap length can result in a high sensitivity of the biosensor in the situation when the gap conductance is relatively low. Even though the gap between the electrodes can be bridged by silver micromonopole antenna chain as shown in Fig.…”

“…(b) Subthreshold mode: during the silver enhancement process, the silver ions get reduced to form metallic silver. (c) Above-threshold mode: more silver ions are reduced and the path between the two electrodes are electrically bridged [12]. two electrodes that are separated by a gap where gold nanoparticles (AuNPs) conjugated antibodies are immobilized.…”

“…8. Using the procedure described in [12], anti-IgG was immobilized on the nitrocellulose surface of AuNP pad where faces the printed antenna gap. Two SE apertures with a dimension of around 1.0 mm × 1.5 mm were created on two sides of the gap on the mesoporous substrate as shown in Fig.…”

“…In this paper, we use ink-jet printing method to print the antenna with gap instead of manually creating the gap on an existing tag [12], [13]. This ensures uniformity of the gap and the procedure can be scaled across many samples.…”

“…All interrogation measurements from the biosensors (L 1 ) were normalized with respect to the measurement obtained from the calibration dipole (L 2 ). To minimize the mutual loading the sensor tag and the calibration tag were placed next to each other and a ratiometric readout technique was used [12].…”