This presentation focuses on the development of chipless (lacks traditional integrated circuit), passive (no power source), short wave radio frequency biosensors that can be embedded both in or on materials for wireless monitoring of biologic interactions. The flexible, spiral antennas (Fig_a) can be screen printed with conductive silver ink or patterned on copper-coated polyimide substrates and etched with a solution containing hydrogen peroxide and hydrochloric acid. The antenna’s initial resonant frequency is tuned by the coil length and spiral pitch and is targeted in the 1-100MHz range for better penetration through soil, water, and tissue. The real and imaginary components of the absorption (S11) and transmission (S21) scattering parameters are measured at a 1-10 cm distance by two loop antenna coils (Fig_b) attached to a vector network analyzer. These parameters shift when the capacitance between the antenna coils change due to variation in dielectric permittivity of the medium on top of the antenna (Fig_c). Changes in skin resistance due to charge near the copper coil also affect the scattering parameter response. We have applied this sensor platform to study the activity of hydrolytic degradation of substrate coatings (<i>e.g. </i>proteases to protein films). The wireless sensors screen effects of substrate composition and enzyme concentration on the overall degradation profile of the film via simple, multiplexed experiments. Furthermore, we show that this can be done in closed systems such as soil. We also present current efforts on transducing protein and cell interactions as well as biofilm growth using resonant sensors. This research will have broad impact in applications of measuring biologic activity where optical line of sight or direct electrical connection are inconvenient or impossible, such as monitoring the contents of a sterile, disposable bioreactor.

Short wave radio frequency resonators for transducing protein and cell surface interactions in closed systems

255th National Meeting (2018)

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