Integrated glass photonic device including dielectrophoresis selective trapping for detecting bacteria viability: An approach avoiding surface functionalization

We present an integrated glass photonic device dedicated to the sensing of bacteria viability. The targeted application is to build a water pollution sensor exploiting bacteria as sentinels. Optical integrated biosensors mostly require harmful chemical treatments of the sensing area that strongly restrain the cleanability and the regeneration of the sensor. To overcome the limitations of surface functionalization, we propose a solution where the sorting and trapping of alive and dead bacteria is based on dielectrophoretic effects provided by planar castellated electrodes integrated on a glass platform. The sensing is performed by a surface optical waveguide located in between the electrodes, whose guided light is perturbed by the particles collected at its surface. Measurements performed with 1 μm-diameter microbeads show that the device can provide a rapid discrimination of concentrations ranging from 4.55 × 107 to 2.73 × 108 particles/μl and spaced by ∼4.55 × 107 particles/μl. First tests have been carried out with alive and dead E. coli bacteria. They proved that the device is efficient at discriminating bacteria according to their viability. The optical detection of trapped bacteria has also been demonstrated for a solution of 1.5 × 106 bacteria/μl in deionized water.