Stability of the microdroplets for portable biosensor.

This paper highlights the behavior of microdroplets used for portable biosensors. Microdroplets have been applied for various Lab-on-a-chip applications, in which portability/wearable is becoming a trend word. However, the resonance (sloshing phenomena) of the microdroplets could be an issue. For example, bilayer lipid membrane, fragile characteristics due to its thickness of 5 nm, easily ruptures by jiggling. We therefore prepared various dimensions of droplets by changing the well shape, and examined the resulting waves depending on the vibration frequency between 20 and 100 Hz, including daily life frequencies. Moreover, we investigated an influence of surface coating of the wells by the same tests. The results of the first examination showed that the sloshing was effectively suppressed by reducing the well length along the vibration axis. We also found that the sloshing was suppressed by reducing surface energy of the microwells. We succeeded in clarifying the characteristics of microdroplets at the vibration in daily life frequency, which will be useful information for development of portable biosensors.