br Design methods and materials br

Design, methods and materials
Results
Discussion and conclusion We proposed and demonstrated a biosensing platform utilizing circular current lines fabricated on the sensing area and fluorescent magnetic nanoparticles as labels. The current line design provides excellent control over the motion of magnetic beads over a small area. The circular shape of the current lines enabled the manipulation of about three times as many magnetic beads as linear current lines. The fluorescence property of the FG beads enabled rapid detection using a readily available microscope that buy R406 is not affected by electrical noise generated by magnetic fields used to manipulate magnetic particles. Our current line design was used to detect FG beads that were bonded by streptavidin-biotin interaction, where approximately 1.4×104 streptavidin-biotin bonds were detected within 4min. This is fast compared to conventional antibody-antigen based detection methods, such as enzyme linked immunosorbent assay (ELISA) that take several hours. Notably, optical detection opens up the possibility of integrating our method with smartphones for imaging the sensing region and processing the results. In our future work, we will explore these ideas to create a rapid and sensitive smartphone based system for medical diagnostics.
Acknowledgement This research is partially supported by the Medical Research and Development Programs Focused on Technology Transfer: Adaptable and Seamless Technology Transfer Program through Target-Driven Research and Development (A-STEP) from Japan Agency for Medical Research and development, AMED through Grant No. 15im0302513h0102.
Introduction Many industries employ electric field measurement for various applications such as power system monitoring [1–5], electrostatic detection [6–8], and atmospheric science [9–11]. DC electric field measurement is known to be comparatively more complicated than ac field measurement due to the lack of cyclic variation with respect to time. Field mill devices are often employed for dc field measurement. These devices convert the dc field into an alternating field by employing an electrically grounded shutter to periodically shield sense electrodes from the incident dc field. A few micromachined electric field mill (MEFM) designs have been investigated and fabricated based on the concept of the macroscopic field mill [12–17]. Most of the designs apply a vibrating perforated grounded shutter to periodically shield underlying sense electrodes from the incident dc field (see Fig. 1). As interference from the drive voltage can limit resolution, low voltage drives are more preferable for increased sensitivity. In some cases, resonant motion of shutter is used to further reduce the driving voltage. This was demonstrated by Wijeweera et al. [17], where a resonant shutter driven by low voltage thermal actuators was implemented. The sensor demonstrated a minimum detectable field strength at 42V/m, which outperformed most of the other MEFM reported [12–16]. While performance was excellent, the sensor\'s structural parameters were not fully optimized, limiting is potential sensitivity. A study on MEFM design optimization was undertaken by Gong et al. [18] for two different designs of MEFM, perpendicular-vibration MEFM and parallel-vibration MEFM. The structure parameters, including width of perforations (slits in the shutter), shutter thickness, and gap between the shutter and underlying electrodes, were optimized to achieve a maximum amount of induced charge on the exposed electrodes. These studies were based on the assumption that there would be no induced charge on the electrodes when visibly shielded by the shutter. However, this is not the case, as shielded electrodes are charged by the incident field due to fringing under the shutter. Therefore, a study of the operational performance of an MEFM must consider the differential charge between visibly shielded and exposed electrodes under the vibrating shutter.