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This work presents the cyclical actuation of electric field sensitive microscale hydrogels employing dielectric coated coplanar electrodes. Microscale hydrogels are photopolymerized in-situ, and AC frequency-based actuation combined with pulse width modulation enabled controlled manipulation of hydrogel deformation. Stable actuation cycles are achieved with applied electric potentials from 20 Vpk-pk to 40 Vpk-pk, with a maximum true strain of 29% and a minimum rise time of 4.7 s. The peak and trough osmotic pressure for each system' s cycle is also analytically determined, with a peak pressure at 40 Vpk-pk of 201.1±38.3 kPa. A plateau in the peak-to-trough true strain is observed above 30 Vpk-pk. For comparative purposes a system without dielectric coated electrodes and employing external syringe pumps is also examined, and stable cyclical actuation was achieved for applied electric potentials of 5 Vpk-pk and 10 Vpk-pk. For this system the maximum stable rise time, true strain, and osmotic pressure are 8.1 s, 57%, and 429.2±81.9 kPa, respectively. The difference between the two systems highlights how optimization of the dielectric layer's thickness and uniformity can further enhance actuation performance. The electronically responsive hydrogel-based cyclical actuator developed within this work could be further employed for microfluidic regulation in portable low-power systems. [ABSTRACT FROM AUTHOR]

Biochemical sensors for continuous monitoring require dependable periodic self diagnosis with acceptable simplicity to check its functionality during operation. An in-situ self-diagnostic technique for a dissolved oxygen microsensor is proposed in an effort to devise an intelligent microsensor system with an integrated electrochemical actuation electrode. With a built-in platinum microelectrode that surrounds the microsensor, two kinds of microenvironments, called the oxygen-saturated or oxygen-depleted phases, can be created by water electrolysis, depending on the polarity. The functionality of the microsensor can be checked during these microenvironment phases. The polarographic oxygen microsensor is fabricated on a flexible polyimide substrate (Kapton) and the feasibility of the proposed concept is demonstrated in a physiological solution. The sensor responds properly during the oxygen-generating and oxygen-depleting phases. The use of these microenvironments for in-situ self-calibration is discussed to achieve functional integration, as well as structural integration, of the microsensor system. [ABSTRACT FROM PUBLISHER]