The pH value was measured using a pH meter, type CyberScan 500 (Eutech Instruments Europe, Nijkerk, The Netherlands) and the results are shown in Figure 3.Figure 3.Transistor current behavior 17-AAG order under various pH conditions. The transistor current was measured in DC mode Inhibitors,Modulators,Libraries with the drain-source voltage at 1 V and open gate. The enclosed area in the figure depicts the linear working range of the transistors from pH 6 to …The graph shows that within the cell working range (i.e., in the pH range from 6�C8, see marked area within Inhibitors,Modulators,Libraries the figure), the pH value changes were smaller than in the range beyond pH 8 and before pH 6 while adding the same amount of acid/base. This is due to the presence of HEPES in the buffer solution.
Regarding the transistor response, we see that within the cell working range of Inhibitors,Modulators,Libraries the pH, the dependence of the transistor current with the pH is almost linear [21].The current shift between the two types of measurements can be partly attributed to the different contribution of the ionic currents and/or changes in the polymeric layer due to the prolonged measurement time. The Inhibitors,Modulators,Libraries ionic current contribution can be compensated with an analog electronic interface, which amplifies only the pH-linear dependent component of the transistor current [21].2.4. DC and AC CharacterizationTypically the characterization measurements are performed in direct current (DC) mode. So far, the transistors were first tested in aqueous media in DC mode in order to see the reaction of the polymer when DC is applied to it.
However, DC mode could be responsible for polarization effects, which in turn could Cilengitide damage the polymeric layers by degradation and/or delamination. Alternate current (AC) measuring mode could be interesting for preventing liquid-related damages and prolonging the lifetime of the devices. With the perspective of performing sensing experiments in complex media relevant for cell measurements, device characterization
Due to demand of developing low power wireless devices and systems, a growing interest in investigating event-based sampling schemes has been observed in recent years. On the system level, the representative example of event-based sampling application is a wireless sensor network that is essentially an event-based system intended to detect specified events of interest in a sensor field [1,2].
On the device level, event-based sampling has been applied in asynchronous selleck analog-to-digital converters (A-ADCs) which are a new class of converters proposed recently [3�C7]. In the A-ADCs, the periodic sampling is substituted by signal-dependent schemes where the sampling operations are triggered irregularly if a signal value varies by a specified increment. The A-ADCs are clockless circuits designed for ultra low-power and low-voltage sensing devices.The event-based schemes are attractive especially for sampling bursty signals [1,7�C9]. As known, many signals in sensory applications (e.g.