A Protocol to Characterize pH Sensing Materials and Systems

Abstract

Although significant progress is made in identifying pH sensing materials and device configurations, a standard protocol for benchmarking performance of next-generation pH devices is still lacking. In particular, key properties of characterization systems, such as inherent component contributions, time plots for extended-gate field-effect transistor (EGFET) measurements, and the input resistance (R in ), often go unreported in studies of pH sensing systems. These properties strongly influence the characterization system and can lead to mistaken attribution of properties to the device. In this paper, a series of essential characterization tests and parameters are reported to evaluate pH systems, such as the zinc oxide EGFET, in a standardized protocol. This EGFET ZnO sensor has a sensitivity of −58.1 mV pH −1 , drift range from 2.5 to 14.2 µA h −1 , and response time of 136 s. By using a ZnO sensing electrode, it is demonstrated that i) intrinsic contributions of reference electrode and commercial transistor (for EGFET) are not negligible; ii) time plots for EGFET configuration and defining a critical point at the onset of drift are essential for accurate sensitivity, response time, and drift reporting; and iii) the results of the pH sensing system are strongly dependent on the input resistance of the used characterization instruments. pH Sensor Benchmarking

Recent Progress in Electrochemical pH-Sensing Materials and Configurations for Biomedical Applications

“…Whether the RE is solution filled, usually with potassium chloride (KCl), or gel filled, usually with sodium chloride (NaCl), can have an effect on the stabilization time with a response time in the range of tens of seconds or tens of minutes, respectively. 132 Common problems that REs may exhibit are that some electrodes may (i) suffer from leakage of inner electrolytes, (ii) get contaminated, 105 and (iii) require frequent calibration, as some electrodes are less stable, especially ones that are microfabricated. 132 In addition, the inherent properties and behaviors of sensing materials such as thickness, crystallinity, and composition must be considered.…”

Acrylamide Hydrogel-Modified Silicon Nanowire Field-Effect Transistors for pH Sensing

“…Meanwhile, Figure 7c,d shows the regularly and repeatedly electrical signal response of the hydrogel-modified SiNW FET in different buffer pH solutions, and the current rate of change ranges from 58 to 12,339 with an excellent exponential correlation (R 2 > 0.99). Table 1 lists a pH sensitivity comparison of the relevant reported FET sensors [13,19,[35][36][37]. The results show that the hydrogel-functionalized SiNW FET sensors have a satisfactory performance to pH sensors prepared by other methods and can be applied in future pH sensing instant applications.…”

Ubiquitous conformable systems for imperceptible computing

“…Although great progress has been achieved, many studies have failed to report key parameters for reproducibility and accurate benchmarking of materials and fabrication steps. To this end, widely accepted conventions for determining materials, processes and manufacturing steps would be helpful to compose global protocols (Obidin et al, 2019;Ghoneim, 2019b). Widespread use of such protocols would help to sustain continuous advancement in the field of conformable devices and enable rapid progress in commercialization.…”