**4. Conclusions**

A custom software solution was designed and implemented for driving and measuring ionic elelctroactive material-based systems. The hardware setup combined separately acquired commercial off-the-shelf devices like a force sensor, a voltmeter, a linear actuation stage, and a potentiostat. To operate the electro-chemo measurement system in a synchronized manner, a new software with graphical interface was developed in LabVIEW. The IIECMS was made by combining software development kits of the implemented devices, creating algorithms for the execution of isotonic and isometric measurements, and automating the measurement and user input processes in LabVIEW. The maximum user-selectable measurement frequency for IIECMS was 160 ms. In order to operate the potentiostat in the LabVIEW, a respective set of software drivers were created with ActiveX-based SDK of the potentiostat. The IIECMS program was applied on PPy/DBS linear actuators revealing the first case of 20 dB high signal-to-noise ratio isotonic and isometric measurements with maximum force of 3 g (stress of 0.9 MPa) and strain in the range of 4.3% at oxidation. The system was easily capable of detecting mixed-mode driving and distinguishing between the cation and the anion flux induced actuation. The MWCNT-CDC fibers belonged to the second case of 0 dB low signal-to-noise ratio isotonic measurements. Partial discontinuity of the data indicated that the IIECMS setup has an occasionally appearing slack of approximately 0.7 μm, which can be eliminated with post experiment data processing. The displacement of the MWCNT-CDC fibers was found in the limitation of Δlmin

(0.5 μm) with maximum displacement at a discharging of 2 μm (0.2 % strain). The accuracy of isotonic measurement was estimated to be in the range of 0.6 μm, with the largest contributor relying on the measurement error of the position estimation resolution of LAS. Fusing the output of different channels allows for successful operation even at such challenging conditions.

Future perspectives for the IIECMS program will be to fully automate the isotonic and isometric experiments. This means that the user has an option to run both experiment types in an automated sequence, thus eliminating the need for a user to measure sample elasticity. In principle, any type of voltage- or current-driven linear actuators in the form of strips, fibers, etc., could be studied with the IIECMS program.

**Supplementary Materials:** The following are available online at http://www.mdpi.com/2073-4360/11/6/1054/s1. Figure S1 General structure of the developed software, Figure S2 Block diagram of the elasticity measurement process, Figure S3 Block diagram of potentiostat and strain measurement.

**Author Contributions:** Conceptualization, T.T.; Investigation, M.H.; Software, G.A.; Supervision, R.K.

**Acknowledgments:** The work was supported by the Estonian Research Council Grant IUT20-24.

**Conflicts of Interest:** The authors declare no conflict of interest.
