In this dissertation, a new iontronic device called Ionic Voltage Effect Soft Triode (IVEST) is reported and investigated. In the first part, the device was built with different construction methods. The device was constructed and characterized with intention to be based on interfacial ion adsorption and redox oxidizer depletion. The IVEST was built in a simple manner with no need for sophisticated or expensive materials. It does not utilize the control of a semiconducting channel, but an electrolyte. In different electrical circuit configurations, it can show amplification or memory effects. The device had an electrical current amplification reaching 52 
and memory effects in the electrical resistance lasting for up to 6 h. These values were achieved by tuning the electrode interface, the electrolyte and diffusion properties. In the second part, the IVEST was optimized, tuned and embedded into a memory application concept. The device is an electrochemical micro-cell, consisting of a top electrode and two bottom electrodes. The device controls the concentration and diffusion of ions by the voltage applied on the top electrode. The IVEST showed a memory effect lasting up to 6 hours. Despite the remarkably large stability time, the memory contrast was small in the first device versions. Now, we have increased the memory contrast by introducing a new external electrical circuit 
layout combined with a new operation protocol. The new investigation also reveals peculiarities of the memory and showed that the IVEST can be used in applications connected with memories. These iontronic memories show a secondary information storage connected with the read-out frequency. In the third part, the IVEST was converted to an opto-ionic device. Opto-ionic devices have not 
been extensively studied yet, and there is a need for the production of more devices capable of converting optical signals to ionic signals. The ability of the IVEST to convert the optical signal to an ionic signal is explored. Additionally, we also refer to the characterization of the opto-IVEST, which can be applied in various applications. The opto-IVEST showed the ability to detect and memorize the optical signal. Furthermore, the device exhibited synaptic learning behavior and a hybrid logic gate (AND) function.