# Design and Development of OECT Logic Circuits for Electrical Stimulation Applications  
[PERSON]  
1 Tecnalia Serbla Ltd., 11000 Belgrade, Serbia; [EMAIL_ADDRESS] (S.I. ): [EMAIL_ADDRESS] (M.S.) [PERSON]  
2 Southern International Ltd., 11000 Belgrade, Serbia; [EMAIL_ADDRESS] 2  
[PERSON]  
1 Tecnalia Serbla Ltd., 11000 Belgrade, Serbia; [EMAIL_ADDRESS] (S.I. ): [EMAIL_ADDRESS] (M.S.) [PERSON]  
3 Bio and Organic Electronics Unit, Department of Smart Hardware, Digital Systems Division, RISE Research Institutes of Sweden AB, 60221 Nortkoping, Sweden; [EMAIL_ADDRESS] (P.A.E. ); [EMAIL_ADDRESS] (M.Y.M. ); [EMAIL_ADDRESS] (S.J. ); [EMAIL_ADDRESS] (L.H.) TECnALIA, Basque Research and Technology Alliance (BRTA), 2009 San Sebastian, Spain; [EMAIL_ADDRESS] 2  
[PERSON]  
3 Bio and Organic Electronics Unit, Department of Smart Hardware, Digital Systems Division, RISE Research Institutes of Sweden AB, 60221 Nortkoping, Sweden; [EMAIL_ADDRESS] (P.A.E. ); [EMAIL_ADDRESS] (M.Y.M. ); [EMAIL_ADDRESS] (S.J. ); [EMAIL_ADDRESS] (L.H.) TECnALIA, Basque Research and Technology Alliance (BRTA), 2009 San Sebastian, Spain; [EMAIL_ADDRESS] 2  
[PERSON]  
3 Bio and Organic Electronics Unit, Department of Smart Hardware, Digital Systems Division, RISE Research Institutes of Sweden AB, 60221 Nortkoping, Sweden; [EMAIL_ADDRESS] (P.A.E. ); [EMAIL_ADDRESS] (M.Y.M. ); [EMAIL_ADDRESS] (S.J. ); [EMAIL_ADDRESS] (L.H.) [PERSON]  
4 TECnALIA, Basque Research and Technology Alliance (BRTA), 2009 San Sebastian, Spain; [EMAIL_ADDRESS] 4  
[PERSON]  
1 Tecnalia Serbla Ltd., 11000 Belgrade, Serbia; [EMAIL_ADDRESS] (S.I. ): [EMAIL_ADDRESS] (M.S.) Footnote 12: email:  
placement site of the biomedical electrodes. The challenge is that the optimal electrode configuration is dependent on multivariable factors such as the electrode-skin interface, the skin impedance, and the physical characteristics of the underlying structures. Thus, it is person-specific and can change daily for each person, requiring long set-up times or even expert knowledge for effective application [17]. Multi-pad electrodes have been proven to be an effective approach to achieve dynamic changes of the shape, size and configuration of the electrodes and as such have been used to address naturally occurring variability in biological systems [1]. They comprise a matrix of independent pads that can be grouped into subsets, named virtual electrodes, where the pads can be activated in a sequence or simultaneously. By allowing a programmable interface to alter the active electrode surface and position, multi-pad electrodes provide a solution for control of current propagation personalized to each user [18]. The size and resolution of the virtual electrodes that can be produced is primarily determined by the number of pads in the electrode. However, this number is limited in the state-of-the-art systems. As both the stimulation source and the switching logic are all in the external device (the stimulator), each pad needs an output channel on the stimulation device and an input lead to the electrode. As the number of pads grows, so does the complexity of such systems, making them increasingly cumbersome for production and use and imposing a hard practical limit on the manageable number of pads. To address this issue and facilitate a drastic increase in the number of pads, we propose a method for migration of the active electronic components responsible for pad selection and configuration into the multi-pad electrode by leveraging the technology of screen-printed organic electrochemical transistors (OECTs). It has previously been demonstrated that screen-printed OECT-based circuits can be used to reduce the input/output (I/O) number on the external addressing electronic circuits [19]. This can be achieved by screen-printing various kinds of logic circuits that interpret the input signals provided by the external electronics.