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BIBEBUVAMaster of Science in Biomedical EngineeringWireless stimulator for tactile sensationBiomedical Engineering / Thesis advisors: Prof. Dr. Volker M. Koch, Prof. Kenneth J. HuntExpert: Prof. Dr. Alejandro Hernandez ArietaProject partner: Universität Zürich, Artificial Intelligence Lab, ZürichThe sense of touch constitutes a vital feedback for a person during interaction with the environment. Thesense-actuate closed loop can be broken in the case of certain pathologies or amputation. With the aim ofreestablishing or relocating sensory feedback, this project deals with the development of two portable,dual-channel, wireless, synchronized, transcutaneous electrical stimulators(TES) with output current monitoring.The generated signal is intended to stimulate the tactile sensory receptors located on the lowerback.Daniel Lachnerdaniellachner@gmail.comProject ScopeTo study the body’s response tostimulation given different stimulationparameters, the stimulatorshown in Figure 1 is controlled bya PC via Bluetooth. A GUI hasbeen developed to modify stimulationparameters, switch modes,display output voltage, currentand skin resistance.The stimulation signal as shown inFigure 2 is square and biphasic,aiming to deliver a charge-balancedstimulus. The carrier frequency(1/[t1+t2]) can be set to avalue from 1 kHz to 10 kHz, theenvelope frequency (1/Tp) from1 Hz to 200 Hz. It is also possibleto stimulate continuously withthe carrier frequency (Tp=tb). Thestimulation amplitude can bechosen from 2.3 V to 30 V.The output current monitoringfeature allows generating similarsensations across the electrodes,independent of changes in thebody impedance.Figure 1. Developed Stimultor.As shown in Figure 3, a movingsensation can be produced, whichis a tactile illusion generated by thesynchronized stimulation of tactilereceptors by two channels withaccordingly rising and falling amplitudes.The stimulus is perceivedas a one dimensional movementbetween the two electrode pairs,which can be used as a form ofsensory feedback.Results and DiscussionThe stimulator successfully generatesthe desired signals and theGUI allows a smooth interaction.Currents are monitored on everypositive phase and displayed onthe PC where the electrode-skininterface resistance is calculated.Further tests on humans are yet tobe performed in order to characterizethe body response to thedifferent stimulus parameters.Figure 2. Stimulation SignalFigure 3. Moving Sensation.46 ti.bfh.ch