Summary table of the reported potassium sensor devices, target fluid for which they were developed, the fluid that was used for sensor testing, the device materials, methods, performance and the stage of development.

Author (year)	Target fluid	Fluid analysed	Device materials (method)	Detection limit, concentration range, sensitivity and selectivity	Stage of development
Ghaderinezhad et al. (2020)47	Urine	Artificial urine	Crown ether on paper (colorimetry)	Calculated limit of detection of 2.39 mM	App for smartphone designed
Chitbankluai et al. (2021)48	Urine	Synthetic solutions	Crown ether modified gold nanoparticles on paper (colorimetry, visual inspection)	Testing range 0.005–1 mM	Sensor evaluated
Kucherenko et al. (2020)49	Urine	Human urine	Ion-selective membrane on graphene electrode (potentiometry)	Testing range 0.3–150 mM; sensitivity 53 mV per decade; selectivity coefficients reported	Long term storage assessed
Dębosz et al. (2021)50	Urine	Synthetic solutions and certified reference materials for urine	Ion-selective (valinomycin) octadecylamine-functionalized multi-walled carbon nanotube electrodes (potentiometry)	Testing range 0.1–100 mM; sensitivity 59.5 mV per decade; selectivity coefficients reported	3D-printed flow potentiometric measurement cell was designed
Salehan et al. (2022)51	Urine, serum	Human urine and serum	Potassium-selective aptamer DNA G-quadruplex conformation and polyaniline on a glassy carbon electrode (electrochemical impedance spectroscopy)	Limit of detection 3.7 × 10−9 mM; linear range from 10 pM to 60 μM; selectivity over other ions reported	3 urine samples and 3 serum samples were analysed
Miller et al. (2014)53	Interstitial fluid	Synthetic solutions	3D porous carbon electrodes integrated into a microfluidic channel, ISE microneedle sensor (potentiometry)	Linear range 0.1–10 mM, detection limit of 0.0022 mM; spiking with Na+ reported	Ex vivo testing
Parrilla et al. (2019)54	Interstitial fluid	Chicken and porcine skin, processed	ISE on functionalized multiwalled carbon nanotubes on a carbon-modified microneedle (potentiometry)	Limit of detection of 0.013 mM, linear response range 0.63–63 mM; selectivity coefficients reported	Ex vivo testing; in vitro cytotoxicity tested (safe for 24 hours)
Li et al. (2021)55	Interstitial fluid	Skin-mimicking phantom gel and processed chicken skin	Sodium, potassium ISFs and Ag/AgCl reference electrode in a stainless-steel hollow microneedle (potentiometry)	Testing range 0–15 mM; negligible interference from other ions	Ex vivo, measured concentrations successfully on animal skin
Wascotte et al. (2007)60	Interstitial fluid	Porcine ear skin, processed	Reverse iontophoresis for fluid extraction (flame photometry)	Testing range 0–6 mM	In vitro on porcine skin
Gao et al. (2016)64	Sweat	Human sweat	Potassium ISE multiplexed with sensors for sodium, glucose, lactate detection (potentiometry)	Testing range 1–32 mM; sensitivity 61.3 mV per decade; negligible interference from other ions	Detection during exercise demonstrated
Alizadeh et al. (2018)65	Sweat	Human sweat	Potassium ISE multiplexed with sensors for sodium detection (potentiometry)	Testing range 0.1–100 mM; sensitivity: 53.9 mV per decade; no response to Na+ ions	Detection during exercise demonstrated
Liu et al. (2019)66	Sweat	Human sweat	AlGaN/GaN high-electron-mobility transistors with potassium ion-selective membrane (electrical current)	Testing range 1 μM to 100 mM; sensitivity: 4.94 μA per decade	Detection during exercise demonstrated
Coppedè et al. (2020)67	Sweat	Potassium solutions	Textile organic electrochemical transistors modified with ion selective membrane (change in potential, electrical current)	Testing range 0.01–1000 mM; sensitivity and selectivity factor determined	Testing in various concentration solutions
Pirovano et al. (2020)68	Sweat	Human sweat	Potassium ISE multiplexed with sensors for sodium detection (potentiometry)	Testing range 0.1–316 mM; sensitivities 45.7 and 54.3 mV per decade	Detection during exercise demonstrated
Criscuolo et al. (2021)69	Sweat	Human sweat	Potassium ISE on platinum nanoflowers multiplexed with sensors for Li+, Pb2+, Na+, K+ and temperature detection (potentiometry)	Limit of detection in artificial sweat 3 mM; sensitivity in artificial sweat: 55.1 mV per decade	Detection during exercise demonstrated
Yasin et al. (2017)77	Non-invasive	Blood and ECG	Commercially available electrodes (Kardia, AliveCor) (ECG)	Blood potassium levels detected to within 9% of the blood test result	ECG data and blood samples collected from 18 patients undergoing chronic haemodialysis
Corsi et al. (2022)78	Non-invasive	Blood and ECG	12-Lead Holter H12+ Mortara Instrument Inc. (ECG)	Testing range 2.5–7.5 mM	Study population of 45 haemodialysis and 12 long QT syndrome type 2 patients
Palmieri et al. (2021)82	Non-invasive	Blood and ECG	12-Lead ECG Holter recording, H12+, Mortara Instruments (ECG)	Not reported	Study population of 29 nephrology patients
Bukhari et al. (2022)83	Non-invasive	Blood and ECG	48 h 12-lead ECGs, H12+, Mortara Instruments (ECG)	Not reported	Study population of 29 end stage renal disease patients