Ceramic multilayer technology as a platform for miniaturized sensor arrays for water analysis

<p>Ion-selective electrodes (ISEs) have been proven particularly useful in water analysis. They are usually used as single-rod measuring chains in different designs, which are manufactured using precision mechanical manufacturing and assembling technologies. The paper describes a microsystem technology approach for the fabrication of miniaturized electrochemical sensors. The ceramic HTCC (high-temperature co-fired ceramic) and LTCC (low-temperature co-fired ceramic) multilayer technology enables suitable processes for the manufacturing of robust and miniaturized sensor arrays with a high functional density. Design, manufacture, and electrochemical performance of the novel ceramic multilayer-based sensor array are presented in the paper using various examples. An adapted material and process development was carried out for the sensitive functional films. Special thick-film pastes for the detection of the pH value as well as <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M1" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><msubsup><mi mathvariant="normal">NH</mi><mn mathvariant="normal">4</mn><mo>+</mo></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="24pt" height="15pt" class="svg-formula" dspmath="mathimg" md5hash="8aeb386a576ed6c8280ae774099f80e4"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="jsss-10-83-2021-ie00001.svg" width="24pt" height="15pt" src="jsss-10-83-2021-ie00001.png"/></svg:svg></span></span>, <span class="inline-formula">K⁺</span>, <span class="inline-formula">Ca²⁺</span>, and <span class="inline-formula">Cu²⁺</span> ion concentrations in aqueous solutions were developed. Ion-sensitive thick-film membranes were deposited on a ceramic multilayer sensor platform by means of screen-printing. All ISEs, integrated in the sensor array, showed suitable electrochemical performances including a very quick response (several seconds) combined with a high sensitivity (exhibiting Nernstian behaviour) in the tested measuring range. The obtained sensitivities were around 57 <span class="inline-formula">mVper decade</span>: for the pH sensor, 30 <span class="inline-formula">mVper decade</span> for calcium, 53 <span class="inline-formula">mVper decade</span> for potassium, and 57 <span class="inline-formula">mVper decade</span> for ammonium. Depending on the application, different sensitive electrodes on the ceramic sensor array can be combined as required.</p>