Benchtop Performance of Novel Mixed Ionic-Electronic Conductive Electrode Form Factors for Biopotential Recordings.

Background: Traditional gel-based (wet) electrodes for biopotential recordings have several shortcomings that limit their practicality for real-world measurements. Dry electrodes may improve usability, but they often suffer from reduced signal quality. We sought to evaluate the biopotential recording properties of a novel mixed ionic-electronic conductive (MIEC) material for improved performance. Methods: We fabricated four MIEC electrode form factors and compared their signal recording properties to two control electrodes, which are electrodes commonly used for biopotential recordings (Ag-AgCl and stainless steel). We used an agar synthetic skin to characterize the impedance of each electrode form factor. An electrical phantom setup allowed us to compare the recording quality of simulated biopotentials with ground-truth sources. Results: All MIEC electrode form factors yielded impedances in a similar range to the control electrodes (all <80 kΩ at 100 Hz). Three of the four MIEC samples produced similar signal-to-noise ratios and interfacial charge transfers as the control electrodes. Conclusions: The MIEC electrodes demonstrated similar and, in some cases, better signal recording characteristics than current state-of-the-art electrodes. MIEC electrodes can also be fabricated into a myriad of form factors, underscoring the great potential this novel material has across a wide range of biopotential recording applications.

Synthesis of ultrathin zeolite Y membranes and their application for separation of carbon dioxide and nitrogen gases.

Synthesis of zeolite Y membranes from submicrometer (>100 nm) and nano seed (<100 nm) crystals on alumina supports was examined and the separation characteristics of these membranes for CO(2) and N(2) were studied. Two secondary growth solutions were examined, one for a rapid growth (hours) and one for a slower growth process (days). Membranes formed from the rapid growth solution resulted in 2-2.5 microm thickness, while for the slower growth solution, a dense membrane of 350-600 nm thickness was formed, covered by a 25 microm porous zeolite layer. With the nano seeds as the seeding layer, no membrane was formed. A mechanism involving seed dissolution to initiate membrane formation is concluded. The separation characteristics of membranes for CO(2)/N(2) separation were similar, with very high selectivities for separation (alpha(CO(2),N(2)) > 500). The thicker membrane had lower permeance. By investigating both single gas and mixed gas permeances, strong evidence for a percolative type separation process is obtained.