Real-time measurements of the total loss of sweat, the rate of sweating, the temperature of sweat, and the concentrations of electrolytes and metabolites in sweat can provide important insights into human physiology. Conventional methods use manual collection processes (e.g., absorbent pads) to determine sweat loss and lab-based instrumentation to analyze its chemical composition. Although such schemes can yield accurate data, they cannot be used outside of laboratories or clinics. Recently reported wearable electrochemical devices for sweat sensing bypass these limitations, but they typically involve on-board electronics, electrodes, and/or batteries for measurement, signal processing, and wireless transmission, without direct means for measuring sweat loss or capturing and storing small volumes of sweat. Alternative approaches exploit soft, skin-integrated microfluidic systems for collection and colorimetric chemical techniques for analysis. Here, we present the most advanced platforms of this type, in which optimized chemistries, microfluidic designs, and device layouts enable accurate assessments not only of total loss of sweat and sweat rate but also of quantitatively accurate values of the pH and temperature of sweat, and of the concentrations of chloride, glucose, and lactate across physiologically relevant ranges. Color calibration markings integrated into a graphics overlayer allow precise readout by digital image analysis, applicable in various lighting conditions. Field studies conducted on healthy volunteers demonstrate the full capabilities in measuring sweat loss/rate and analyzing multiple sweat biomarkers and temperature, with performance that quantitatively matches that of conventional lab-based measurement systems.

The impact of both intrinsic and plasma-induced stress of a TiN hardmask on line wiggling was investigated via etching of p-SiOCH with 28 nm pitch, line and space (L/S) EUV resist patterning. Experimental stacks included crystalline PVD TiN with an intrinsic stress of +0.1 GPa and several PEALD TiN films with varying crystallinity and intrinsic stresses ranging from -3.6 GPa (compressive) to +0.2 GPa (tensile). Results confirmed that reduction of intrinsic TiN stress can prevent wiggling1 when the mask is not exposed to plasma during process flow. However, when TiN is exposed to plasma as in a typical back end of line (BEOL) process2-3, compressive stress increased in all films and resulted in wiggling even in the patterned PVD TiN sample with low intrinsic stress. This global increase in compressive stress due to plasma exposure did not correlate with intrinsic stress values, therefore, this work suggests a greater focus should be placed on plasma-induced stress to avoid line wiggling when selecting a TiN film. Further investigation found that increased surface roughness of the TiN mask can decrease the risk of wiggling, and that surface roughness is influenced by p-SiOCH etch selectivity, indicating mask surface roughness should also be considered when evaluating line wiggling in BEOL, p-SiOCH etching.

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