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Aerosol jet printing is a compelling technology for hybrid electronics, combining digital and noncontact patterning with broad materials compatibility, resolution as fine as ≈10 microns, and a high standoff distance of 1–5 mm. Despite its growing popularity in research environments, a robust process understanding and improved manufacturing control are essential for achieving the reliability and predictability required for broader adoption in advanced applications. Herein, recent developments in process monitoring using in‐line light scattering measurements are discussed, including their mechanistic foundations, experimental validation, relevance for process control and reliability, and value as a diagnostic tool for fundamental studies. Experimental measurements confirm the correlation between measured light scattering and deposition rate. Building on this platform, feedback from the real‐time measurement is coupled with printer software to support automated closed‐loop control via a simple proportional‐integral‐derivative software control loop. Combined with the utility of these measurements as a diagnostic to accelerate ink formulation and support fundamental process science experiments, this in‐line measurement provides a useful tool to improve print reliability with the potential to advance the adoption and capabilities of this method in conformal, flexible, and hybrid electronics applications.

 

Wearable sweat biosensors offer compelling opportunities for improved personal health monitoring and non-invasive measurements of key biomarkers. Inexpensive device fabrication methods are necessary for scalable manufacturing of portable, disposable, and flexible sweat sensors. Furthermore, real-time sweat assessment must be analyzed to validate measurement reliability at various sweating rates. Here, we demonstrate a “smart bandage” microfluidic platform for cortisol detection and continuous glucose monitoring integrated with a synthetic skin. The low-cost, laser-cut microfluidic device is composed of an adhesive-based microchannel and solution-processed electrochemical sensors fabricated from inkjet-printed graphene and silver solutions. An antibody-derived cortisol sensor achieved a limit of detection of 10 pM and included a low-voltage electrowetting valve, validating the microfluidic sensor design under typical physiological conditions. To understand effects of perspiration rate on sensor performance, a synthetic skin was developed using soft lithography to mimic human sweat pores and sweating rates. The enzymatic glucose sensor exhibited a range of 0.2 to 1.0 mM, a limit of detection of 10 μM, and reproducible response curves at flow rates of 2.0 μL min −1 and higher when integrated with the synthetic skin, validating its relevance for human health monitoring. These results demonstrate the potential of using printed microfluidic sweat sensors as a low-cost, real-time, multi-diagnostic device for human health monitoring. 

Aerosol jet printing is a popular digital additive manufacturing method for flexible and hybrid electronics, but it lacks sophisticated real‐time process control schemes that would enable more widespread adoption in manufacturing environments. Here, an optical measurement system is introduced to track the aerosol density upstream of the printhead. The measured optical extinction, combined with the aerosol flow rate, is directly related to deposition rate and accurately predicts functional materials properties such as the electrical resistance of printed graphene films. This real‐time system offers a compelling solution for process drift and batch‐to‐batch variability, rendering it a valuable tool for both real‐time control of aerosol jet printing and fundamental studies of the underlying process science.