Ahyeon Koh

To reduce the harm of electronic waste, there is impetus to expand the use of biodegradable substrates, biocompatible materials, and battery-free devices. In this study, a piezoelectric paper composite is produced by integrating polyvinylidene fluoride-trifluoroethylene [P-(VDF-TrFE)] with the conducting polymer poly-(3,4-ethylenedioxythiophene) polystyrenesulfonate (PEDOT:PSS) and wood fiber paper. It is shown that the combined effect of PEDOT:PSS and paper leads to an enhanced out-of-plane piezoelectric coefficient in P-(VDF-TrFE), without the need for electric poling. The enhanced piezoelectric performance arises from a synergistic templating effect of PEDOT:PSS and paper that induces a sharp increase in the population of edge-on β phase P-(VDF-TrFE) crystallites. The templating effect relies on supramolecular interactions between PSS and paper that lead to PEDOT enrichment and a linear PEDOT conformation at the interface with P-(VDF-TrFE). Computational modeling reveals that linear PEDOT promotes β phase PVDF growth over the α phase due to a greater availability of hydrogen bonds. The synergistic templating of P-(VDF-TrFE) on PEDOT:PSS-coated paper opens avenues for tuning the properties of piezoelectric paper.

Mask-integrated respiratory sensors are promising for noninvasive monitoring of respiratory health outside of clinical settings, for example, to support at-home patient monitoring and telemedicine. Studies have shown the feasibility of attaching flexible and off-the-shelf sensors to face masks; however, the potential benefits of incorporating sensor materials directly onto the breathable microfibrous mesh of face masks have hardly been explored. In this work, we integrate respiratory sensors on flat polyethylene terephthalate substrates and microfibrous polypropylene face masks using an ionic liquid gel (ILG) to detect changes in local humidity during breathing. Under a DC voltage, the ILG sensors exhibit a superlinear dependence of current on humidity, resulting in enhanced sensitivity at the high humidity levels found in exhaled breath. By varying the composition of the ILG, we find an inverse relationship between the sensing signal strength and sensing kinetics, offering insights into the sensing mechanisms. Freestanding ILG films are found to be resilient under mechanical strain with humidity sensing still possible at 120% strain. Devices that are scalably integrated onto face masks produce sensors that are four times less sensitive to extreme bending at an angle of 150°. Preliminary artificial intelligence (AI) analysis of breathing patterns identifies coughs that are interspersed with regular breathing with 91% accuracy, showing the potential of AI-supported wearable masks for autonomous symptom tracking.

Hydrophilic PDMS–PEG soft wearable microfluidics are developed via one-pot soft lithography, which doubles the sweat collection volume and advances noninvasive, reliable sampling for clinical analysis.

The field of soft wearable bioelectronics requires materials that are flexible, stretchable, biocompatible, and capable of being used over long durations. Although polydimethylsiloxane (PDMS) is one of the most commonly used substrates for these devices due to its biomimetic properties compared to biological tissues, its intrinsic hydrophobicity causes it to underperform in biological environments. In this work, a hydrophilic, stretchable PDMS electrospun fibrous mat is developed to overcome this limitation by incorporating the amphiphilic polymer polyethylene glycol block copolymer (PEG‐BCP) into the porous PDMS matrix. The nonwoven hydrophilic silicone mat shows apparent improvement in stable hydrophilicity, indicated by a significant decrease in water contact angle (from 125° to 51°) for 7 days, along with improved cellular adhesion and enhanced breathability. The PDMS‐PEG fibers show higher cell proliferation than unmodified PDMS fibers, suggesting potential for long‐term biological applications. The fibrous mat also maintains its structural integrity under mechanical stress, demonstrated by a stretchability of up to 308.8% strain with reduced adhesion forces. This novel material surpasses previous PDMS fibrous substrates and enables electroless gold plating, providing a promising future for wearable fibrous electronics and biomedical devices featuring hydrophilic, stretchable, conductive, and biointegrated materials.

Paper, an inexpensive material with natural biocompatibility, non‐toxicity, and biodegradability, allows for affordable and cost‐effective substrates for unconventional advanced electronics, often called papertronics. On the other hand, polymeric elastomers have shown to be an excellent success for substrates of soft bioelectronics, providing stretchability in skin wearable technology for continuous sensing applications. Although both materials hold their unique advantageous characteristics, merging both material properties into a single electronic substrate reimagines paper‐based bioelectronics for wearable and patchable applications in biosensing, energy generation and storage, soft actuators, and more. Here, a breathable, light‐weighted, biocompatible engineered stretchable paper is reported via coaxial nonwoven microfibers for unconventional bioelectronic substrates. The stretchable papers allow intimate bioconformability without adhesive through coaxial electrospinning of a cellulose acetate polymer (sheath) and a silicone elastomer (core). The fabricated cellulose‐silicone fibers exhibit a greater percent strain than commercially available paper while retaining hydrophilicity, biocompatibility, combustibility, disposable, and other natural characteristics of paper. Moreover, the nonwoven stretchable cellulose‐silicone fibrous mat can adapt conventional printing and fabrication process for paper‐based electronics, an essential aspect of advanced bioelectronic manufacturing.

The wound healing process remains a poorly understood biological mechanism. The high morbidity and mortality rates associated with chronic wounds are a critical concern to the health care industry. Although assessments and treatment options exist, these strategies have primarily relied on static wound dressings that do not consider the dynamic physicochemical microenvironment and can often create additional complications through the frequent dressing changing procedure. Inspired by the need for engineering "smart" bandages, this study resulted in a multifaceted approach to developing an adhesive-free, permeable, and multiplex sensor system. The electronic-extracellular matrix (e-ECM) platform is capable of noninvasively monitoring chemical and physical changes in real-time on a flexible, stretchable, and permeable biointegrated platform. The multiplex sensors are constructed atop a soft, thin, and microfibrous substrate of silicone to yield a conformal, adhesive-free, convective, or diffusive wound exudate flow, and passive gas transfer for increased cellular epithelization and unobstructed physical and chemical sensor monitoring at the wound site. This platform emulates the native epidermal mechanics and physical extracellular matrix architecture for intimate bio-integration. The multiple biosensor array can continuously examine inflammatory biomarker such as lactate, glucose, pH, oxygen, and wound temperature that correlates to the wound healing status. Additionally, a heating element was incorporated to maintain the optimal thermal conditions at the wound bed. The e-ECM electrochemical biosensors were tested in vitro, within phosphate-buffered saline, and ex vivo, within wound exudate. The "smart" wound bandage combines biocompatible materials, treatments, and monitoring modalities on a microfibrous platform for complex wound dynamic control and analysis.

Electronic waste is a global issue brought about by the short lifespan of electronics. Viable methods to relieve the inundated disposal system by repurposing the enormous amount of electronic waste remain elusive. Inspired by the need for sustainable solutions, this study resulted in a multifaceted approach to upcycling compact discs. The once-ubiquitous plates can be transformed into stretchable and flexible biosensors. Our experiments and advanced prototypes show that effective, innovative biosensors can be developed at a low-cost. An affordable craft-based mechanical cutter allows pre-determined patterns to be scored on the recycled metal, an essential first step for producing stretchable, wearable electronics. The active metal harvested from the compact discs was inert, cytocompatible, and capable of vital biopotential measurements. Additional studies examined the material’s resistive emittance, temperature sensing, real-time metabolite monitoring performance, and moisture-triggered transience. This sustainable approach for upcycling electronic waste provides an advantageous research-based waste stream that does not require cutting-edge microfabrication facilities, expensive materials, and high-caliber engineering skills.

Background: The purpose of the study was to assess the effect of diet quality and physical fitness on saliva cortisol, mood, and mental distress. These relationships were compared between a peak weekday (Wednesday) and a weekend day (Saturday) when mood may fluctuate. Methods: Forty-eight healthy college students participated in the study. Participants completed the Mood and Anxiety Symptom (MASQ) and Kessler Psychological Distress Scale 10 questionnaires on Wednesday and Saturday and recorded their diet for three days. Saliva was collected before and after a workout for cortisol extraction. Results: SA had significantly higher saliva cortisol levels post-workout but lower MASQ scores on Saturday (p < 0.05). There was a very significant association between MASQ scores on Wednesday (p = 0.005), which became less significant on Saturday. In addition, lower BMI values and high-fat consumption were associated with higher cortisol levels after exercise (p < 0.05). Conclusions: There is a strong link between dietary factors, cortisol levels, mood, and time of the week. In addition, our results suggest that saliva cortisol levels may not be directly linked to negative affect but are influenced by diet quality when mental distress exists. In addition, physical fitness may play a role in improving mood during weekends.

Electronic waste (e-waste) is a global issue brought about by the short lifespan of electronics. Viable methods to relieve the inundated disposal system by repurposing the enormous amount of e-waste remain elusive. Inspired by the need for sustainable solutions, this study resulted in a multifaceted approach to upcycling compact discs (CDs). The once-ubiquitous plates can be transformed into stretchable and flexible biosensors. Our experiments and advanced prototypes show that effective, innovative biosensors can be developed at a low-cost. An affordable craft-based mechanical cutter allows pre-determined patterns to be scored on the recycled metal, an essential first step for producing stretchable, wearable electronics. The active metal harvested from the CDs was inert, cytocompatible, and capable of vital biopotential measurements. Additional studies examined the material’s resistive emittance, temperature sensing, real-time metabolite monitoring performance, and moisture-triggered transience. This sustainable approach for upcycling e-waste provides an advantageous research-based waste stream that does not require cutting-edge microfabrication facilities, expensive materials, and high-caliber engineering skills.