E-Tattoos: Toward Functional but Imperceptible Interfacing with Human Skin.

The human body continuously emits physiological and psychological information from head to toe. Wearable electronics capable of noninvasively and accurately digitizing this information without compromising user comfort or mobility have the potential to revolutionize telemedicine, mobile health, and both human-machine or human-metaverse interactions. However, state-of-the-art wearable electronics face limitations regarding wearability and functionality due to the mechanical incompatibility between conventional rigid, planar electronics and soft, curvy human skin surfaces. E-Tattoos, a unique type of wearable electronics, are defined by their ultrathin and skin-soft characteristics, which enable noninvasive and comfortable lamination on human skin surfaces without causing obstruction or even mechanical perception. This review article offers an exhaustive exploration of e-tattoos, accounting for their materials, structures, manufacturing processes, properties, functionalities, applications, and remaining challenges. We begin by summarizing the properties of human skin and their effects on signal transmission across the e-tattoo-skin interface. Following this is a discussion of the materials, structural designs, manufacturing, and skin attachment processes of e-tattoos. We classify e-tattoo functionalities into electrical, mechanical, optical, thermal, and chemical sensing, as well as wound healing and other treatments. After discussing energy harvesting and storage capabilities, we outline strategies for the system integration of wireless e-tattoos. In the end, we offer personal perspectives on the remaining challenges and future opportunities in the field.

Ocular surface disorder in pterygium: role of conjunctival impression cytology.

OBJECTIVE: To study ocular surface abnormalities in patients with pterygium, conjunctival impression cytology was explored as a tool for the assessment of the cytological changes. MATERIALS AND METHODS: A comparative case control study was undertaken to evaluate the ocular surface disorders in pterygium. Fifty cases of pterygium and 50 age and sex-matched controls were analyzed for the presence of local tear film abnormalities as assessed by the tear film break up time and Schirmer test. The spectrum of changes in cytomorphology was studied in detail using conjunctival imprint cytology. RESULTS: Tear film break-up time and Schirmer's strip wetting were found to be significantly different in study and control groups. Studying the cytomorphology of the conjunctival imprint smears, reduced cellularity and squamous metaplasia of different grades was observed more frequently in patients compared to controls. On overall grading of cytological changes, statistically significant difference was noted between the study and control groups (P value 0.00172). CONCLUSION: From the present study we can suggest that aqueous tear film deficiency leading to ocular surface disorder brings about a change at the cytological level, and ocular surface disorders found in pterygium can be interpreted by conjunctival impression cytology.