Effects of COVID-19 on a CMOS fabrication course: An integrated design experience.

In the CMOS fabrication course described herein, the lecture component provides the theoretical background for semiconductor materials and integrated circuit fabrication processes. The laboratory component provides the hands-on experience required to fabricate and electrically characterize CMOS circuits in a one-semester format. A strong semiconductor device process design thread is achieved in the course by integrating the laboratory experience and process simulation/modeling and theoretical calculations. The risks associated with the COVID-19 pandemic have forced significant course modifications. The lecture is switched to a remote learning format, including pre-recorded content and weekly advanced Q&A sessions. The laboratory provides both in-person and remote sessions. Approved social distancing and cleaning protocols are practiced in the facility for in-person learning. Complementary remote learning resources are made available to all the students such as pre-recorded laboratory instructions, live video-based laboratory sessions, and web-based supplementary information. Compared to pre-pandemic semesters, the average students' GPA of the pandemic period has increased, attributed to larger and archived volumes of instructional material. Overall student comments related to course changes necessitated by the pandemic are mixed with both positive and negative feedback.

Intracellular delivery of molecules using microfabricated nanoneedle arrays.

Many bioactive molecules have intracellular targets, but have difficulty crossing the cell membrane to reach those targets. To address this difficulty, we fabricated arrays of nanoneedles to gently and simultaneously puncture 10(5) cells and thereby provide transient pathways for transport of molecules into the cells. The nanoneedles were microfabricated by etching silicon to create arrays of nanoneedles measuring 12 µm in height, tapering to a sharp tip less than 30 nm wide to facilitate puncture into cells and spaced 10 µm apart in order to have at least one nanoneedle puncture each cell in a confluent monolayer. These nanoneedles were used for intracellular delivery in two ways: puncture loading, in which nanoneedle arrays were pressed into cell monolayers, and centrifuge loading, in which cells in suspension were spun down onto nanoneedle arrays. The effects on intracellular uptake and cell viability were determined as a function of nanoneedle length and sharpness, puncture force and duration, and molecular weight of the molecule delivered. Under optimal conditions, intracellular uptake was seen in approximately 50 % of cells while maintaining high cell viability. Overall, this study provides a comparative analysis of intracellular delivery using nanoneedle arrays by two different loading methods over a range of operating parameters.

Hollow polymer microneedle array fabricated by photolithography process combined with micromolding technique.

Transdermal drug delivery through microneedles is a minimally invasive procedure causing little or no pain, and is a potentially attractive alternative to intramuscular and subdermal drug delivery methods. This paper demonstrates the fabrication of a hollow microneedle array using a polymer-based process combining UV photolithography and replica molding techniques. The key characteristic of the proposed fabrication process is to define a hollow lumen for microfluidic access via photopatterning, allowing a batch process as well as high throughput. A hollow SU-8 microneedle array, consisting of 825mum tall and 400 mum wide microneedles with 15-25 mum tip diameters and 120 mum diameter hollow lumens was designed, fabricated and characterized.

Biocompatibility of poloxamer hydrogel as an injectable intraocular lens: a pilot study.

PURPOSE: To induce irreversible gelation of poloxamer, a thermosensitive polymer hydrogel, by using a photoinitiator and ultraviolet (UV) irradiation and to verify the biocompatibility and use of poloxamer as an injectable intraocular lens (IOL) material. SETTING: Department of Ophthalmology, Seoul National University College of Medicine, Seoul Artificial Eye Center, Clinical Research Institute, Seoul National University Hospital, Seoul, Korea. METHODS: In 10 rabbits, endocapsular phacoemulsification was performed and a poloxamer-photoinitiator mixture was injected into the capsular bag through a small capsulorhexis site. In 1 eye, the capsulorhexis site was closed with a small plug and the entire eye was irradiated with UV light for 5 minutes. Postoperatively, poloxamer transparency and effect on the conjunctiva, cornea, iris, vitreous, and retina were observed. RESULTS: A mixture comprising 25% poloxamer and 0.01% photoinitiator produced a poloxamer that remained transparent in the lens capsule for up to 6 months. No inflammatory response or toxicity was observed in the conjunctiva, cornea, iris, vitreous, or retina. CONCLUSION: Poloxamer is a potentially suitable material for an injectable IOL. Further study is needed.