Tag Archives: Eun Kwang Lee

Spider web-like electronics with graphene

A spiderweb-inspired fractal design is used for hemispherical 3D photodetection to replicate the vision system of arthropods. (Sena Huh image)

This image is pretty and I’m pretty sure it’s an illustration and not a real photodetection system. Regardless, an Oct. 21, 2020 news item on Nanowerk describes the research into producing a real 3D hemispheric photodetector for biomedical imaging (Note: A link has been removed),

Purdue University innovators are taking cues from nature to develop 3D photodetectors for biomedical imaging.

The researchers used some architectural features from spider webs to develop the technology. Spider webs typically provide excellent mechanical adaptability and damage-tolerance against various mechanical loads such as storms.

“We employed the unique fractal design of a spider web for the development of deformable and reliable electronics that can seamlessly interface with any 3D curvilinear surface,” said Chi Hwan Lee, a Purdue assistant professor of biomedical engineering and mechanical engineering. “For example, we demonstrated a hemispherical, or dome-shaped, photodetector array that can detect both direction and intensity of incident light at the same time, like the vision system of arthropods such as insects and crustaceans.”

The Purdue technology uses the structural architecture of a spider web that exhibits a repeating pattern. This work is published in Advanced Materials (“Fractal Web Design of a Hemispherical Photodetector Array with Organic-Dye-Sensitized Graphene Hybrid Composites”).

An Oct. 21, 2020 Purdue University news release by Chris Adam, which originated the news item, delves further into the work,

Lee said this provides unique capabilities to distribute externally induced stress throughout the threads according to the effective ratio of spiral and radial dimensions and provides greater extensibility to better dissipate force under stretching. Lee said it also can tolerate minor cuts of the threads while maintaining overall strength and function of the entire web architecture.

“The resulting 3D optoelectronic architectures are particularly attractive for photodetection systems that require a large field of view and wide-angle antireflection, which will be useful for many biomedical and military imaging purposes,” said Muhammad Ashraful Alam, the Jai N. Gupta Professor of Electrical and Computer Engineering.

Alam said the work establishes a platform technology that can integrate a fractal web design with system-level hemispherical electronics and sensors, thereby offering several excellent mechanical adaptability and damage-tolerance against various mechanical loads.

“The assembly technique presented in this work enables deploying 2D deformable electronics in 3D architectures, which may foreshadow new opportunities to better advance the field of 3D electronic and optoelectronic devices,” Lee said.

Here’s a link to and a citation for the paper,

Fractal Web Design of a Hemispherical Photodetector Array with Organic‐Dye‐Sensitized Graphene Hybrid Composites by Eun Kwang Lee, Ratul Kumar Baruah, Jung Woo Leem, Woohyun Park, Bong Hoon Kim, Augustine Urbas, Zahyun Ku, Young L. Kim, Muhammad Ashraful Alam, Chi Hwan Lee. Advanced Materials Volume 32, Issue 46 November 19, 2020 2004456 DOI: https://doi.org/10.1002/adma.202004456 First published online: 12 October 2020

This paper is behind a paywall.

Eco-friendly nitrogen-doped graphene nanoplatelets from South Korea

South Korean researchers from Ulsan National Institute of Science and Technology (UNIST) have devised a new technique to fix nitrogen to graphene, from the July 24, 2013 news item on Azonano,

A simple, low-cost and eco-friendly method of creating nitrogen-doped graphene nanoplatelets (NGnPs), which could be used in dye-sensitized solar cells and fuel cells, is published in Scientific Reports today.

The work, carried out at Ulsan National Institute of Science and Technology (UNIST) in South Korea, could be a step towards replacing conventional platinum (Pt)-based catalysts for energy conversion.

The UNIST July 23, 2013 news release by Eunhee Song, which originated the news item, provides some context for why the technique is exciting interest,

The search for economically viable alternatives to fossil fuels has attracted attention among energy communities because of increasing energy prices and climate change. Solar cells and fuel cells are to be promising alternatives, but Pt-based (platinum-based) electrodes are expensive and susceptible to environmental damage.

Nitrogen fixation is where nitrogen (N2) in the atmosphere is converted into ammonia (NH3). Fixation processes free up nitrogen atoms from their diatomic form to be used in other ways, but nitrogen does not easily react with other chemicals to form new compounds.

The most common method of industrial nitrogen fixation is the Harber-Bosch process, which requires extremely harsh conditions, 200 atm of pressure and 400 °C of temperature.

The UNIST team previously reported that dry ball-milling can efficiently produce chemically modified graphene particles in large quantities*. This research, in Scientific Reports, presents another innovation to improve the materials. Along the way, the research team discovered a novel nitrogen fixation process.

They focus on modifications with nitrogen, developing a technique with direct nitrogen fixation, carbon-nitrogen bond formation, at the broken edges of graphite frameworks using ball-milling graphite in the presence of nitrogen gas.

In my search for this latest paper I found an earlier piece of work based on a wet-chemical reaction and published in the Journal of the American Chemical Society,

Nitrogen-Doped Graphene Nanoplatelets from Simple Solution Edge-Functionalization for n-Type Field-Effect Transistors by Dong Wook Chang, Eun Kwang Lee, Eun Yeob Park, Hojeong Yu, Hyun-Jung Choi, In-Yup Jeon, Gyung-Joo Sohn, Dongbin Shin, Noejung Park, Joon Hak Oh, Liming Dai, and Jong-Beom Baek. J. Am. Chem. Soc., 2013, 135 (24), pp 8981–8988 DOI: 10.1021/ja402555n Publication Date (Web): May 27, 2013
Copyright © 2013 American Chemical Society

That paper is behind a paywall while this latest work featuring a ‘dry’ technique is open access,

Direct nitrogen fixation at the edges of graphene nanoplatelets as efficient electrocatalysts for energy conversion by In-Yup Jeon, Hyun-Jung Choi, Myung Jong Ju, In Taek Choi, Kimin Lim, Jaejung Ko, Hwan Kyu Kim, Jae Cheon Kim, Jae-Joon Lee, Dongbin Shin, Sun-Min Jung, Jeong-Min Seo, Min-Jung Kim, Noejung Park, Liming Dai, & Jong-Beom Baek. Scientific Reports 3, Article number: 2260 doi:10.1038/srep02260 Published 23 July 2013

This team has been quite prolific recently. I last mentioned them in a June 7, 2013 posting highlighting another iteration of this ‘dry’ technique.