Chang Young Lee

Wearable contact lenses which can monitor physiological parameters have attracted substantial interests due to the capability of direct detection of biomarkers contained in body fluids. However, previously reported contact lens sensors can only monitor a single analyte at a time. Furthermore, such ocular contact lenses generally obstruct the field of vision of the subject. Here, we developed a multifunctional contact lens sensor that alleviates some of these limitations since it was developed on

Biological ion channels are able to generate coherent and oscillatory signals from intrinsically noisy and stochastic components for ultrasensitive discrimination with the use of stochastic resonance, a concept not yet demonstrated in human-made analogs. We show that a single-walled carbon nanotube demonstrates oscillations in electroosmotic current through its interior at specific ranges of electric field that are the signatures of coherence resonance. Stochastic pore blocking is observed when

The formation of three-dimensional (3D) interconnections is essential in integrated circuit packaging technology. However, conventional interconnection methods, including the wire-bonding process, were developed for rigid structures of electronic devices, and they are not applicable to the integration of soft and stretchable electronic devices. Hence, there is a strong demand for 3D interconnection technology that is applicable to soft, stretchable electronic devices. Herein, we introduce the ma

Graphene as an atom-thick carbon material is promising for the detection of gaseous molecules owing to extremely high surface-to-volume ratio. However, the majority of graphene-based gas sensors, prepared by chemical vapor deposition (CVD), have suffered from non-uniformity in their responses. Such a high sensor-to-sensor variation in responses has not been systematically studied, limiting application of graphene gas sensors. Here we report processes that lead to a highly sensitive and uniform g

Adsorption dynamics and their influence on signal transduction for carbon nanotube-based chemical sensors are explored using continuum site balance equations and a mass action model. These sensors are shown to possess both reversible and irreversible binding sites that can be modeled independently. For the case of irreversible adsorption, it is shown that the characteristic response time scales inversely with analyte concentration. It is inappropriate to report a detection limit for this type of

This paper explores the possibility of using arrays of metallic carbon nanotubes as sensors. Unlike their semiconducting counterparts, single-walled carbon nanotube arrays or networks that are dominated by metallic conduction pathways have not been investigated for their environmental sensitivity. In this work, we demonstrate transduction of molecular adsorption via charge transfer through predominantly metallic single-walled carbon nanotubes. Raman spectroscopy and electric field dependent tran

Sensing in reverse: Reversible detection of as few as 109 molecules (1700 aM) of dimethyl methylphosphonate, a nerve agent simulant, is demonstrated at the end of a micro GC column (see picture). Such arrays form the basis of rapidly transducing molecular sensors with micrometer-sized footprints. The separation capability of the column eliminates the need for selectivity on the sensor, as long as analyte binding is reversible and rapid.

Coronavirus has affected the entire global community owing to its transmission through respiratory droplets. This has led to the mandatory usage of surgical masks for protection against this lethal virus in many countries. However, the currently available disposable surgical masks have limitations in terms of their hydrophobicity and reusability. Here, we report a single-step spray-coating technique for the formation of a superhydrophobic layer of single-walled carbon nanotubes (SWCNTs) on a mel

A wide range of analytes adsorb irreversibly to the surfaces of single walled carbon nanotube electronic networks typically used as sensors or thin-film transistors, although to date, the mechanism is not understood. Using thionyl chloride as a model electron-withdrawing adsorbate, we show that reversible adsorption sites can be created on the nanotube array via noncovalent functionalization with amine-terminated molecules of pKa < 8.8. A nanotube network comprising single, largely unbundled nan

-substituted triphenylene, as well as the hole-doping effect caused by triphenylene, which increases the binding affinity to the electron-donating DMMP. The proposed approach for simple functionalization of graphene with substituted triphenylene can potentially be employed in tuning the properties of other conjugated nanomaterials, such as carbon nanotubes and graphene nanoribbons, to detect various target analytes.

The extreme evaporative loss of water from topsoil complicates cultivation in arid areas, and artificial plastic mulches that imitate sand mulches may minimize such water losses. However, the application of such plastic mulches is limited by their high cost and non-biodegradability. In this study, we developed superhydrophobic sand grains to reduce evaporative water loss from soil. Sea sand (SS) was coated with silica sol, which was prepared by the hydrolysis of tetraethoxysilane (TEOS) under al

-cresol, 2-chlorophenol, respectively. We attribute the high adsorption capacity of our platform to efficient adsorbate-CNT interaction within the narrow interstitial channels between the aligned nanotubes. The CNT-based adsorption tubes are highly promising for the simple and efficient removal of phenolic and other types of organic pollutants.

The SDS transection approach is simple and inexpensive, yet provides flexibility in studying neuroregeneration, particularly when it is important to make sure there are no retrograde signals from the distal segments affecting regeneration. Neurons are known to not only be under tension but also balanced in terms of force, and the balance is obviously disrupted by transection. Our experimental platform, verified with Aplysia, can be extended to mammalian systems, and help us gain insight into the

Superhydrophobic coatings have broad applications across various fields but often face challenges, such as complexity, high cost, low mechanical/thermal stability, toxicity, and environmental hazards. In this study, we demonstrate a simple, scalable, eco-friendly, and durable spray-coating method using bioadhesive shellac and octadecyltrichlorosilane (OTS)-modified silica nanoparticles to create superhydrophobic surfaces. The silica nanoparticles impart superhydrophobicity by forming hierarchica

The integration of microfluidic devices-which efficiently handle small liquid volumes-with separations/mass spectrometry (MS) is an effective approach for profiling the neurochemistry occurring in selected neurons. Interfacing the microfluidic cell culture to the mass spectrometer is challenging because of geometric and scaling issues. Here we demonstrate the hyphenation of a neuron-in-capillary platform to a solid phase extraction device and off-line MS. A primary neuronal culture of Aplysia ca