November 15, 2019 by admin 0 Comments

Development of an effective sample transfer device for biomarker detection in nasal secretions

Authors
Young Ju Lee (a), Jae-Chul Lee (b), Young Gyu Eun (c), Gi-Ja Lee (a)
Abstract
Nasal secretions (NS) reflect inflammatory activity of the nasal mucosa and thus can be utilized for disease diagnosis and determining treatment effects in Allergic rhinitis (AR). However, non-standardized collection of samples can affect the measured concentration of inflammatory biomarker in NS. In this study, we aimed to develop and evaluate new devices capable of standardizing the collection, storage, and preprocessing methods of NS samples. First, we chose the best swab as polyester (PE) and selected a stimulation method, twirling for 10 s at 1 Hz, to efficiently release AR biomarkers from a PE swab. Storage of sample solutions at −20 °C was optimal for the stability of biomarkers for the detection of AR. The new swab sample transfer device showed excellent concentration recovery efficiency (90–100%) for tryptase (Trp) and eosinophil cationic protein (ECP) without crosstalk between the two biomarkers. Finally, we compared the concentration of Trp in human NS samples of AR patients (n = 6) pre-processed by the new device with that by centrifuge as a standard method. As a result, the concentrations of Trp in NS were very similar in both groups. Therefore, this device can be utilized as an effective sample transfer and pre-processing device for point-of-care testing of AR.

July 1, 2019 by admin 0 Comments

A recyclable CNC-milled microfluidic platform for colorimetric assays and label-free aged-related macular degeneration detection

Authors
Samjin Choi(a, 1), Sang Woong Moon (b, 1), Seung Ho Lee (a), Wansun Kim (a), Soogeun Kim (a), Su Kang Kim (c) Jae-Ho Shin (b), Young-Guk Park (d), Kyung-Hyun Jin (b), Tae Gi Kim (b)
Abstract
We report the development of a simple, low-cost, and eco-friendly stand-alone 3D microfluidic chemical sensing platform capable of colorimetric and biochemical analyses at the same time. The microfluidic cellulose microfiber (μCM) chip was prototyped by injecting 10% CM mixtures on computer numeric control (CNC)-milled substrates. We show that the μCM chip has a 3-fold faster flow rate than conventional microfluidic paper-based analytical devices and is a recyclable platform that could perform basic microfluidic experiments.

December 1, 2017 by admin 0 Comments

Nanopillar-array architectured PDMS-based triboelectric nanogenerator integrated with a windmill model for effective wind energy harvesting

Authors
Bhaskar Dudem (a, 1), Nghia Dinh Huynh (b, 1), Wook Kim (b), Dong Hyun Kim (a), Hee Jae Hwang (b), Dukhyun Choi (b), Jae Su Yu (a)
Abstract
Triboelectric nanogenerator (TENG) is an up-and-coming technology that functions based on the triboelectrification and electrostatic induction to generate the electricity from various mechanical energy sources. However, the practical applications still demand a significant improvement of the TENG output performance, so the optimization of key factors such as triboelectric material selectivity, nanostructure-like morphology, and surface contact area is very crucial. Here, we reported a TENG based on nanopillar-array architectured polydimethylsiloxane (NpA-PDMS) layers with simple and cost-effective fabrication process, high output performance, and long-term stability. We mainly focused on improving the output performance of TENG by optimizing the structural dimensions of nanopillar architectures (NpAs) distributed on the surface of PDMS. The effect of output performance of TENG by varying the period and diameter of NpAs on the surface of PDMS was theoretically and experimentally investigated. For theoretical study, we considered the NpA-PDMS as a viscoelastic material. From this simulation, we calculated the contact stress for NpA-PDMS layers and compared the behaviors by considering the contact area and stress together (i.e., the product of contact area and stress, called as a contact force). Surprisingly, the calculated results were well matched with the experimental data. And, an optimal NpA-PDMS with the period and diameter of 125 nm and 60 nm, respectively, was formed. Thus, the TENG with the optimal NpA-PDMS exhibited the open-circuit voltage (VOC) and short-circuit current (ISC) values of ~ 568 V and ~ 25.6 μA, respectively, under 10 N of pushing force and 5 Hz of pushing frequency. Additionally, the enduringness test of the TENG device was also conducted to confirm its mechanical stability and durability. Finally, for a real application, the optimized TENG device was incorporated with a windmill system to effectively harvest the wind energy available in indoor and outdoor environments. This windmill system effectively harvested the wind energy, exhibiting the VOC and ISC values of ~ 200 V and ~ 24 µA, respectively, at the wind speed of 14–15 m/s.

August 1, 2017 by admin 0 Comments

Cam-based sustainable triboelectric nanogenerators with a resolution-free 3D-printed system

Authors
Younghoon Lee (a), Wook Kim (a), Divij Bhatia (a), Hee Jae Hwang (a), Sangmin Lee (b), Dukhyun Choi (a)
Abstract
Abundant rotating energies in our environment could be utilized to produce electrical power by using mechanical energy harvesters; however, rotating scavengers are limited by their low lifetimes and high costs due to the severe friction between operating materials and the necessity of precise system resolution. In this study, we report cam-based triboelectric nanogenerators (C-TENGs), where the cam transforms rotational motion into linear movement, resulting in a practically-sustainable high-performance scavenger that utilizes contact-type TENGs. Furthermore, we use bumper springs in the C-TENG system to create cost-effective and resolution-free C-TENGs, which allow the low-resolution system elements (i.e., 3D-printed components) to be easily rotated without experiencing blocking. It is demonstrated that the ratio between the spring constants of a spacer spring and a bumper spring is an important design variable to improve the output power of the C-TENG. Interestingly, we also find that the rigidity of the supporting substrate below the contacting materials is significant and enhance the output performance of TENGs over twice by adopting soft substrates. By augmenting the number of cam noses, the working frequency increases, but the output peak power is not changed due to the same contact velocity in the C-TENG. Alternatively, the output power in the C-TENG is extremely dependent on the angular velocity where the contact velocity significantly increases. We suggest that the contact velocity could be determined by analyzing the separation time in the C-TENG; this is useful because it is difficult to directly measure the velocity. Our C-TENG is demonstrated to produce a uniform high output voltage (~350 V) for a long time (over 210,000 cycles) at 400 rpm. The maximum output energy and average power of our C-TENG are calculated to be 6.7 µJ and 3.5 mW at 15 MΩ, respectively. The C-TENG is practically used to power 180 commercial green light-emitting diodes (LEDs) with a bicycle. We expect that this sustainable and resolution-free 3D-printed system design will be a practical and promising solution for industrial applications of TENGs.