3D Printing of surface-area-controlled polymeric structures for removal of arsenic

김기훈 서강대학교 대학원 2018 국내석사

3D printing of moldless flexible pressure sensor using Bingham plastic

조수민 서강대학교 대학원 2018 국내석사

Devices made from stretchable electronic materials are under huge interest as future application for wearable device in means for clothing or directly attached sensor. Such materials have typically been prepared by engineering elastomeric materials such as silicon. With their flexible characteristic, the response to the external mechanical deformation have also drawn much attention. Here we studied 3D printed flexible and moldless fabricated pressure sensor. Using 3D printer to freely direct write resistance electrode, the extruded CNT/PDMS sensor was studied to verify whether the geometric structure influences the sensor’s sensitivity. Moreover, this methodology could substitute the complicated steps commonly used for fabrication of 3D structure or PDMS molding such as lithography or etching. The 3D printing of viscoplastic elastomer while maintaining its structure after extrusion without collapsing was possible when printing was proceeded inside the Bingham. In order to test the conductive composite’s response to external mechanical deformation, the gauge factor of CB/PDMS with different structure was studied. Afterwards CNT/PDMS as resistive electrode was printed for pressure sensor structure. The structure is uniformly aligned with independently arrayed deformable pyramidal tips that each of them works as a resistive sensor tip. The easily deformable pressure sensors are designed regarding the shape factor that effect the shape of elastomer as its compressibility in response to external pressure. The counter electrode was easily printed through commercial office printer using silver nanoparticle ink on PET film or Sonoplot. When the external pressure is introduced, a potential difference with respect to 3D printed resistive elastomer structure can induce electric current flow through the contact area by bridging the two electrode terminals. Three geometrically different pyramidal sensors were fabricated with different bottom square edge to height ratio to test the sensitivity variation through structure transition. The sensitivity and detection range of three sensors all differed from 0 to 1300 Pa. From this conclusion, the hypothesis that shape of sensor highly affects the sensitivity and detection range was confirmed.

Multi-functional end Group Chemical Gradient Modification Using Organosilane Self-Assembled Monolayers for Cellular Adhesion Studies

김현정 서강대학교 일반대학원 2011 국내석사

Gradient surface means gradual changes of chemical or physical property along one direction in one substrate. Gradient is powerful tool to reduce the efforts and time to prepare each individual different sample substrate. In this perspective, gradient can be applied to screening processes which you can find what property is the best for specific cases such as nanoparticle absorption on the gradient surface. From inorganic nanoparticle to cells and proteins consisting of lives, various high throughput screening tests are possible on the gradient surface. Herein methyl, carboxylic acid, and amine, these three functional groups were mixed on the surface directionally which called gradients via two different methods. One is solution diffusion method which the interface between two solvents diffuses as reaction time goes by and the other is thiol-ene radical reaction under UV. Both of methods provide gradient surfaces and these gradients can be utilized as a screening substrate for cellular adhesion study. Furthermore, these studies can be one of efficient tools to understand the cellular surface properties. 방향성을 가지고 화학적 또는 물리적인 특성을 하나의 기판 위에서 점진적으로 차차 변화시킨 표면을 gradient라고 한다. Gradient는 원하는 특성을 점진적으로 변화시킨 것이므로 각각 분리된 시편을 준비할 때에 드는 시간과 노력의 절감을 도모할 수 있다는 장점을 가진다. 또한 gradient를 적용함으로써 나노입자와 같은 무기물부터 세포, 단백질에 이르는 유기물들의 흡착특성 등을 알아보는 high-throughput screening 기술이 발전하고 있다. 본 논문에서는 다양한 농도구배표면 제작 방법 중에서 혼합 가능한 두 용액의 계면에서 농도차이에 의해 자연적으로 이루어지는 확산을 이용한 방법과 고에너지의 254 nm파장 광조사를 통한 thiol과 ene간의 radical반응을 이용하는 두 방법을 이용하여 원하는 작용기를 표면에 가지는 농도구배표면을 만들 수 있었다. 이렇게 만들어진 농도구배표면은 부착세포의 선호표면을 연구하는 기판으로 사용되었고, 다양한 세포를 screening하면 세포 표면 및 흡착 특성을 연구하는 데에 도움이 될 것으로 전망한다.

Characterization of stimuli-responsive polymer surfaces and devices

이주미 서강대학교 대학원 2018 국내박사

When external stimuli are given, they react reversibly or irreversibly to the external environment, causing structural changes at the interface of the material. Changes in the external environment control the energy of the material, and control the structure, thereby changing the physical or chemical properties of the material.

Design of Liposome-Based Nucleus Mimic System for DNA Amplification, Pore Formation and Controlled Release of Genetic Materials

허은진 서강대학교 일반대학원 2023 국내석사

The study of artificial cells plays an important role in understanding the functions and processes of cells. By studying artificial cells, researchers can create simplified model systems that mimic cellular components and processes to gain insight into key mechanisms and the origin of life. The nucleus is essential for overall cellular function and reproduction, which involves DNA replication and the release of genetic material to the external environment, so in this study tried to mimic the replication and release of genetic material. Advances in research have made it possible to replicate and release genetic material within artificial cells using techniques such as polymerase chain reaction (PCR) and creation of pores using pore forming materials have been studied to control the release of internal materials from artificial cells. In this study, we aim to replicate the DNA through PCR and create pores using azo lipids to mimic gene activity to perform complex mechanisms within artificial cells. We expect that this study will lead to advances in cell mimicry research and on understanding of the origin of life.

Preparation and characterization of gel polymer electrolyte-based lithium ion battery using a radiation technique

최지훈 서강대학교 대학원 2020 국내석사

In this research, the in situ formation of poly(vinylpyrrolidone based gel polymer electrolyte (PVP-GPE) inside LIB cell was studied by quicker and more efficient electron beam irradiation. For this purpose, a radiation sensitive GPE precursor solution was prepared by mixing VP as a monomer, PD as a crosslinker with a commercial liquid electrolyte, and gel behavior and electrochemical characterization were performed at various irradiation doses. The analytical results revealed that PVP-GPE was created by EB irradiation at the absorbed dose of 1 kGy (corresponding to th e irradiation duration of 3 seconds). The PVP-GPE-1 exhibited a gel fraction of 97%, good thermal stability, good electrochemical stable voltage window (2.0 ~ 4.7 V), and good ion conductivity. As a result, the in situ formation of PVP-GPE-1-based coin-type LIB cell showed the initial discharge capacity of 133 mAh/g, and its capacity retention at the cycle number of 50 was 69%, quite comparable to that with a liquid electrolyte (135 mAh/g and 72%). 본 연구에서는 상온 방사선가교반응을 이용하여 조립된 전지의 액상전해질을 겔 전환시켜 이차전지를 제조하고 전지의 성능평가를 수행하고자 하였다. 일정 조성비에서 1-Vinyl-2-Pyrrolidone (VP), Poly(ethylene glycol) diacrylate (PD), 1 M LiClO4 liquid electrolyte를 이용하여 방사선 민감성 전구체 조성물 를 제조하고 다양한 방사선 조사 조건하에 겔 거동 및 전기 화학적 특성 분석을 수행하였다. 형성된 겔 전해질의 특성 분석 결과 92 wt% 액상 전해질 을 함유한 겔 전해질 이 성공적으로 제조 되었고 액상전해질과 유사한 수준의 이온 전도도와 4.7 V 까지 전기화학적으로 분해되지 않고 안정함을 확인하였다. 최종적으로 겔 전해질 기반 코인셀 단위전지 적용 성능 평가 결과 방전용량은 상용 액상전해질 기반 단위전지에서 보고되고 있는 수준과 유사한 수준 으로 유지됨을 확인하였다.

Eco-friendly radiation-based preparation of Prussian blue-immobilized poly(4-vinylpyridine)-grafted non-woven fabric for cesium ion adsorption

홍랑기 서강대학교 대학원 2021 국내석사

본 연구에서는 환경친화적인 수용액에서 전자선 유도 접목중합을 통해 폴리 4비닐피리딘이 그라프트된 폴리프로필렌 부직포 (Poly(4-vinylpyridine)-grafted polypropylene, PP-g-P4VP)를 제조하였으며, 나아가 프러시안 블루의 고정화에 의한 다공성 부직포 흡착제를 제조하였다. 그라프트율과 그라프트 효율을 분석한 결과, 최적 조건(90 kGy의 조사선량, 120분의 반응시간, 3 wt%의 단량체 농도)에서 80% 이상의 효율을 갖는 원하는 그라프트율을 얻을 수 있음을 확인하였다. FT-IR, FE-SEM, XRD 기기를 이용한 화학적 구조, 형태학 및 결정 구조를 분석 결과 결정 입방 프러시안 블루 입자가 고르게 고정된 PP-g-P4VP-PB 흡착제가 성공적으로 제조되었음을 명확하게 확인하였다. 또한 제조된 PP-g-P4VP-PB는 흡착제에 적용하기에 적합한 우수한 인장 특성을 가졌다. 제조된 흡착제의 세슘 이온 흡착성능 평가 결과, 상업용 프러시안 블루 파우더보다 5분의 1의 낮은 프러시안 블루 함량을 가지면서도 응집과 침전을 최소화한 프러시안 블루가 균일하게 고정화된 PP-g-P4VP-PB 흡착제는 상업용 프러시안 블루 파우더와 유사한 흡착성능을 보임을 확인하였다. In this study, we newly reported that well-defined poly(4 vinyl pyridine)-grafted non-woven polypropylene (PP-g-P4VP) can be produced by electron beam-induced graft polymerization in ecofriendly water solvent and further used as an efficient cesium ion (Cs+) adsorbent by immobilization of Prussian blue (PB). The results of grafting degree and grafting efficiency reveals that the desired grafting degree of PP-g-P4VP with grafting efficiency above 80% can be obtained under the optimal conditions (adsorbed dose of 90 kGy, reaction time of 120 min and monomer concentration of 3 wt%) in aqueous solvent system. The successful preparation of PP-g-P4VP-PB with crystalline cubic PB was clearly confirmed using FT-IR, FE-SEM, and XRD. It also had a good tensile strength suitable for application to easy-to-handle adsorbent. Moreover, the results of Cs+ adsorption test revealed that the PR-g-P4VP-PB adsorbent even containing one-fifth lower amounts than use of PB itself exhibited the comparable adsorption performance to that of commercial PB powder possibly due to PB-evenly immobilized fibers minimizing the aggregation and precipitation of PB itself.

Fabrication of thermoelectric temperature sensors for paper-based microfluidic chip

채희도 서강대학교 2017 국내석사

최근에 랩온어칩(lab-on-a-chip, LOC)을 구현하기 위한 방법으로 종이에 미세유체칩을 제조하는 연구가 많이 진행되고 있다. 이러한 방식은 환경 친화적이고 간단하며 경제적인 방법이라는 점에서 큰 장점을 지닌다. 그러나 금 나노 입자의 합성, 단백질 결정화 및 중합효소 연쇄 반응(PCR)과 같은 화학 반응에서 시료를 가열하고 온도를 정확하게 제어하는 것이 점점 더 요구되고 있다. 기존의 미세유체칩 연구의 대부분은 외부 히터 및 온도 센서를 사용하여 이러한 과정들을 진행하였기에 시스템의 간소화에 어려움이 컸다. 특히 LOC를 이용하여 POC(point of care) 장치를 구현하는 것에는 더욱 어려움이 있다. 따라서 본 연구에서는 온도 제어가 가능한 미세유체칩을 만들기 위해 종이에 히터 및 온도 센서의 인쇄 제조가 연구되었다. 이를 위해 적절하게 제조된 PEDOT:PSS, MWCNTs 잉크의 제조를 연구하였고 이것을 스크린 프린팅 및 스프레이 프린팅과 같은 방식을 통하여 미세유체칩을 만드는 방법에 대해 연구하였다. 이 두 물질의 제벡계수는 은 나노 입자 (AgNP)로 구성된 금속 기반 전극을 상대 전극으로 이용하여 측정되었다. 제벡계수는 스크린 인쇄 된 PEDOT : PSS 및 MWCNTs에 대하여 각각 19.86μV/K 및 2.66μV/K였다. 재료의 특성을 분석한 후 미세유체칩과 센서가 같이 인쇄 제작되었다. PEDOT:PSS와 MWCNTs로 만든 온도센서와 히터는 가깝게 배치되어 시료가 오가면서 온도를 측정할 수 있도록 설계되었으며 시료가 전기습윤방식을 이용하여 미세유체칩의 길을 따라 이동할 수 있게 설계되었다. 온도 센서와 히터는 Labview 컨트롤러 프로그램에 의해 자동 제어되고 미리 측정된 기울기 및 절편을 이용하면 온도를 계산하여 나타낼 수 있다. AgNP와 인쇄된 PEDOT : PSS의 열전 패턴은 11.90 μV/K의 기울기를 보였으며, 절편은 -44 μV였다. MWCNTs로 인쇄된 패턴은 7.06μV/K, 절편은 -100μV였다. 센서의 성능은 실온과 100 ℃ 사이의 범위에서 ± 2 ℃의 오차로 일반적인 온도 변화를 감지하기에 충분하다고 할 수 있다.

Fabrication of inkjet-printed heaters and application for microfluidic polymerase chain reaction chips

Ly, Mai Nguyet 서강대학교 대학원 2021 국내석사

Inkjet printing deposits the resistive materials to form a patterned heater easily, quickly, and economically in high resolution on paper and flexible substrates, which can convert electric energy to thermal energy when current is applied, based on Joule heating effect. Up to our knowledge, inkjet-printed heater has recently been introduced for nucleic acid amplification test but limited to isothermal amplification with a single heating zone to provide only one constant temperature. Aiming to extend its usage for the conventional polymerase chain reaction (PCR) that requires different temperatures, here we present the fabrication of polyimide film heaters using Dimatix inkjet printer with aqueous conductive silver nanoparticle ink. For that, firstly we optimized the ink, design and printer setting to attain high consistency of heater quality. After thermal annealing at 250 oC, we characterized the material, electrical, and thermal properties of the printed heaters. To maintain durability when a high electrical load of current was applied, it was important to keep the number of printing layers at three. A typical U-shape heater, of which the average end-to-end resistance was at 28.166 +/- 0.893 Ohm in case of 0.40 mm / 0.40 mm stroke weight ratio of heating regions, had been investigated. For PCR application, we proposed a four-heating-zone system with two interdigitated U-shape heaters whose stroke weight ratios were 0.45 mm / 0.35 mm, and 0.45 mm / 0.25 mm, after optimization. Target temperatures were obtained after 15 min when using with a temperature controller. This four-heating-zone system could maximize the number of thermal cycles on a limited area of PCR chip when we combined with corresponding flow channel design. By using xurography, we had prototyped a continuous flow microfluidic device with polydimethylsiloxane (PDMS) 5:1 for testing efficiency of our four-heating-zone system and set up a platform to measure, control, and analyze the result of PCR amplification.

3D printing of surface-area-controlled polymeric structures for removal of arsenic

김기훈 서강대학교 2018 국내석사

During the last decades, arsenic poisoning has been recognized as a worldwide problem. The threat of arsenic contamination to public health in developing countries is far more serious due to their high dependence on natural water sources. Many technologies for arsenic removal have been investigated and developed. However, because of the absence in rural areas of an infrastructure for large-scale water treatment, the filtering process, if it is to be successful, should be low-cost, small-scale, easily customized, and capable of being operated without electrical power. In this thesis, we introduce the first water filtration system for arsenic removal which was fabricated by three-dimensional (3D) printing technique. 3D printing itself can provide a compact and customized filtration system that meets the above-mentioned requirements and is made with abundant plastic materials. Moreover, due to the versatility of 3D printing, the internal surface area of the filters can be controlled to increase arsenic adsorption during filtering under atmospheric conditions. We investigated the effect of a controlled surface area on the flow rate and the deposition of the adsorbent, which are directly related to the adsorption of arsenite ions. To describe the arsenic adsorption on our 3D printed filtration system, we conducted batch, isotherm and column studies. We expect that this novel approach can be applicable to take advantage of architecture differences for various fields.