• 한국기계가공학회지
• /
• 제21권7호
• /
• pp.77-83
• /
• 2022

When carbon dioxide in a liquid becomes supersaturated, carbon dioxide gas bubbles are generated in the liquid, and they ascend to the surface as they develop further. At this time, the inner wall of the cup with carbon gas attached is known as the entrapped gas cavity (EGS); once an EGS is established, it does not disappear and will continuously create carbon bubbles. This bubbling phenomenon can be activated or suppressed by changing the properties of the solid surface in contact with the carbonated liquid. In this study, the foaming of carbonated liquid is promoted or suppressed by modifying the wettability of the surface. A micro/nano surface structure is formed on the surface of an aluminum cup to produce a superhydrophilic surface, and a superhydrophobic surface similar to a lotus leaf is synthesized via fluorination. Experiment results show that the amount of carbon dioxide bubble generated differs significantly in the first few seconds depending on the surface, and that the amount of gas generated after it enters the stabilization period is the same regardless of the wettability of the cup surface.

• 한국음향학회지
• /
• 제29권4호
• /
• pp.251-257
• /
• 2010

본 논문에서는 액체 매질 내 기포운에 의한 초음파의 감쇠 및 분산 특성을 다룬다. 액체 내 기포운은 다양한 기작에 의해 발생되며 이에 따라 기포운을 구성하는 기포들의 크기와 분포가 다양한 양상을 가지게 된다. 따라서 기포들의 크기와 분포에 따라 기포운의 감쇠와 분산 특성이 어떻게 변화하는지에 중점을 둔다. 특히 아직 보고된 바 없는 나노 기포운의 감쇠 및 분산 특성에 대하여 조명하고자 한다. 수치해석 결과, 기포운의 음향 감쇠 및 분산 특성은 구성 기포들의 첨예도에 따라 크게 변화하는 것으로 나타났다. 본 연구는 기포운 내 음향 전파의 심도 있는 이해에 일조할 것으로 기대한다.

• 한국재료학회:학술대회논문집
• /
• 한국재료학회 2011년도 춘계학술발표대회
• /
• pp.3.2-3.2
• /
• 2011

In recent years, inkjet printing technology has received significant attention as a micro/nanofabrication technique for flexible printing of electronic circuits and solar cells, as well for biomaterial patterning. It eliminates the need for physical masks, causes fewer environment problems, lowers fabrication costs, and offers good layer-to-layer registration. To fulfill the requirements for use in the above applications, however, the inkjet system must meet certain criteria such as high frequency jetting, uniform droplet size, high density nozzle array, etc. Existing inkjet devices are either based on thermal bubbles or piezoelectric pumping; they have several drawbacks for flexible printing. For instance, thermal bubble jetting has limitations in terms of size and density of the nozzle array as well as the ejection frequency. Piezoelectric based devices suffer from poor pumping energy in addition to inadequate ejection frequency. Recently, an electrohydrodynamic (EHD) printing technique has been suggested and proposed as an alternative to thermal bubble or piezoelectric devices. In EHD jetting, a liquid (ink) is pumped through a nozzle and a strong electric field is applied between the nozzle and an extractor plate, which induce charges at the surfaces of the liquid meniscus. This electric field creates an electric stress that stretches the meniscus in the direction of the electric field. Once the electric field force is larger than the surface tension force, a liquid droplet is formed. An EHD inkjet head can produce droplets smaller than the size of the nozzle that produce them. Furthermore, the EHD nano-inkjet can eject high viscosity liquid through the nozzle forming tiny structures. These unique features distinguish EHD printing from conventional methods for sub-micron resolution printing. In this presentation, I will introduce the recent research results regarding the EHD nano-inkjet and the printing system, which has been applied to solar cell or thin film transistor applications.

• 공업화학
• /
• 제26권4호
• /
• pp.421-426
• /
• 2015

미세조류 Arthrospira platensis는 단백질 함량이 높고, 불포화 지방산 등을 다량함유하고 있어 건강보조식품 및 다양한 분야에서 활용되고 있다. 또한 phycocyanin, myxoxanthophyll, zeaxanthin 등의 색소를 함유하고 있어서 항산화물질, 식품 첨가물로도 이용되고 있다. 나노기포 수소수는 수소 기체를 나노기포 상태로 물속에 주입하여 포화용해도 이상으로 용해시킨 것이다. 이런 나노기포 수소수는 항산화능이 높고, 항암효과가 있는 것으로 알려져 있다. Arthrospira platensis를 일반 증류수 배지와 수소수로 제조한 배지에서 배양한 후 특성을 확인하였다. 배양 결과, 세포 성장 및 광합성으로 인한 색소인 chlorophyll과 carotenoid의 함량은 수소수 배지에서 배양하였을 경우 대조군에 비해 15% 정도 증가한 것으로 나타난다. 그리고 phycocyanin 역시 7% 정도 증가하였다. 하지만, 지질함량은 수소수 배지 배양과 일반 배지 배양 간에 큰 차이가 없는 것을 확인하였다. 항산화물질의 함량을 확인하기 위해 flavonoid 및 polyphenol의 함량을 측정하였다. Flavonoid는 수소수 배지에서 배양하였을 경우 대조군에 비해 70% 이상 증가함을 보이고 있다. 하지만 polyphenol은 대조군과 유사한 함량을 보이고 있다.

• 한국산학기술학회논문지
• /
• 제22권6호
• /
• pp.11-18
• /
• 2021

나노버블수는 태양광 패널 청소, 도로의 염분 제거, 기계의 정밀 부품 청소 등 다양한 세척 공정에 사용된다. 해양쓰레기 세척 시스템의 전처리에 나노버블을 적용하면 높은 세척 효율과 물 절약이 가능하다. 본 연구에서는 나노버블수의 염분 제거율을 비교하기 위해 NaCl 200,000 mg/L 용액에 목재를 침적시켜 해양쓰레기를 제작하였다. 수돗물과 나노버블수를 이용하여 노즐 종류, 오리피스 직경, 펌프 회전수 및 세척 시간에 따른 목재 표면 염분농도를 비교하였다. 목재 표면 염분농도는 세척시간이 길어질수록 감소하였다. 하지만 물 사용량을 고려한 최적의 세척 시간은 5-10초 사이였다. 노즐의 오리피스 직경이 커질수록 분사압력은 낮아지며, 세척 후 목재 표면 염분농도는 높아졌다. 이는 노즐의 오리피스 직경이 세척 시스템에서 중요한 요인임을 나타낸다. 나노버블수를 이용한 세척 후 목재 표면 염분농도는 수돗물로 세척 후 목재 표면 염분농도에 비해 부채꼴형 노즐은 2.2 %, 원형 노즐은 30.9 % 낮았다. 또한, 나노버블수를 이용한 세척 실험에서 부채꼴형 노즐을 사용하여 세척하였을 때가 원형 노즐을 사용하였을 때보다 목재 표면 염분농도가 약 9.5 mg/L 낮았다.

• 대한기계학회논문집B
• /
• 제27권2호
• /
• pp.236-242
• /
• 2003

Thermal bubbles find their diverse application areas in the MEMS (MicroElectroMechanial Systems) technology, including bubble jet printers, microactuators, micropumps, etc.. Especially, microactuators and micropumps, which use a microbubble growing by a controlled heat input, frequently involve mechanical and thermal interaction of the bubble with a solid structure, such as a cantilever beam and a membrane. Although the concept is experimentally verified that an internal pressure of the bubble can build up high enough to deflect a thin solid plate or a beam, the physics of the entire process have not yet been thoroughly explored. This work reports the experimental study of the growth of a thermal bubble while deflecting a thin cantilever beam. A physical model is presented to predict the elastic response of the cantilever beam based on the experimental measurements. The scaling law constructed through this work can provide a design guide for micro- and nano-systems that employ a thermal bubble for their actuation/pumping mechanism.

• 한국가시화정보학회지
• /
• 제9권1호
• /
• pp.17-19
• /
• 2011

The bubble oscillations play an important role in ultrasonic cleaning processes. In the ultrasonic cleaning of semiconductor wafers, the cleaning process often damages micro/nano scale patterns while removing contaminant particles. However, the understanding of how patterns in semiconductor wafers are damaged during ultrasonic cleaning is far from complete yet. Here, we report the observations of the motion of bubbles that induce solid wall damage under 26 kHz continuous ultrasonic waves. We classified the motions into the four types, i.e. volume motion, shape motion, splitting or jetting motion and chaotic motion. Our experimental results show that bubble oscillations get unstable and nonlinear as the ultrasonic amplitude increases, which may exert a large stress on a solid surface raising the possibility of damaging microstructures.

• 한국광학회지
• /
• 제20권3호
• /
• pp.182-188
• /
• 2009

완충용액과 분석시료의 확산으로 발생하는 측정 오차를 최소화하기 위하여 공기주입 장치와 공기제거 장치를 설치한 표면 플라즈 몬 공명 타원계측기(surface plasmon resonance ellipsometer: SPRE)를 새로이 제안하고 이를 제작하였다. SPRE에서 완충용액과 분석시료간의 상호 확산은 분석시료의 농도를 변화시켜 굴절률 측정에 영향을 주고, 이 결과 생체분자 물질의 접합 특성이 명확하게 나타나지 않는다. 이러한 SPRE의 측정 장치에 공기를 주입하는 장치를 추가로 설치하여 두 용액의 확산을 막고, 특히 불필요한 공기가 채널 내부로 유입되어 생기는 잡음신호를 없애기 위하여 공기제거 장치를 사용함으로써 신뢰성 있는 SPRE의 측정 결과를 얻을 수 있음을 확인하였다.

• 설비공학논문집
• /
• 제17권4호
• /
• pp.312-317
• /
• 2005

The objectives of this paper are to study the absorption characteristics of $NH_3$ bubbles in the binary nanofluids and to quantify the effects of surfactants and nano-particles on the bubble absorption performance. 2-Ethyl-1-Hexanol, n-Octanol, and 2-Octanol are used as the surfactants and nano-sized $Al_{2}O_3$ and Cu particles are added to make the binary nanofluids into $NH_3/H_{2}O$ solution. The concentration of $NH_3$ solution ($x_s$), the concentration of surfactants ($x_{SA}$), and the mass fraction of nano-particles ($w_{np}$) are considered as key parameters. The experimented ranges of $x_s,\;x_{SA},\;and\;w_{np}$ are $0{\sim}17.92\%,\;0{\sim}1,500\;ppm\;and\;0{\sim}0.2\%$, respectively. The absorption rates are calculated by measuring initial and final weights of test section and exposed time. In addition, the bubble absorption processes are visualized using the shadow graphic method. The results show that the absorption performance is significantly enhanced up to 4 times by adding the surfactants and up to 3 times in the binary nanofluids.

• 한국환경과학회지
• /
• 제20권10호
• /
• pp.1329-1336
• /
• 2011

The objectives of this study are to examine the processing of oils contamination soil by means of using a micronano-bubble soil washing system, to investigate the various factors such as washing periods, the amount of micro-nano bubbles generated depending on the quantity of acid injection and quantity of air injection, to examine the features involved in the elimination of total petroleum hydrocarbons (TPHs) contained in the soil, and thus to evaluate the possibility of practical application on the field for the economic feasibility. The oils contaminated soil used in this study was collected from the 0~15 cm surface layer of an automobile junkyard located in U City. The collected soil was air-dried for 24 hours, and then the large particles and other substances contained in the soil were eliminated and filtered through sieve No.10 (2 mm) to secure consistency in the samples. The TPH concentration of the contaminated soil was found to be 4,914~5,998 mg/kg. The micronano-bubble soil washing system consists of the reactor, the flow equalization tank, the micronano- bubble generator, the pump and the strainer, and was manufactured with stainless material for withstanding acidic phase. When the injected air flow rate was fixed at 2 L/min, for each hydrogen peroxide concentrations (5, 10, 15%) the removal percents for TPH within the contaminated soil with retention times of 30 minutes were respectively identified as 4,931 mg/kg (18.9%), 4,678 mg/kg (18.9%) and, 4,513 mg/kg (17.7%). And when the injected air flow rate was fixed at 2 L/min, for each hydrogen peroxide concentrations (5, 10, 15%) the removal percents for TPH within the contaminated soil with retention times of 120 minutes were respectively identified as4,256 mg/kg (22.3%), 4,621 mg/kg (19.7%) and 4,268 mg/kg (25.9%).