NANO KOREA 2020



A novel microfluidic platform for recovery of non-wetting Newtonian characteristics of GALINSTAN? using gas permeable PDMS membraneGil-dong Hong1, Dong-Weon Lee1*1School of Advanced Materials Science and Engineering, Saaa University, City Zipcode, Country7027421021715※ Text Page Limit: 1 page with single space00※ Text Page Limit: 1 page with single spaceGalinstan?, a non-toxic metal eutectic alloy, is in liquid phase at room temperature and has been investigated for various applications including biology [1], RF micro switch [2] and tunable frequency selective surface (FSS) [3]. However, its surface is readily oxidized in air environment and forms a thin oxide layer causing the alloy to adhere to almost any surface [4]. It was reported that Galinstan? behaves like true liquid in the below 1 ppm of oxygen environment [5], but this requires good hermetic packaging for microfluidic platform for Galinstan?. Microfluidic channels filled with diluted hydrochloric acid (HCl) showed removal of oxide skin in eutectic GaIn alloy [6], but such HCl filled microfluidic channel may not be applicable for most applications. We reported a super-lyophobic PDMS micro-tunnel using hierarchical micro/nano surface textured inner walls to manipulate “oxidized” Galinstan? droplet [7]. Although there have been several efforts [5-7], up to this point there is no simple, yet universally applicable microfluidic platform technology that maintains non-wetting Newtonian fluid characteristics of Galinstan?. In this paper, we report a novel microfluidic platform using gas permeable polydimethylsiloxane (PDMS) membrane and integrated HCl reservoir to constantly maintain non-wetting Newtonian fluid characteristics of Galinstan? in the microfluidic channel. We found that a simple technique using PDMS membrane on top of the HCl reservoir allows permeation of HCl vapor and transforms oxidized viscoelastic phase Galinstan? into non-wetting Newtonian true liquid phase Galinstan? (Fig.1). Various thicknesses (0.25, 0.5, 1 and 2 mm) of PDMS membranes and various concentrations of HCl (37, 30 and 25 wt%) solutions in air environment were tested. Fig. 2 shows 7.8 μL Galinstan? droplet’s contact angle changes over time for different PDMS membrane thickness. Fig. 3 shows Galinstan? droplet’s contact angle changes over time for different HCl concentrations. As expected, thinner PDMS membrane and higher HCl concentration solutions allow higher contact angle changes. It was found that HCl solution higher than 30 wt% with < 1mm PDMS membrane make the Galinstan? droplet’s contact angle increased and saturated within 100 seconds and allows recovery of its Newtonian fluid characteristics. We fabricated a microfluidic channel with a ‘T’-junction with integrated HCl reservoir all in replicated PDMS using SU-8 mold (Fig. 4). The device comprised a straight 500 μm wide channel, a 250 μm wide serpentine shape control channel, and 3 ports to inject Galinstan? and apply air pressure. The PDMS microfluidic channel and the PDMS HCl reservoir were bonded with another PDMS membrane (500 ?m thick) in between (Fig 4g). Fig 5a shows top view of the fabricated platform for Galinstan? microfluidics. As pointed, Galinstan? oxidizes instantly as it is exposed to air. Fig. 5b shows oxidized Galinstan? in the microfluidic channel which clearly shows its viscoelastic characteristics of oxidized Galinstan? which wetted the inner wall surface of the PDMS microfluidic channel. However, Galinstan? in this microfluidic channel quickly recovers its non-wetting true liquid phase Newtonian fluid characteristics due to HCl vapor diffusion (Fig. 4h and Fig. 5c) and subsequent reaction with oxidized Galinstan?. We also successfully demonstrated generation, merge and separation of Galinstan? slugs using this novel microfluidic platform. Fig. 6a shows a series of still images taken from a video showing a method of generation of Galinstan? slug with on-demand control of air pressure. Fig. 6b shows multiple Galinstan? slugs generated in a channel. We believe that this novel microfluidic platform for recovery of non-wetting Newtonian true liquid phase Galinstan? may unleash full potentials of a wide variety of liquid metal based applications.*Corresponding Author: Tel. +82-(31)-200-xxxx, E-mail.: abcd@efg.eduReferencesM. Knoblauch et al., Nature Biotechnology, 17, 906, 1999.P. Sen, C.-J. Kim, J. MEMS, 18 (5), 990, 2009.[3] M. Li, B. Yu, N. Behdad, IEEE Microwave and Wireless Component Letters, 20 (8), 423, 2010.[4] F. Scharmann et al., Surf. Interface Anal., 36, 981, 2004.[5] T. Liu, P. Sen, C.-J. Kim, IEEE MEMS Conference, 560, 2010.[6] M. Dickey et al., Adv. Functional Materials, 18, 1097, 2008.[7] D. Kim, D-W Lee, W. Choi, JB Lee, IEEE MEMS Conference, 1005, 2012.3041650-6350-1270013335023495-76200Oxidized Galinstan? droplet020000Oxidized Galinstan? droplet1240155-130175True liquid phase Galinstan? droplet020000True liquid phase Galinstan? droplet2987675-14287500-72390-142875005124450133350Microfluidic channel00Microfluidic channel36258501333500032721551022350Si00Si3272155133350Si00Si45212006985000448500569850PDMS00PDMS350710569850SU-800SU-816154401270000021971007620000452120012065000358140011430000869950114300Thin PDMS membrane(0.25, 0.5, 1, 2 mm)020000Thin PDMS membrane(0.25, 0.5, 1, 2 mm)19939001206505 ?L HCl solution(25, 30, 37 wt%)0200005 ?L HCl solution(25, 30, 37 wt%)-11811057150Figure 1: Oxidized Galinstan? droplet turned into true liquid phase Galinstan? droplet by chemical reaction with HCl vapor diffused through the PDMS membrane. 00Figure 1: Oxidized Galinstan? droplet turned into true liquid phase Galinstan? droplet by chemical reaction with HCl vapor diffused through the PDMS membrane. 50736500HCl reservoir00HCl reservoir560070088900PDMS + PDMSbonding00PDMS + PDMSbonding-7620050800-190525400Oxidized 00Oxidized 192405038100True liquid phase 00True liquid phase -1200152540000405638095250Galinstan? in channel00Galinstan? in channel19462756350000923925889000066210239370※ Image Page Limit: 1 page with single space00※ Image Page Limit: 1 page with single space4946650222250HCl reservoir integrated microfluidic channel00HCl reservoir integrated microfluidic channel287401017780Figure 4: Fabrication sequence of the HCl reservoir integrated microfluidic platform for Galinstan?: (a),(d) SU-8 mold, (b),(e) PDMS coating, (c),(f) replicated PDMS, (g) PDMS-PDMS bonding, (h) HCl vapor diffusion through the PDMS membrane.00Figure 4: Fabrication sequence of the HCl reservoir integrated microfluidic platform for Galinstan?: (a),(d) SU-8 mold, (b),(e) PDMS coating, (c),(f) replicated PDMS, (g) PDMS-PDMS bonding, (h) HCl vapor diffusion through the PDMS membrane.3019567238361301942516510000-1073158255Figure 2: Galinstan? droplet contact angles as a function of diffusion time of 37 wt% HCl for various PDMS membrane thicknesses.00Figure 2: Galinstan? droplet contact angles as a function of diffusion time of 37 wt% HCl for various PDMS membrane thicknesses.-3064666841-6985010858500205740064135002197100254635001191895159385True liquid phase for 30 and 37 wt% HCl00True liquid phase for 30 and 37 wt% HCl4077335160655‘Dewetting’020000‘Dewetting’4161790264795HCl vapor diffusion for 100 seconds020000HCl vapor diffusion for 100 seconds4612005100965003054350218440Oxidized 020000Oxidized 5201285101600True liquid phase020000True liquid phase1134110254635Oxidized even after 1000sdiffusion for 25 wt% HCl00Oxidized even after 1000sdiffusion for 25 wt% HCl2343150121285003016885281305Figure 5: (a) Top view of the HCl reservoir integrated microfluidic platform , (b) oxidized Galinstan? in the channel, and (c) true liquid phase Galinstan? after HCl vapor diffusion. 00Figure 5: (a) Top view of the HCl reservoir integrated microfluidic platform , (b) oxidized Galinstan? in the channel, and (c) true liquid phase Galinstan? after HCl vapor diffusion. -40005133985Figure 3: HCl concentration dependency of Galinstan? droplet contact angles for various HCl concentrations. 00Figure 3: HCl concentration dependency of Galinstan? droplet contact angles for various HCl concentrations. -12001526098500431165013335101600133352349548260(a)00(a)-1657351055370Figure 6: (a) A series of still images taken from a real-time video of generation of a Galinstan? slug by on-demand control air pressure through three ports, (b) generated multiple Galinstan? slugs. 00Figure 6: (a) A series of still images taken from a real-time video of generation of a Galinstan? slug by on-demand control air pressure through three ports, (b) generated multiple Galinstan? slugs. 4276725864235(b)020000(b)416877595885Generated Galinstan? slugs020000Generated Galinstan? slugs ................
................

In order to avoid copyright disputes, this page is only a partial summary.

Google Online Preview   Download