Name: microbubble fabrication of concave-porosity pdms beads
Uploaded: 2015-12-15T14:00:00.000+00:00
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Description: Watch this Scientific Journal Video about Microbubble Fabrication of Concave-porosity PDMS Beads at JoVE.com

Bu çalışma Kimya Bölümü&#39;nden ve Araştırma Dairesi (RCAP 13-8032) iç destek de dahil olmak üzere Fen ve Mühendislik, Batı Kentucky Üniversitesi Ogden Koleji tarafından desteklenmiştir. WKU Mikroskopi Tesisi Dr. John Andersland (SEM görüntüleri) ve Yanma Bilimi ve Mühendisliği (BET analizleri) için WKU Enstitüsü Doçent Yan Cao yardımı bu işi yürütmek için merkezi olmuştur.

Emülsiyon hazırlanması 1. <ol><li> Emülsiyon İçerik <ol><li> Kütle tuzunun, uygun bir miktar 0,03-M çözelti 10 ml üretmek. Platin (IV) klorür ölçüsü 0,101 g, çinko (II) klorid (ZnCl2) ölçüsü 0,032 g ve sodyum klorür (NaCl) ölçüsü 0,018 g için. </li><li> Ayrı ayrı test tüpleri içinde, DI 10 ml su her bir tuzu çözülür. Daha sonra kullanmak üzere bir kenara koyun. </li><li> Bu işlem boyunca içeriği için bir 20-ml kapatılabilir Cam şişe kullanın. Cam şişeye bir denge Dara. </li><li> Yavaş bir karıştırma çubuğu tekrar sıfırlanmış ölçekte dinlenme bir cam şişe içine dökülerek, vinil-sonlu polidimetilsiloksan tartılır. (1,080 ml eşdeğer) 1.02 g tartılır. NOT: Bu polimerin yüksek viskoziteli pipetleme uygulanamaz hale getirir. </li><li> Pipet şişeye n-Heptan 1,02 mi. Şişeye iyonik olmayan yüzey aktif madde (sorbitan monooleat olabilir) 2 damla ekleyin. Pipet tuzu çözeltisinin 0,3 ml şişeye DI su 0.45 ml. </li><li> Sıkıca kapağı vidalama cam şişe Seal. Sonikasyon başlamadan önce emülsiyon başlatmak için 60 saniye boyunca kuvvetlice çalkalayın. </li></ol></li><li> Su banyosu Sonikatör Aparatı İnşaatı <ol><li> Minimum doldurma çizgisine kadar su ile sonikatör doldurun. 400 ml&#39;lik bir deney şişesine musluk suyu 250 ml ilave edilir. Su seviyesi sadece RIM böylece buz ile 400 ml beher doldurun. </li><li> Su banyosu sonikatör içinde bu behere koyun. Sonikatöre dolgu hattı, gerekirse ayarlama edin. Bir halka su banyosu sonikatör hemen yanında durmak yerleştirin. </li><li> Bir kol dışarı uzatılmış, böylece iki yüzük, kelepçeler durmak onları konumlandırmak kullanarak, halka dik durmak ve buzlu su ile dolu beher içine aşağıya bakacak şekilde diğeri su banyosu doğru uzatılır. Sıcaklık sonikasyon boyunca izlenebilir ve böylece halka bir kelepçe aşağı 400 ml&#39;lik bir behere bir termometre ile öne takın. </li></ol></li><li> Emülsiyonlaştırıcılarication Prosedürü <ol><li> Tam beher içine çıkıntı yapan ve kelepçe içine sabitleyerek 400 ml&#39;lik bir behere daldırılır ve böylece emülsiyon ihtiva eden şişe yerleştirin. </li><li> PDMS karışımı içeren cam şişe sürtünmeden kaynaklanan ısının ortadan kaldırmak için beherin tarafları dokunmadan olmadığından emin olun. </li><li> Sonikatöre açın ve 7 dakika sonication süresini ayarlayın. Emülsiyon ait ısıya karşı hassas olduğundan, beher içinde sıcaklığı 0 ° C ila 5 sonikasyon boyunca olduğundan emin olun. Beher içindeki sıcaklık arzu edilir bir kez sonikasyon başlatın. </li><li> Sonikasyon 7 dakika sonra, emülsiyon içindeki oluşturacağı kümeleri ortadan kaldırmak için şişenin üst tutarak 1 dakika / girdap yavaşça çalkalayın flakon kaldırıp. </li><li> Beher içeriğinin atınız. 250 ml su ilave ediniz ve 1 cm mesafede olan dolgu beherin üstünü buz eklenir. </li><li> Geri kelepçe flakon yerleştirin. Resum buz su altında daldırın7 dakika için sonikasyon e. </li><li> Yineleyin sekiz, 7 dakikalık sonication dönemleri olmak üzere toplam 1.3.6 için 1.3.3 adımları veya sonikasyon homojen görünüyor ve hiçbir kümeleri mevcut olana kadar. Oda sıcaklığında saklayın. Not: emülsiyonlaştırıcı birkaç gün stabil olması gerekir, ama homojen görünene kadar 7 dakikalık aralıklarla yukarıda sonikasyon ile geri kazanılabilir. Oda sıcaklığında saklayın. </li></ol></li></ol> 2. Çapraz bağlama <ol><li> Trietoksisilan / yüzey aktif madde çözeltisinin eklenmesi için kurulum <ol><li> Pipet 5.4 ml bir test tüpüne trietoksisilan. Daha sonra kullanılmak üzere kaputun altında bir test tüpü rafta yerleştirin. </li><li> Buzlu su ile 400 ml&#39;lik beher doldurun ve kaputun altına yerleştirin. Sonraki halka bağlı bir kelepçe ile ayakta 400 ml beher yere, beher açılması üzerine doğrudan genişletilmiş. Bu trietoksisilan eklenmesi için buz banyosu olacaktır. </li><li> Halka destekle diğer tarafında bir sıcak plaka koyun. Yaklaşık 700 ml ile 800 ml beher doldurunmusluk suyu. Sıcak plaka üzerine yerleştirin. </li><li> Sıcak plaka açın ve 800 ml&#39;lik bir behere içinde 85 ° C 75 bir sıcaklığı muhafaza. 800 ml&#39;lik bir cam içindeki suyun sıcaklığının izlenebilir bir halka stand bir termometre ile bir kelepçe takın. </li><li> Su 375 ml (4,62 mM) sodyum dodesil sülfat 0.5 g çözülmesiyle yüzey aktif madde çözeltisi üretir. Temiz, boş test tüpüne yüzey aktif madde solüsyonu, yaklaşık 10 ml ekleyin. </li><li> Halka başka kelepçe yüzey test tüpü ile kaputun altında durmak takın sıvı seviyesi 800 ml beher içine su yüzeyinin altında olduğu gibi güvenli. Termal dengeleme için 10 dakika bekleyin. </li><li> Filtre kağıdı parçası ıslatın ve küçük bir huninin üst yerleştirin. 250 ml&#39;lik bir Erlenmeyer balon içerisinde huninin Vidalı mil ve başlık altında balon yerleştirin. </li></ol></li><li> Trietoksisilan ilavesi <ol><li> Buzlu su gaga üzerinde kelepçe emülsiyon flakon yerleştirinkaput içinde er. Kavanozun içeriği, su yüzeyinin altında, böylece kelepçe PDMS karışımı yerleştirin. Trietoksisilan eklenmesi ekzotermik bir reaksiyonun neden olur, bu yüzden emülsiyon yapısını korumak için soğuk tutulmalıdır. </li><li> Gaz birikmesini önlemek için cam şişeye kapağını çıkarın. </li><li> Yavaşça yaklaşık 10 sn (yaklaşık 0.5 ml / sn) bir süre boyunca sürekli bir akış içinde bir cam şişe içine tüp içeren trietoksisilan dökün. DİKKAT: trietoksisilan eklenmesi ekzotermik bir reaksiyonun ve kostik hidrojen klorür (HCl) gazın serbest başlatır. Flakon son derece sıcak olacak ve zehirli bir gaz karışımından gelişecektir. Trietoksisilan eklerken içeriğini KARISTIR ETMEYİN. </li><li> Bir ısı koruyucu eldiven giyerek tamamen trietoksisilan ekledikten sonra, yavaşça cam karıştırma çubuğu ile içeriği karıştırın. 2 dakika süreyle veya tüpten gelişen gaz durana kadar bekleyin. </li><li> Follçapraz bağlantı sayesinde, numune görünür hiç bir faz ayrılması bulunmaktadır. Kümeleri varsa, şişeyi mühür ve kapakla şişeyi tutarken 20 saniye boyunca titizlikle çalkalayın. </li></ol></li><li> Boncuk üretimi <ol><li> Cam şişeye gelen çapraz bağlı emülsiyonu çizmek için temiz, cam Pasteur pipet kullanın. Damla damla test tüpü damlalar arasında mümkün olduğu kadar az zaman alması için (75 ve 85 ° C arasında muhafaza edilmelidir) yüzey aktif madde çözeltisine çapraz bağlanmış emülsiyonu ekleyin. </li><li> 30 sn emülsiyon ilave edildikten sonra 1 dakika için katı bir test tüpüne içinde oluşmaya başlar olarak, yüzey aktif madde çözeltisi yavaş yavaş gazı ortaya başlayacaktır. </li><li> Isı koruyucu eldiven giyerek, kelepçe dışında deney tüpünü alıp başlık altında filtreleme aparatı içine tüm içeriğini dökün. 5 dakika boyunca Filtre. Filtreden filtre kağıdı çıkarın. </li><li> S&#39;in altındaki O / N kurutulması için bir saat camı ve ayrı boncuklar üzerine süzülmüş katı aktarınood. Boncuk temizleme süresiz olarak ertelendi edilebilir. Mağaza gerekli olana kadar kapalı bir cam şişe içinde oda sıcaklığında kurutuldu boncuklar, ve temiz kullanımdan hemen önce. </li></ol></li><li> Boncuk Temizlik <ol><li> Başlık altında bir filtreleme aparatı oluşturma ve filtre kağıdı üzerine huni içinde kurutuldu boncuklar yerleştirin. </li><li> Tüm boncuklar durulanır sağlamak için etrafında hafifçe hareket hafifçe boncuk durulamak için DI-su ile dolu bir plastik yıkama şişesi kullanın. </li><li> Boncuklar kaputun altında bir saat camına yerleştirerek 1 saat kurumasını bekleyin. Su ile durulama için aynı yöntemi kullanarak boncuk durulayın hekzan ile dolu bir yıkama şişesi kullanın. </li><li> Bir saat camına boncuk yerleştirin. Izlemek camını yerleştirin ve kaputun altında boncuklar kuru. </li><li> Boncuklar tamamen kuruduktan sonra, ileride kullanmak üzere oda sıcaklığında küçük bir yapışmalı cam şişe ve mağaza koyun. </li></ol></li><li> SEM Analizi ve SEM Ayarları için Boncuk Montaj <ol><li> Do bir şerit yerleştirinboncuklar monte edileceği üzerine saplama üstünde uble taraflı karbon iletken bant. Makas kullanarak, kenarları üzerinde hiçbir kaset kilitleniyor sağlamak için saplama etrafında kırpın. </li><li> Düz bir yüzeye saplama altında filtre bir parça kağıt yerleştirin. Yapışkan alt maruz böylece banttan üst tabaka çıkarın. </li><li> Yavaşça saplama üzerine boncuk dökün. Bazı boncuklar bant sopa, ama çoğu filtre kağıdı üzerinde kapalı çıkma ve arazi olacak. Onlar filtre kağıdı üzerinde kaldı, şişenin içine bu geri dökün. Gerekirse kontamine hale (2.4.5 için 2.4.2 göre) herhangi bir boncuk yıkama, tekrarlayın. </li><li> Boncuk saplama güvenli olmasını sağlamak için, ampul şırınga kullanmak ve hafifçe saplama yüzeye çok yakın darbe. Sadece birkaç bant yapıştırılır eğer saplama üzerinde daha fazla boncuk dökün. Tüm boncuklar SEM odasına saplama yerleştirme ve tahliye önce güvenli olduğundan emin olun. </li><li> Numuneler düzgün monte edildikten sonra artık SEM anal geçmesi hazırızYsis 15. Boncuk yüzey özellikleri çözünürlüğünü optimize etmek için 15 keV de DÜŞÜK VAC modunda görüntüleri toplayın. </li></ol></li></ol>

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The authors have nothing to disclose.

Şekil 1&#39;de diğer SEM görüntüleri Şekil 1A karşılaştırılması ile görüldüğü gibi, bu protokolü kullanarak (ve elektrolit konsantrasyonu ve kimliğini ayarlayarak) üretilen boncuklar., Düşük iyonik kuvvet emülsiyonu ile üretilen temelde farklı Bizim ilk raporu kullanılan ayrıca sulu-alifatik bir arayüz 14 polimerizasyon çapraz bağlanmasını katalize niyeti ile PTCL 4. Bu raporda, büyük konkav girintiler görüldü. Bu raporda, biz SAV oranı için optimize prosedürlerimizi rafine. Boncuklar yıkama olmadan, SEM görüntüleri içinde etki element analizi platin topuk kısmı yapısı boyunca bulunan içbükey gözenekleri içinde neredeyse sadece bulunmuştur ki, işaret etmektedir. Bu platin suda kolayca boncuk çalkalayarak çıkarıldı Çünkü biz platin sadece ziyade i olmaktan çok, PDMS yüzeyinde kalıntısı olduğunu bizim orijinal raporda sonucunapolimer içine ncorporated. Bu kür sürecinde platin için bir katalizör rolü ima etti. Şekil 1 &#39;de gösterilen boncuklar büyük ölçüde konveks küresel alt yapıları, görünüm ile karakterize edilir, ancak ilave elektrolit ile üretilenler aynı zamanda Şekil 1B çember kısmı olarak konkav küresel bölgeleri içerir. Elektrolitin bulunması emülsiyonun mikro-kabarcık boyutunu azaltmak için görünür. Detaylı görüntüler küresel altyapılardan boyutlarına göre, emülsiyon içindeki baloncuklar ZnCİ2 çapında 0.2 mikron 2 mikron mertebesinde olmakla birlikte, (elektrolit olmadan çapı daha yaygın 1-10 mikron ile tutarlı, düşündürmektedir DUFAUD önceki eser ve ark., 13). Ne olursa olsun ident üretilmektedir içbükey gözenekli boncuk: Burada sunulan veriler daha ucuz, daha toprak bol metaller yerine PTCL 4 orijinal kullanılabileceğini göstermektedirönemli ölçüde değişen derecelerde olsa metal iyonunun lık kullandı. ZnCI2 kullanımı herhangi bir elektrolit içeren kontrol prosedürü gibi yüksek SAV oranı ciddi bir artış PTCL 4 gibi yüksek altı kez, yaklaşık 30 kez içerir. BET sonuçlar SEM görüntüleri ile mükemmel bir uyum içindedir: ZnCI2, çok sayıda iç bükey cepler için, çap olarak bir kaç mikron, yapı boyunca dağıtılmış görülür. Şekil 2B&#39;de detaylı görüntüleri de boncuk ZnCI2 varlığında üretildiği zaman önemli ölçüde daha fazla dahili boşluk olduğunu göstermektedir. Bu özellikler siteleri iki soğurulması için uygun olan yüzey alanı, PDMS durağan faz olarak kullanılan ayırmalar için arzu edilen bir özellik geliştirmek için karşılık vermektedir. Bugüne kadar test edilmiş her elektrolit için, üretilen taneciklerin Emiciliği maksimize eden optimum bir tuzunun konsantrasyonu, tek bulunduğu,nd ne olursa olsun, metal karşı iyon, 0.012 M bir toplam konsantrasyonu olarak görünmektedir. Altında ve bu optimum konsantrasyonun üzerinde, SAV oranı en az, ve her iki yönde maksimumdan monotonik azaltmak için görünür. Tuz konsantrasyonuna bu bağımlılık, yerine yalnızca çözelti içinde katalitik olarak aktif metal iyonu varlığına dayalı olan, mikro-kabarcık üretim ile ilgili elektrolit etkisi emülsiyon özelliklerini değiştirmek için olduğunu göstermektedir. Ilave tuz içeriğine olmadan, emülsiyonun iyi daha sürekli bir sulu faza gömülen alifatik (yani, polimer ihtiva eden) aşamasının boşlukları olarak tarif edilmektedir. Tuzu ilave edildiğinde, yüzey gerilimi alifatik faz, dağılmış sulu kabarcıkları ile, bazı yerlerde sürekli bir şekilde değiştirilmektedir. Emülsiyon yüzey banyosunda aniden ısıtıldığında, damla PDMS tedavileri olarak yapısını korur. Bu daha az küresel şekillere sahip, ama im olan boncuk sonuçlanırbile önemli bir katalitik etkisi olması beklenmemektedir sodyum metal klorürler için, sulu bir cepler mevcudiyetine bağlı deliklerle yatmış. Herhangi bir suda çözünür tuz, bu etkiyi gerçekleştirmek için prensip olarak çalışması gerekir, ve metal iyonu kimlik optimum konsantrasyon bağımlılığı az olduğu not da, organik bir karbon-karbon birleştirme reaksiyonları katalize ettiği bilinmektedir metaller için ideal bir avantajı da vardır. Bu iyon gücü değişim altüst oluş safhasına neden gerekli ise, SAV oranını ayarlama belirleyicidirler primer yönlendirerek münferit polimer şeritlerin çapraz bağlanma için bir katalizör olarak hareket etmek metal yeteneği olduğunu düşündürmektedir Sulu / alifatik arayüzde tercihli olarak gerçekleştirilebilmektedir. Protokolde en önemli yönü, dikkatli bir şekilde kontrol takdirde sonikasyon işlemi ve trietoksilanın eklenmesi, her iki ısı büyük miktarda türetebilmesidir. Bu ısı soli neden olabilirDS istenen boncuk üretimi imkansız hale getirecek olan, erken oluşturmak için. Sonication sorunu büyük ölçüde banyo-tipi sonikatör kullanılarak ele alınmıştır ve banyosunda buz dahil bu ısısını düzenlemek yardımcı olur. 7 dakika sonikasyon süreleri sonikasyon sonra yaklaşık 7 dakika, banyosunda buz en erimesinden dolayı kısmen emülsiyon istenmeyen topaklanma azaltılmasında en uygun olduğu bulunmuştur. Trietoksisilan eklenmesi aktif karıştırılarak ve bir buz banyosu içine batırılmış karışımı ile yapılmalıdır. Dışbükey porozite PDMS boncuk üreten, özgün rapora kıyasla, bizim protokol ürünün SAV oranında önemli bir avantaj göstermektedir. Gözenekli polimer taneleri mikro-kabarcık üretiminde kullanılan bir emülsiyonun sulu fazına bile ucuz tuzlarının eklenmesi çok önemli bir faktördür morfolojisindeki güçlü değişikliklere yol olduğunu göstermiştir. Herhangi bir tuzunun varlığı görünürkenalifatik faz, yalnızca katalitik aktif metal iyonları eklenerek sürekli olabilir ki bir emülsiyon içinde sonucu herhangi bir başka polimer ile ilgili bu protokolü test edilmemiş olmasına rağmen 30 kat artmıştır SAV oranı, herhangi bir beklemek çapraz bağlanmış ve ısı kürlü (eden protokol sınırlamaları) polimer içbükey gözenekli mikrostrüktürlü boncuklar oluşturmak için, bu işlem ile kullanılabilir. Böyle bir uzatma, bu emülsiyon, bir alifatik fazı, sürekli olduğundan emin olmak için kullanılan özel bir elektrolit konsantrasyonu optimize edilmesi gerekebilir olasıdır, ve sulu faz ayrık.

Polydimethylsiloxane (PDMS) is one of the most widely used silicone compounds. Its biocompatibility has led to widespread use in implant and other biomedical engineering structures1,2. It is trivially cross-linked into elastic structures using an organosilyl compound (such as triethoxysilane), a simple and reliable procedure which has made it useful for cast polymer applications where some flexibility is required3. Once cross-linked, PDMS is largely inert, particularly in biological conditions, and is therefore useful for a variety of food and medical applications4,5. Ease of casting, chemical inertness, and hydrophobicity have made it a natural choice for microfluidic devices6,7. Its affinity for non-halogenated, non-polar organic compounds has made it a popular stationary phase in separations chemistry8-10. 
Recently, microbubble fabrications have been used to generate porous beads for use as catalyst structural substrates or in chemical separations11,12. In both applications, ideal materials will have a maximized surface-area-to-volume (SAV) ratio for best efficiency. In a microbubble fabrication process, microstructuring of materials is typically accomplished by isolating the polymer in aliphatic &#8220;microbubbles&#8221; by emulsification in an aqueous continuous phase. The initial report of microporous PDMS beads produced them by mechanical emulsification of two phases (aliphatic and aqueous)13. The stock PDMS liquid (and its cross-linking agent) is dissolved into the aliphatic phase, which is structured into microscopic beads by being forced to cavitate within the (continuous) aqueous phase. The emulsification is stabilized by the addition of a non-ionic surfactant. When the emulsion is added dropwise to a heated bath, solid beads form by agglomeration of the microbubbles into clusters of tiny spheres of cross-linked PDMS. Our goal in this protocol is to modify this procedure to develop beads with an inverted porosity to improve the SAV ratio of the material.
As reported previously, control of the beads can be directed to some extent by the aliphatic:aqueous ratios in the emulsion. However, we have reported recently that addition of platinum(IV) chloride (PtCl4) inverts the porosity: materials are formed in which the PDMS is riddled with concave pores14. This indicates that the aqueous layer cavitates inside the aliphatic one, despite having similar aliphatic:aqueous ratios to those published in the original work13. The primary advantage of our method is that this concave porosity should naturally result in an increased SAV ratio, and thus, improved efficiency for analytical chemistry applications. While we are continuing to explore the specific effects of the addition of the platinum compound, we show here that the same effect can be accomplished using any aqueously soluble ionic compound, though perhaps to a reduced extent. Because our techniques also differ in some key aspects from what has been previously reported, we present our protocols here as a video to encourage others to extend our methods. Most notably, we use a common bath sonicator of the type used to clean glassware or other equipment, rather than the (considerably more expensive) probe sonicator often used in microbubble fabrication. This adjusted approach to the microbubble fabrication procedure could potentially be extended for the production of large quantities of bulk materials as well, creating porous sheets or slabs which could have applications for biomedical devices, aerospace and automotive industry, or substrates for chemical catalysis. Users seeking to generate high-SAV-ratio, microstructured materials using other similar polymers for such analyses may find that our protocols can be extended to any polymer for which the microbubble emulsion technique can be applied.

<table><tbody><tr><td>Poly(dimethylsiloxane), vinyl terminated</td><td>Sigma-Aldrich</td><td>68083-19-2</td><td></td></tr><tr><td>n-Heptane</td><td>Sigma-Aldrich</td><td>142-82-5</td><td>Flammable</td></tr><tr><td>Triethoxysilane</td><td>Sigma-Aldrich</td><td>998-30-1</td><td>Flammable, Accutely Toxic</td></tr><tr><td>Sorbitan Monoleate (Span-80)</td><td>Fluker</td><td>1338-43-8</td><td></td></tr><tr><td>Platinum(IV) Chloride</td><td>Sigma-Aldrich</td><td>13454-96-1</td><td>Accutely Toxic</td></tr><tr><td>Zinc(II) Chloride</td><td>Sigma-Aldrich</td><td>7646-85-7</td><td></td></tr><tr><td>Sodium Chloride</td><td>Sigma-Aldrich</td><td>7647-14-5</td><td></td></tr><tr><td>2.8 L Water Bath Sonicator</td><td>VWR</td><td>97043-964</td><td></td></tr></tbody></table>

microbubble fabrication of concave-porosity pdms beads

Microbubble fabrication (by use of a fine emulsion) provides a means of increasing the surface-area-to-volume (SAV) ratio of polymer materials, which is particularly useful for separations applications. Porous polydimethylsiloxane (PDMS) beads can be produced by heat-curing such an emulsion, allowing the interface between the aqueous and aliphatic phases to mold the morphology of the polymer. In the procedures described here, both polymer and crosslinker (triethoxysilane) are sonicated together in a cold-bath sonicator. Following a period of cross-linking, emulsions are added dropwise to a hot surfactant solution, allowing the aqueous phase of the emulsion to separate, and forming porous polymer beads. We demonstrate that this method can be tuned, and the SAV ratio optimized, by adjusting the electrolyte content of the aqueous phase in the emulsion. Beads produced in this way are imaged with scanning electron microscopy, and representative SAV ratios are determined using Brunauer&#8211;Emmett&#8211;Teller (BET) analysis. Considerable variability with the electrolyte identity is observed, but the general trend is consistent: there is a maximum in SAV obtained at a specific concentration, after which porosity decreases markedly.

Farklı elektrolit koşulları emülsiyonlardan oluşan boncukların Örnek SEM görüntüleri, Şekil 1 &#39;de gösterilmiştir. Şekil 1A DUFAUD ile elde edilenler, ve ark., 13 benzer bir boncuk gösterir, herhangi bir elektrolit ilavesi olmadan, prosedürler kullanılarak üretilmiş. Boncuk her metal iyonu için farklı morfolojileri sonuçlanan Şekil 1B-D gösterilen. Gösterilen tüm görüntüler için, 0,03-M elektrolit çözeltileri 300 ul bu faz içinde 0.012 M bir elektrolit konsantrasyonu veren, sulu bir faz için DI suyun 300 ul yerine kullanılmıştır. Yüksek çözünürlüklü görüntüleri (a) elektrolit ve ZnCİ2 üretilen boncuk Şekil 2&#39;de gösterilmiştir. Brunauer-Emmett-Teller boncuk 16,17 beş farklı basınçlarda azot izotermleri kullanılarak gerçekleştirilmiştir (BET) analizi. Şekil 1 &#39;de gösterilen boncuklar t edildi<html> her bir durumda, BET analizi için kullanılan malzemelerin, aynı partiden Aken. BET analizi Tablo 1 &#39;de listelenen hacim oranı, yüzey alanı için niceliksel değerleri elde edilir. <img alt="figür 1" src="/files/ftp_upload/53440/53440fig1.jpg" /> Tüm boncuk Şekil 1. SEM Görüntüleri. Burada anlatılan mikrokabarcık imalat tekniği ile üretilen PDMS boncuk SEM görüntüleri. Sulu tabakanın (A) herhangi bir elektrolit ilavesi olmaksızın üretilmiş Boncuk özel dışbükey porozite bulunmaktadır. Tüm fotoğraflar için uzunluk ölçekleri figürü üzerinde ölçek çubuğu tarafından verilmektedir. Daire içine belirtildiği gibi PTCL 4 (B), ZnCl2 (C), ve NaCl (D) 0,012 M metal konsantrasyonunun net konsantrasyonu ile imal olanlar, mikro-kabarcık oluşumu nedeniyle içbükey gözeneklerin büyük ek dahil olmak üzere farklı morfolojiler göstermek alanı.les / ftp_upload / 53440 / 53440fig1large.jpg &quot;target =&quot; _ blank &quot;&gt; bu rakamın büyük halini görmek için lütfen buraya tıklayınız. <img alt="Şekil 2," src="/files/ftp_upload/53440/53440fig2.jpg" /> Şekil 2. Ayrıntılı SEM Görüntüleri. ZnCİ2 ile Closer SEM elektrolit eklenmiş olmadan üretilmiş (A) boncuk görüntüleri ve (B). Elektrolit ilavesi olmadan, küresel altyapılar genellikle daha büyük ve daha yakın bir yüzey alanı-hacim oranının artışına önemli ölçüde katkıda bulunmaktadır ZnCI2, ilavesiyle daha ambalajlanmıştır. Tüm fotoğraflar için uzunluk ölçekleri figürü üzerinde ölçek çubuğu tarafından verilmektedir. <a href="https://www.jove.com/files/ftp_upload/53440/53440fig2large.jpg" target="_blank">Bu rakamın büyük halini görmek için lütfen buraya tıklayınız.</a> <table border="0"><tbody><tr><td> Tuz eklendi </td><td> BET SAV Oranı (cm 2 / cm 3) </strong&gt; </td><td> SAV İyileştirme (bağıl kontrol etmek için) </td></tr><tr><td> Yoktur (kontrol) </td><td> 361,6 </td><td> 1 </td></tr><tr><td> PTCL 4 </td><td> 1849 </td><td> 5.1 </td></tr><tr><td> ZnCl2 </td><td> 11.060 </td><td> 30.6 </td></tr><tr><td> NaCl </td><td> 298,9 </td><td> 0.83 </td></tr></tbody></table> Tablo 1. BET analizi. Yüzey alanı-hacim malzemelerin Brunauer-Emmett-Teller (BET) izoterm analizi ile belirlenmiştir (SAV) oranları, değişik elektrolitlerin 0,012-M sulu çözeltiler, sulu fazlar üretilmiştir. Birinci kolon Şekil 1 de harfleri gelen resim panelini göstermektedir. SAV oranları birim kütlesi başına toplam yüzey alanı, numune kütlesinin ve örneğin toplam soğuk boş alan dayanmaktadır.

Watch this Scientific Journal Video about Microbubble Fabrication of Concave-porosity PDMS Beads at JoVE.com

Microbubble Fabrication of Concave-porosity PDMS Beads

Procedures used to generate microstructured concave-porosity polydimethylsiloxane beads are presented. Effects of electrolyte concentration and identity within the aqueous phase are particularly emphasized.

Konkav-gözenek PDMS Boncuk mikro-Fabrikasyon

Microbubble fabrication (by use of a fine emulsion) provides a means of increasing the surface-area-to-volume (SAV) ratio of polymer materials, which is ...

microbubble-fabrication-of-concave-porosity-pdms-beads

Nanyang Technological University

Research

JoVE Journal

Chemistry

8.3K Görüntüleme.  Western Kentucky University. Procedures used to generate microstructured concave-porosity polydimethylsiloxane beads are presented. Effects of electrolyte concentration and identity within the aqueous phase are particularly emphasized. 

Video: Microbubble Fabrication of Concave-porosity PDMS Beads

Micropunching Lithography for Generating Micro- and Submicron-patterns on Polymer Substrates

Conducting polymers have attracted great attention since the discovery of high conductivity in doped polyacetylene in 19771. They offer the advantages of low weight, easy tailoring of properties and a wide spectrum of applications2,3. Due to sensitivity of conducting polymers to environmental conditions (e.g., air, oxygen, moisture, high temperature and chemical solutions), lithographic techniques present significant technical challenges when working with these materials4. For example, current photolithographic methods, such as ultra-violet (UV), are unsuitable for patterning the conducting polymers due to the involvement of wet and/or dry etching processes in these methods. In addition, current micro/nanosystems mainly have a planar form5,6. One layer of structures is built on the top surfaces of another layer of fabricated features. Multiple layers of these structures are stacked together to form numerous devices on a common substrate. The sidewall surfaces of the microstructures have not been used in constructing devices. On the other hand, sidewall patterns could be used, for example, to build 3-D circuits, modify fluidic channels and direct horizontal growth of nanowires and nanotubes.
A macropunching method has been applied in the manufacturing industry to create macropatterns in a sheet metal for over a hundred years. Motivated by this approach, we have developed a micropunching lithography method (MPL) to overcome the obstacles of patterning conducting polymers and generating sidewall patterns. Like the macropunching method, the MPL also includes two operations (Fig. 1): (i) cutting; and (ii) drawing. The "cutting" operation was applied to pattern three conducting polymers4, polypyrrole (PPy), Poly(3,4-ethylenedioxythiophen)-poly(4-styrenesulphonate) (PEDOT) and polyaniline (PANI). It was also employed to create Al microstructures7. The fabricated microstructures of conducting polymers have been used as humidity8, chemical8, and glucose sensors9. Combined microstructures of Al and conducting polymers have been employed to fabricate capacitors and various heterojunctions9,10,11. The "cutting" operation was also applied to generate submicron-patterns, such as 100- and 500-nm-wide PPy lines as well as 100-nm-wide Au wires. The "drawing" operation was employed for two applications: (i) produce Au sidewall patterns on high density polyethylene (HDPE) channels which could be used for building 3D microsystems12,13,14, and (ii) fabricate polydimethylsiloxane (PDMS) micropillars on HDPE substrates to increase the contact angle of the channel15.

A micropunching lithography approach is developed to generate micro- and submicron-patterns on top, sidewall and bottom surfaces of polymer substrates. It overcomes the obstacles of patterning conducting polymers and generating sidewall patterns. This method allows rapid fabrication of multiple features and is free of aggressive chemistry.

Mikro ve mikron altı-desen Polimer yüzeyler üzerine oluşturuluyor için Litografi Micropunching

Conducting polymers have attracted great attention since the discovery of high conductivity in doped polyacetylene in 19771. They offer the advantages of ...

Mühendislik

Fabrication of a Microfluidic Device for the Compartmentalization of Neuron Soma and Axons

In this video, we demonstrate the technique of soft lithography with polydimethyl siloxane (PDMS) which we use to fabricate a microfluidic device for culturing neurons. Previously, a silicon wafer was patterned with the design for the neuron microfluidic device using SU-8 and photolithography to create a master mold, or what we simply refer to as a "master". Next, we pour the silicon polymer PDMS on top of the master which is then cured by heating the PDMS to 80&deg;C for 1 hour. The PDMS forms a negative mold of the device. The PDMS is then carefully cut and lifted away from the master. Holes are punched where the reservoirs will be and the excess PDMS trimmed away from the device. Nitrogen is used to blow away any excess debris from the device. At this point the devices are now ready for use and can either bonded to corning No. 1 cover glass with a plasma sterilizer/cleaner or can be reversibly bound to the cover glass by simply placing the device on top of the cover glass. The reversible bonding of the device to glass is covered in a separate video and requires first that the device be sterilized either with 70% ethanol or by autoclaving. Plasma treating sterilizes the devices so no further treatment is necessary. It is, however, important, when plasma-treating the devices, to add liquid to the devices within 10 minutes of the plasma treatment while the surfaces are still hydrophilic. Waiting longer than 10 minutes to add liquid to the device makes it difficult for the liquid to enter the device. The neuron devices are typically plasma-bound to cover glass and 0.5 mg/ml poly-L-lysine (PLL) in pH 8.5 borate buffer is immediately added to the device. After a minimum of 3 hours incubating with PLL, the devices are washed with dH2O water a minimum of 3 times with at least 15 minutes between each wash. Next, the water is removed and fresh media is added to the device. At this point the device is ready for use. It is important to remember at this point to never remove all the media from the device. Always leave media in the main channel.

In this video we demonstrate the technique of soft lithography with polydimethyl siloxane (PDMS) which we use to farbricate a microfluidic device for culturing neurons.

Nöron Soma ve Aksonlar compartmentalization mikroakışkan Aygıt Fabrikasyon

In this video, we demonstrate the technique of soft lithography with polydimethyl siloxane (PDMS) which we use to fabricate a microfluidic device for ...

Biyoloji

Microfluidic Chips Controlled with Elastomeric Microvalve Arrays

Miniaturized microfluidic systems provide simple and effective solutions for low-cost point-of-care diagnostics and high-throughput biomedical assays. Robust flow control and precise fluidic volumes are two critical requirements for these applications. We have developed microfluidic chips featuring elastomeric polydimethylsiloxane (PDMS) microvalve arrays that: 1) need no extra energy source to close the fluidic path, hence the loaded device is highly portable; and 2) allow for microfabricating deep (up to 1 mm) channels with vertical sidewalls and resulting in very precise features.

The PDMS microvalves-based devices consist of three layers: a fluidic layer containing fluidic paths and microchambers of various sizes, a control layer containing the microchannels necessary to actuate the fluidic path with microvalves, and a middle thin PDMS membrane that is bound to the control layer. Fluidic layer and control layers are made by replica molding of PDMS from SU-8 photoresist masters, and the thin PDMS membrane is made by spinning PDMS at specified heights. The control layer is bonded to the thin PDMS membrane after oxygen activation of both, and then assembled with the fluidic layer. The microvalves are closed at rest and can be opened by applying negative pressure (e.g., house vacuum). Microvalve closure and opening are automated via solenoid valves controlled by computer software.

Here, we demonstrate two microvalve-based microfluidic chips for two different applications. The first chip allows for storing and mixing precise sub-nanoliter volumes of aqueous solutions at various mixing ratios. The second chip allows for computer-controlled perfusion of microfluidic cell cultures.

The devices are easy to fabricate and simple to control. Due to the biocompatibility of PDMS, these microchips could have broad applications in miniaturized diagnostic assays as well as basic cell biology studies.

We demonstrate protocols for manufacturing and automating elastomeric polydimethylsiloxane (PDMS)-based microvalve arrays that need no extra energy to close and feature photolithographically defined precise volumes. A parallel subnanoliter-volume mixer and an integrated microfluidic perfusion system are presented.

Elastomerik Mikrovalf Diziler Kontrollü mikroakışkan Chips

Miniaturized microfluidic systems provide simple and effective solutions for low-cost point-of-care diagnostics and high-throughput biomedical assays.  ...

High Throughput Single-cell and Multiple-cell Micro-encapsulation

Microfluidic encapsulation methods have been previously utilized to capture cells in picoliter-scale aqueous, monodisperse drops, providing confinement from a bulk fluid environment with applications in high throughput screening, cytometry, and mass spectrometry. We describe a method to not only encapsulate single cells, but to repeatedly capture a set number of cells (here we demonstrate one- and two-cell encapsulation) to study both isolation and the interactions between cells in groups of controlled sizes. By combining drop generation techniques with cell and particle ordering, we demonstrate controlled encapsulation of cell-sized particles for efficient, continuous encapsulation. Using an aqueous particle suspension and immiscible fluorocarbon oil, we generate aqueous drops in oil with a flow focusing nozzle. The aqueous flow rate is sufficiently high to create ordering of particles which reach the nozzle at integer multiple frequencies of the drop generation frequency, encapsulating a controlled number of cells in each drop. For representative results, 9.9 &mu;m polystyrene particles are used as cell surrogates. This study shows a single-particle encapsulation efficiency Pk=1 of 83.7% and a double-particle encapsulation efficiency Pk=2 of 79.5% as compared to their respective Poisson efficiencies of 39.3% and 33.3%, respectively. The effect of consistent cell and particle concentration is demonstrated to be of major importance for efficient encapsulation, and dripping to jetting transitions are also addressed. 
Introduction 
Continuous media aqueous cell suspensions share a common fluid environment which allows cells to interact in parallel and also homogenizes the effects of specific cells in measurements from the media. High-throughput encapsulation of cells into picoliter-scale drops confines the samples to protect drops from cross-contamination, enable a measure of cellular diversity within samples, prevent dilution of reagents and expressed biomarkers, and amplify signals from bioreactor products. Drops also provide the ability to re-merge drops into larger aqueous samples or with other drops for intercellular signaling studies.1,2 The reduction in dilution implies stronger detection signals for higher accuracy measurements as well as the ability to reduce potentially costly sample and reagent volumes.3 Encapsulation of cells in drops has been utilized to improve detection of protein expression,4 antibodies,5,6 enzymes,7 and metabolic activity8 for high throughput screening, and could be used to improve high throughput cytometry.9 Additional studies present applications in bio-electrospraying of cell containing drops for mass spectrometry10 and targeted surface cell coatings.11 Some applications, however, have been limited by the lack of ability to control the number of cells encapsulated in drops. Here we present a method of ordered encapsulation12 which increases the demonstrated encapsulation efficiencies for one and two cells and may be extrapolated for encapsulation of a larger number of cells.
To achieve monodisperse drop generation, microfluidic "flow focusing" enables the creation of controllable-size drops of one fluid (an aqueous cell mixture) within another (a continuous oil phase) by using a nozzle at which the streams converge.13 For a given nozzle geometry, the drop generation frequency f and drop size can be altered by adjusting oil and aqueous flow rates Qoil and Qaq. As the flow rates increase, the flows may transition from drop generation to unstable jetting of aqueous fluid from the nozzle.14 
When the aqueous solution contains suspended particles, particles become encapsulated and isolated from one another at the nozzle. For drop generation using a randomly distributed aqueous cell suspension, the average fraction of drops Dk containing k cells is dictated by Poisson statistics, where Dk = &lambda;k exp(-&lambda;)/(k!) and &lambda; is the average number of cells per drop. The fraction of cells which end up in the "correctly" encapsulated drops is calculated using Pk = (k x Dk)/&Sigma;(k' x Dk'). The subtle difference between the two metrics is that Dk relates to the utilization of aqueous fluid and the amount of drop sorting that must be completed following encapsulation, and Pk relates to the utilization of the cell sample. As an example, one could use a dilute cell suspension (low &lambda;) to encapsulate drops where most drops containing cells would contain just one cell. While the efficiency metric Pk would be high, the majority of drops would be empty (low Dk), thus requiring a sorting mechanism to remove empty drops, also reducing throughput.15
Combining drop generation with inertial ordering provides the ability to encapsulate drops with more predictable numbers of cells per drop and higher throughputs than random encapsulation. Inertial focusing was first discovered by Segre and Silberberg16 and refers to the tendency of finite-sized particles to migrate to lateral equilibrium positions in channel flow. Inertial ordering refers to the tendency of the particles and cells to passively organize into equally spaced, staggered, constant velocity trains. Both focusing and ordering require sufficiently high flow rates (high Reynolds number) and particle sizes (high Particle Reynolds number).17,18 Here, the Reynolds number Re =uDh/&nu; and particle Reynolds number Rep =Re(a/Dh)2, where u is a characteristic flow velocity, Dh [=2wh/(w+h)] is the hydraulic diameter, &nu; is the kinematic viscosity, a is the particle diameter, w is the channel width, and h is the channel height. Empirically, the length required to achieve fully ordered trains decreases as Re and Rep increase. Note that the high Re and Rep requirements (for this study on the order of 5 and 0.5, respectively) may conflict with the need to keep aqueous flow rates low to avoid jetting at the drop generation nozzle. Additionally, high flow rates lead to higher shear stresses on cells, which are not addressed in this protocol. The previous ordered encapsulation study demonstrated that over 90% of singly encapsulated HL60 cells under similar flow conditions to those in this study maintained cell membrane integrity.12 However, the effect of the magnitude and time scales of shear stresses will need to be carefully considered when extrapolating to different cell types and flow parameters. The overlapping of the cell ordering, drop generation, and cell viability aqueous flow rate constraints provides an ideal operational regime for controlled encapsulation of single and multiple cells.
Because very few studies address inter-particle train spacing,19,20 determining the spacing is most easily done empirically and will depend on channel geometry, flow rate, particle size, and particle concentration. Nonetheless, the equal lateral spacing between trains implies that cells arrive at predictable, consistent time intervals. When drop generation occurs at the same rate at which ordered cells arrive at the nozzle, the cells become encapsulated within the drop in a controlled manner. This technique has been utilized to encapsulate single cells with throughputs on the order of 15 kHz,12 a significant improvement over previous studies reporting encapsulation rates on the order of 60-160 Hz.4,15 In the controlled encapsulation work, over 80% of drops contained one and only one cell, a significant efficiency improvement over Poisson (random) statistics, which predicts less than 40% efficiency on average.12
In previous controlled encapsulation work,12 the average number of particles per drop &lambda; was tuned to provide single-cell encapsulation. We hypothesize that through tuning of flow rates, we can efficiently encapsulate any number of cells per drop when &lambda; is equal or close to the number of desired cells per drop. While single-cell encapsulation is valuable in determining individual cell responses from stimuli, multiple-cell encapsulation provides information relating to the interaction of controlled numbers and types of cells. Here we present a protocol, representative results using polystyrene microspheres, and discussion for controlled encapsulation of multiple cells using a passive inertial ordering channel and drop generation nozzle.

Combining monodisperse drop generation with inertial ordering of cells and particles, we describe a method to encapsulate a desired number of cells or particles in a single drop at kHz rates. We demonstrate efficiencies twice exceeding those of unordered encapsulation for single- and double-particle drops.

Yüksek Verim Micro-encapsulation Tek hücreli ve Çoklu-hücre

Microfluidic encapsulation methods have been previously utilized to capture cells in picoliter-scale aqueous, monodisperse drops, providing confinement ...

Biyomühendislik

Creating Sub-50 Nm Nanofluidic Junctions in PDMS Microfluidic Chip via Self-Assembly Process of Colloidal Particles

Polydimethylsiloxane (PDMS) is the prevailing building material to make microfluidic devices due to its ease of molding and bonding as well as its transparency. Due to the softness of the PDMS material, however, it is challenging to use PDMS for building nanochannels. The channels tend to collapse easily during plasma bonding. In this paper, we present an evaporation-driven self-assembly method of silica colloidal nanoparticles to create nanofluidic junctions with sub-50 nm pores between two microchannels. The pore size as well as the surface charge of the nanofluidic junction is tunable simply by changing the colloidal silica bead size and surface functionalization outside of the assembled microfluidic device in a vial before the self-assembly process. Using the self-assembly of nanoparticles with a bead size of 300 nm, 500 nm, and 900 nm, it was possible to fabricate a porous membrane with a pore size of ~45 nm, ~75 nm and ~135 nm, respectively. Under electrical potential, this nanoporous membrane initiated ion concentration polarization (ICP) acting as a cation-selective membrane to concentrate DNA by ~1,700 times within 15 min. This non-lithographic nanofabrication process opens up a new opportunity to build a tunable nanofluidic junction for the study of nanoscale transport processes of ions and molecules inside a PDMS microfluidic chip.

We propose a simple self-assembly technique of silica colloidal nanoparticles to create a nanofluidic junction between two microchannels in polydimethylsiloxane (PDMS). Using this technique, a nanoporous bead membrane with a pore size down to ~45 nm was built inside a microchannel and applied to electrokinetic preconcentration of DNA samples.

Kolloidal Parçacıkların Öz-Montaj Süreci yoluyla PDMS mikroakışkan Chip Sub-50 Nm Nanofluidic Junctions oluşturma

Polydimethylsiloxane (PDMS) is the prevailing building material to make microfluidic devices due to its ease of molding and bonding as well as its ...

A Microfluidic Technique to Probe Cell Deformability

Here we detail the design, fabrication, and use of a microfluidic device to evaluate the deformability of a large number of individual cells in an efficient manner. Typically, data for ~102 cells can be acquired within a 1 hr experiment. An automated image analysis program enables efficient post-experiment analysis of image data, enabling processing to be complete within a few hours. Our device geometry is unique in that cells must deform through a series of micron-scale constrictions, thereby enabling the initial deformation and time-dependent relaxation of individual cells to be assayed. The applicability of this method to human promyelocytic leukemia (HL-60) cells is demonstrated. Driving cells to deform through micron-scale constrictions using pressure-driven flow, we observe that human promyelocytic (HL-60) cells momentarily occlude the first constriction for a median time of 9.3 msec before passaging more quickly through the subsequent constrictions with a median transit time of 4.0 msec per constriction. By contrast, all-trans retinoic acid-treated (neutrophil-type) HL-60 cells occlude the first constriction for only 4.3 msec before passaging through the subsequent constrictions with a median transit time of 3.3 msec. This method can provide insight into the viscoelastic nature of cells, and ultimately reveal the molecular origins of this behavior.

We demonstrate a microfluidics-based assay to measure the timescale for cells to transit through a sequence of micron-scale constrictions.

Mikroakışkan Tekniği Hücre deformabilitesi Probe

Here we detail the design, fabrication, and use of a microfluidic device to evaluate the deformability of a large number of individual cells in an ...

Fabrication of Refractive-index-matched Devices for Biomedical Microfluidics

The use of microfluidic devices has emerged as a defining tool for biomedical applications. When combined with modern microscopy techniques, these devices can be implemented as part of a robust platform capable of making simultaneous complementary measurements. The primary challenge created by the combination of these two techniques is the mismatch in refractive index between the materials traditionally used to make microfluidic devices and the aqueous solutions typically used in biomedicine. This mismatch can create optical artifacts near the channel or device edges. One solution is to reduce the refractive index of the material used to fabricate the device by using a fluorinated polymer such as MY133-V2000 whose refractive index is similar to that of water (n = 1.33). Here, the construction of a microfluidic device made out of MY133-V2000 using soft lithography techniques is demonstrated, using O2 plasma in conjunction with an acrylic holder to increase the adhesion between the MY133-V2000 fabricated device and the polydimethylsiloxane (PDMS) substrate. The device is then tested by incubating it filled with cell culture media for 24 h to demonstrate the ability of the device to maintain cell culture conditions during the course of a typical imaging experiment. Finally, quantitative phase microscopy (QPM) is used to measure the distribution of mass within the live adherent cells in the microchannel. This way, the increased precision, enabled by fabricating the device from a low index of refraction polymer such as MY133-V2000 in lieu of traditional soft lithography materials such as PDMS, is demonstrated. Overall, this approach for fabricating microfluidic devices can be readily integrated into existing soft lithography workflows in order to reduce optical artifacts and increase measurement precision.

This protocol describes the fabrication of microfluidic devices from MY133-V2000 to eliminate artifacts that often arise in microchannels due to the mismatching refractive indices between microchannel structures and an aqueous solution. This protocol uses an acrylic holder to compress the encapsulated device, improving adhesion both chemically and mechanically.

Biyomedikal Havacilik için refraktif Dizin eşleşen cihazların imalat

The use of microfluidic devices has emerged as a defining tool for biomedical applications. When combined with modern microscopy techniques, these devices ...

Double Emulsion Generation Using a Polydimethylsiloxane (PDMS) Co-axial Flow Focus Device

Double emulsions are useful in a number of biological and industrial applications in which it is important to have an aqueous carrier fluid. This paper presents a polydimethylsiloxane (PDMS) microfluidic device capable of generating water/oil/water double emulsions using a coaxial flow focusing geometry that can be fabricated entirely using soft lithography. Similar to emulsion devices using glass capillaries, double emulsions can be formed in channels with uniform wettability and with dimensions much smaller than the channel sizes. Three dimensional flow focusing geometry is achieved by casting a pair of PDMS slabs using two layer soft lithography, then mating the slabs together in a clamshell configuration. Complementary locking features molded into the PDMS slabs enable the accurate registration of features on each of the slab surfaces. Device testing demonstrates formation of double emulsions from 14 &#181;m to 50 &#181;m in diameter while using large channels that are robust against fouling and clogging.

Double Emulsion Generation Using a Polydimethylsiloxane PDMS Co-axial Flow Focus Device

Microfluidic double emulsions generation typically involves devices with patterned wettability or custom-fabricated glass components. Here we describe the fabrication and testing of an all polydimethylsiloxane (PDMS) double emulsion generator that does not require surface treatment or complicated fabrication processes, and is capable of producing double emulsions down to 14 &#181;m.

Bir Polidimetilsiloksan (PDMS) Koaksiyel Akış Odak Aygıtı Kullanma Çift Emülsiyon Üretimi

Double emulsions are useful in a number of biological and industrial applications in which it is important to have an aqueous carrier fluid. This paper ...

Window on a Microworld: Simple Microfluidic Systems for Studying Microbial Transport in Porous Media

Microbial growth and transport in porous media have important implications for the quality of groundwater and surface water, the recycling of nutrients in the environment, as well as directly for the transmission of pathogens to drinking water supplies. Natural porous media is composed of an intricate physical topology, varied surface chemistries, dynamic gradients of nutrients and electron acceptors, and a patchy distribution of microbes. These features vary substantially over a length scale of microns, making the results of macro-scale investigations of microbial transport difficult to interpret, and the validation of mechanistic models challenging. Here we demonstrate how simple microfluidic devices can be used to visualize microbial interactions with micro-structured habitats, to identify key processes influencing the observed phenomena, and to systematically validate predictive models. Simple, easy-to-use flow cells were constructed out of the transparent, biocompatible and oxygen-permeable material poly(dimethyl siloxane). Standard methods of photolithography were used to make micro-structured masters, and replica molding was used to cast micro-structured flow cells from the masters. The physical design of the flow cell chamber is adaptable to the experimental requirements: microchannels can vary from simple linear connections to complex topologies with feature sizes as small as 2 &mu;m. Our modular EcoChip flow cell array features dozens of identical chambers and flow control by a gravity-driven flow module. We demonstrate that through use of EcoChip devices, physical structures and pressure heads can be held constant or varied systematically while the influence of surface chemistry, fluid properties, or the characteristics of the microbial population is investigated. Through transport experiments using a non-pathogenic, green fluorescent protein-expressing Vibrio bacterial strain, we illustrate the importance of habitat structure, flow conditions, and inoculums size on fundamental transport phenomena, and with real-time particle-scale observations, demonstrate that microfluidics offer a compelling view of a hidden world.

Microfluidic devices can be used to visualize complex natural processes in real time and at the appropriate physical scales. We have developed a simple microfluidic device that mimics key features of natural porous media for studying growth and transport of bacteria in the subsurface.

Gözenekli Ortam Mikrobiyal Ulaştırma incelenmesi için basit mikroakışkan Sistemleri: Mikrodünya Pencere

Microbial growth and transport in porous media have important implications for the quality of groundwater and surface water, the recycling of nutrients in ...

A Paired Bead and Magnet Array for Molding Microwells with Variable Concave Geometries

A spheroid culture is a useful tool for understanding cellular behavior in that it provides an in vivo-like three-dimensional environment. Various spheroid production methods such as non-adhesive surfaces, spinner flasks, hanging drops, and microwells have been used in studies of cell-to-cell interaction, immune-activation, drug screening, stem cell differentiation, and organoid generation. Among these methods, microwells with a three-dimensional concave geometry have gained the attention of scientists and engineers, given their advantages of uniform-sized spheroid generation and the ease with which the responses of individual spheroids can be monitored. Even though cost-effective methods such as the use of flexible membranes and ice lithography have been proposed, these techniques incur serious drawbacks such as difficulty in controlling the pattern sizes, achievement of high aspect ratios, and production of larger areas of microwells. To overcome these problems, we propose a robust method for fabricating concave microwells without the need for complex high-cost facilities. This method utilizes a 30 x 30 through-hole array, several hundred micrometer-order steel beads, and magnetic force to fabricate 900 microwells in a 3 cm x 3 cm polydimethylsiloxane (PDMS) substrate. To demonstrate the applicability of our method to cell biological applications, we cultured adipose stem cells for 3 days and successfully produced spheroids using our microwell platform. In addition, we performed a magnetostatic simulation to investigate the mechanism, whereby magnetic force was used to trap the steel beads in the through-holes. We believe that the proposed microwell fabrication method could be applied to many spheroid-based cellular studies such as drug screening, tissue regeneration, stem cell differentiation, and cancer metastasis.

This manuscript introduces a robust method of fabricating concave microwells without the need for complex high-cost facilities. Using magnetic force, steel beads, and a through-hole array, several hundred microwells were formed in a 3 cm x 3 cm polydimethylsiloxane (PDMS) substrate.