Contents lists available at ScienceDirect Microelectronic Engineering journal homepage: www.elsevier.com/locate/mee Research paper Strengthening of alumina tubular membrane by Al support and its application for oil-in-water stable emulsion M. Latif ⁎ , Ajab Khan Kasi, Jafar Khan Kasi, Muzamil Bokhari Department of Physics, University of Balochistan, Quetta 87300, Pakistan ARTICLE INFO Keywords: Robust alumina membrane Al mesh Al supported alumina tubular membrane Mechanical stability Nanoemulsion Flow rate ABSTRACT This research presents the fabrication of thinner and robust alumina tubular membrane for application in high pressure atmosphere. Thinner alumina tubular membrane systems were fabricated with Al mesh support to enhance its mechanical stability. The Al supported alumina tubular membrane (ASATM) and unsupported alumina tubular membrane (USATM) of different thicknesses were formed and their mechanical stability was measured. The ASATM of thickness 1.8 to 18 μm are able to tolerate pressure gradient from 6.4 to 450 kPa respectively. From mechanical stability analysis of both membrane systems having thicknesses 9 and 18 μm, it was found that breaking strength of ASATM is 31 to 43 fold higher than USATM. Both of the membrane systems were tested for permeation of sunflower oil. ASATM leads USATM in fluid flow due to lower possible thickness and tolerance of higher transmembrane pressure (TMP). The ASATM of 18 μm thickness was used for pre- paration of oil-in-water (O/W) emulsion. At optimized conditions the ASATM produces nano emulsion with 183 nm mean droplet size and span value 0.342. The emulsion was tested for 130 days and did not find any significant change in droplet size for 120 days. To the best of our literature review such a high stable emulsion is never reported before using any other type of membrane. The ASATM is much beneficial in terms of mechanical stability, flow rate, fabrication time, cost and applicability. 1. Introduction Anodic aluminum oxide (AAO) membrane is popular for its self- assembled, well-ordered, and controllable pore size [1–6]. The AAO is usually fabricated using mild anodization (MA) in which growth rate remains very low (2-6μmh -1 ). In 2006, Lee et. al, reported the fast fabrication of well-ordered AAO using hard anodization (HA) which is 25–35 times faster than MA [7]. The AAO has been used for different applications including, template assisted synthesis of nanostructures, fabrication of high density magnetic memories, sensors, optoelec- tronics, enzyme encapsulation, bio-filtration, gas separation, hemodia- lysis, and protein separation [8–18]. In particular applications such as filtration where high pressure gradient is involved, the mechanical stability becomes bottleneck for AAO membrane. Different parameters related to mechanical stability such as hardness, Young's modulus, and fracture toughness for AAO flat membranes have been observed ex- perimentally [19–23]. In thin flat AAO membranes the mechanical strength have been achieved using Al and Si support [24,25]. For fil- tration applications the anodic alumina flat membrane is difficult to integrate in fluidic modules. The USATM is a better option because it is easy to integrate to form a filtration module. The first USATM was prepared in 1996 by N. Itoh. et. al, accordingly Al tube was externally anodized while Al and barrier layer (BL) was etched chemically from inner side of tube [26]. Their fabrication steps were very complex in which tedious processing conditions were controlled in a narrow pro- cessing window. Later it was explored that membrane fabricated by external anodization of Al tube is mechanically unstable and most of the times cracks were observed [27]. For making strengthen alumina tub- ular membrane the N. Itoh et al., fabricated alumina membrane on the inner surface of Al tube [28,29]. The technique of internal anodization was also adopted by Belwalker, et al. in 2008 and Attaluri, et al., in 2009 [16,30]. Kasi et al. in 2012 introduced continues voltage de- tachment and etching (CVDE) process for producing pristine AAO tubular membrane [31]. The CVDE can never be used for having Al support in AAO tubular membrane for increasing its mechanical sta- bility. The main efforts in strengthening USATM were internal anodi- zation and increasing thickness of alumina tube. However increasing thickness of USATM hindered their usability for filtration applications. To the best of our knowledge, there is no report to reduce the tubular membrane thickness while increasing its mechanical stability for en- hancing its practicality in number of applications such as, filtration, nanoseparation and nanoemulsion. In application such as oil-in-water https://doi.org/10.1016/j.mee.2019.111134 Received 28 March 2019; Received in revised form 10 September 2019; Accepted 11 September 2019 ⁎ Corresponding author. E-mail address: latifphy@gmail.com (M. Latif). Microelectronic Engineering 218 (2019) 111134 Available online 12 September 2019 0167-9317/ © 2019 Elsevier B.V. All rights reserved. T