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Electrospinning water harvesters inspired by spider silk and beetle
Accepted Manuscript Electrospinning water harvesters inspired by spider silk and beetle Zhao-Xia Huang, Xiaoxiao Liu, Jiawei Wu, Shing-Chung Wong, Jin-Ping Qu PII: DOI: Reference:
S0167-577X(17)31407-6 https://doi.org/10.1016/j.matlet.2017.09.072 MLBLUE 23186
To appear in:
Materials Letters
Received Date: Revised Date: Accepted Date:
31 August 2017 18 September 2017 20 September 2017
Please cite this article as: Z-X. Huang, X. Liu, J. Wu, S-C. Wong, J-P. Qu, Electrospinning water harvesters inspired by spider silk and beetle, Materials Letters (2017), doi: https://doi.org/10.1016/j.matlet.2017.09.072
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Electrospinning water harvesters inspired by spider silk and beetle Zhao-Xia Huang1,2, Xiaoxiao Liu1, Jiawei Wu1, Shing-Chung Wong1,*, Jin-Ping Qu2,** 1
Department of Mechanical Engineering, The University of Akron, Akron, OH 44325-3903, USA 2
National Engineering Research Center of Novel Equipment for Polymer Processing, Key
Laboratory of Polymer Processing Engineering of the Ministry of Education, South China University of Technology, Guangzhou 510640, China * **
Correspondence to: Correspondence to:
Shing-Chung Wong; Jin-Ping Qu;
e-mail: [email protected] e-mail: [email protected]
Abstract: Fabricating a water harvester that exhibits desirable performance is an essential task to solve the fresh water scarcity issue. In this manuscript, we introduced a bio-inspired concept for a novel bead-on-string nanofiber with hydrophobicity/hydrophilicity simultaneously by electrospinning technique, that can be used as a high-performance water harvester. Scanning electron microscopy (SEM) and water contact angle measurement showed the bio-inspired structures of novel water harvesters and a custom-made setup was used to evaluate its water harvesting ability. The water harvesting efficiency of our membrane was determined to be 744 mg/cm2/h, which was 91% higher than the virgin PAN membrane. The durability was also tested and reported. Keywords: Water harvester; Electrospinning; Bio-inspired; Spider silk; Beetle Introduction Recently, artificial water harvesters have attracted much attention as a method to solve the growing global fresh water scarcity caused by desertification, climate change and global warming. Various materials were developed to achieve the best water harvesting performance as well as the simplest fabrication process.
1
Typically, water harvesting process can be divided into two steps: the first is to capture water droplets from fog, while the second is to condense the captured water droplets and peel-off [1]. During the first step, hydrophilic surfaces tend to show a higher capturing efficiency due to their low nucleation energy barrier [2]. However, this will stimulate the captured water droplets to spread on the surface rather than maintaining their spherical shapes, and it further obstructs the condensing and peel-off during water harvesting. In contrast, as discussed in our previous work [3], hydrophobic materials tend to gain higher efficiencies in the second step that benefits from their higher water contact angles and lower contact angle hysteresis. Due to the opposite mechanisms in these two steps, how to fabricate a water harvester that exhibits excellent performance in both capture and peel-off processes seems to be a pivotal task. In this manuscript, to address this issue, we introduce a novel concept to harvest water as inspired by spider silk and desert beetle. Polyacrylonitrile (PAN) and expanded graphite (EG) were used to form the bicomponent nanofibers. The bead-on-string structure and complex wettability were confirmed by scanning electron microscopy (SEM) and water contact angle (WCA) measurement. The water harvesting performance was evaluated by a custom-made setup. The durability was also tested and reported. Experimental section Materials PAN powders (Mw = 150,000) came from Sigma-Aldrich Corporation. Expandable graphite flakes (Grade 160-80 N) were from GrafTech International. N,N-dimethylformamide (DMF) was from Sigma-Aldrich Corporation and used as received. Preparation of bio-inspired membranes
2
EG was prepared as described in our previous report [3]. DMF was employed to dissolve PAN with polymer concentration kept at 10 wt%. NGP was then added to form the composite solution with PAN/EG weight ratio of 100/2. A virgin PAN solution was also prepared as reference. A standard electrospinning setup was used to fabricate the membranes (see Figure 1(A)). The solution was fed into a 5-ml syringe fitted with 21-gauge needle connected to high voltage. Aluminum foil collector was placed 20 cm away from the needle. Electrospinning was performed at voltage of 15-17 kV with flow rate of 1.5 mL/h till the basis weight of sample reached 15 g/m2. As-spun membranes were placed in oven at 70 °C overnight.
Figure 1. (A) Schematic of electrospinning setup; (B) Custom-made water harvesting evaluation setup.
Characterizations Morphologies were evaluated by a scanning electron microscope (SEM, JSM-6510LV, JEOL). WCA measurement was performed by a contact angle meter (DMS-200, Kyowa). Water harvesting ability evaluation A custom-made setup was used to determine the water harvesting abilities of as-spun membranes (see Figure 1(B)). As described in our previous work [3], a commercial humidifier was employed to supply the air stream. Sample with size of 4×4 cm2 was placed 5 cm away from
3
the nozzle of the humidifier. A vial was placed under the sample to collect the condensed water. Every test lasted for 1 h before it was weighed. For every sample, five repetitions were performed.
Results and discussions Owing to the unique bead-on-string silk, spiders could harvest water from fog. To show the spider silk-like structure, the morphologies of membranes with and without NGP inclusions were studied by SEM (see Figure 2 (A, B)). Randomly dispersed nanofibers can be determined in both samples. Bead-free nanofibers were detected in virgin PAN, which indicates proper processing we used. Bead-on-string structures are founded in sample with EG inclusions. As discussed in our previous work [3], the beads can be considered as the EG particles that locate on the PAN nanofibers randomly (EG beads are marked by red arrows). The bead-on-string structures of sample with EG inclusions show the formation of spider silk-like membranes.
Figure 2. (A and B) SEM micrographs of virgin PAN and composite membranes, respectively (EG beads are marked by red arrows); (C and D) fiber diameter distributions of virgin PAN and composite membranes, respectively.
4
The average fiber diameters were measured by ImageJ software, where 100-150 counts chosen from 3-5 SEM micrographs (shown in Figure 2 (C, D)). The mean diameter of virgin PAN fiber is determined to be around 591 nm. After the inclusion of EG, the diameter does not show obvious change. The results demonstrated the inclusion of EG has little influence on the diameters of as-spun nanofibers, which can be attributed to the EG-induced conductivity and viscosity of composite solution. Similar results were reported by Kaner and coworkers [4]. The essential feature of a desert beetle that ensures it to harvest water in a desert is containing both hydrophobic and hydrophilic parts in its back [5]. Herein, the wettability of asspun membranes, as well as EG particles, was evaluated. It needs to be pointed out that the EG sample was prepared by casting the EG/DMF solution on an aluminum foil, followed by evaporation overnight. During the measurement, both virgin PAN and composite membranes were rapidly wetted by water droplets (5 µL) and exhibited ultra-hydrophilicity [6]. The photograph of water droplets on EG surface is shown in Figure 3(A). Consequently, the WCA of EG is measured to be 107.9˚ and it demonstrates the hydrophobic nature of EG.
Figure 3. (A) Water droplets placed on EG surface; (B) WHE of virgin PAN and composite membrane; (C) WHE of composite membrane under different cycle.
Normally, water harvesting efficiency (WHE) is used to determine the performance of a water harvester and is defined as the weight of harvested water per unit area per hour. The WHE of composite membrane is determined to be 744 mg/cm2/h (see Figure 3(B)), indicating that our bio-inspired water harvester can collect 744 mg water per unit area per hour. As a reference, the 5
virgin PAN membrane exhibits a WHE value of 389 mg/cm2/h. An improvement of 91% in WHE is achieved in our experiment by inclusion of EG. In other words, the formation of beadon-string nanofibers with dual-wettability can enhance the water harvesting ability by 91%. Due to the spider silk and beetle like structure, the water harvesting mechanism of our membrane is in line with two parts - details are shown in SI. When moist airflow contacts the membrane, the PAN strings are easily wetted by the water droplets, which serve as the nucleation agents and capture water droplets due to their higher apparent surface energy and lower nucleation energy barrier as compared to EG beads. After water droplets are captured, two different forces will drive the water droplets transfer to the EG beads [7]. One of the forces is caused by wettability gradient between PAN and EG; moreover, investigators [8] found the transfer speed of droplets on such surface ranged from centimeter to meter per second. The other force is due to Laplace pressure gradient created by the bead-on-string morphology [9]. Thus, the collaborative effect of these two forces can ensure the water droplets transfer to EG beads at an extremely high speed. When transferred to EG surfaces, the water droplets can easily peel off from the surface due to the hydrophobicity of EG. Thus, high efficiencies in both capture and peel-off steps explain why such improvement in WHE can be achieved in our novel harvester. Due to the limited scope of the this paper, a direct observation of water harvesting process will await future studies. Recently, Yaghi and coworkers’ investigation in water harvesting area attracted attention [10]. Where a porous metal-organic framework (MOF) was fabricated and able to harvest 2.8kilogram water per square meter of MOF daily. In present work, the capacity of our bio-inspired water harvester can be converted to about 179-kilogram water per square meter per day. Moreover, the density of as-reported MOF was 1 kg/m2, while ours is only 15 g/m2. Although a
6
direct comparison cannot be made due to different experimental conditions, our membrane shows a better water harvesting ability than the MOF one. As a high-performance water harvester, durability is an essential property. Thus, a multicycle water harvesting experiment was conducted and the WHE values were recorded (see Figure 3(C)). From the result, it can be demonstrated that our composite membrane can maintain a high WHE level even after several cycles of test. Conclusion In this work, a novel water harvester which is inspired by both spider silk and desert beetle was fabricated by electrospinning process. Bead-on-string nanofibers were determined by SEM, where PAN and EG served as the string and bead parts, respectively. Due to different wettability of PAN and EG, we evidenced the formation of desert beetle-like structure. In the following step, we evaluated the water harvesting ability of our novel water harvester with a virgin PAN sample as a reference. The results indicated that the formation of unique bio-inspired structure can significantly enhance the performance by improving the water harvesting efficiency of composite membrane by 91%, compared with the virgin sample. The composite membrane showed a desirable WHE of 744 mg/cm2/h. Ultimately, the durability of our novel water harvester was also shown to be robust. Acknowledgement We would like to acknowledge the support of this fundamental research by the University of Akron. The Key Program of National Natural Science Foundation of China (Grant No. 51435005) provided support for one of us (ZXH), who would like to thank the China Scholarship Council for his stipend’s support, during his tenure at the University of Akron. References
7
[1] S. Zhang, J. Huang, Z. Chen, Y. Lai, Bioinspired special wettability surfaces: from fundamental research to water harvesting applications, Small (2016). [2] K.K. Varanasi, M. Hsu, N. Bhate, W. Yang, T. Deng, Spatial control in the heterogeneous nucleation of water, Applied Physics Letters 95(9) (2009) 094101. [3] Z.-X. Huang, X. Liu, S.-C. Wong, J.-p. Qu, Electrospinning polyvinylidene fluoride/expanded graphite composite membranes as high efficiency and reusable water harvester, Materials Letters 202 (2017) 78-81. [4] J.J. Mack, L.M. Viculis, A. Ali, R. Luoh, G. Yang, H.T. Hahn, F.K. Ko, R.B. Kaner, Graphite nanoplatelet reinforcement of electrospun polyacrylonitrile nanofibers, Advanced Materials 17(1) (2005) 77-80. [5] A.R. Parker, C.R. Lawrence, Water capture by a desert beetle, Nature 414(6859) (2001) 33. [6] J. Zhang, Q. Xue, X. Pan, Y. Jin, W. Lu, D. Ding, Q. Guo, Graphene oxide/polyacrylonitrile fiber hierarchical-structured membrane for ultra-fast microfiltration of oil-water emulsion, Chemical Engineering Journal 307 (2017) 643-649. [7] Y. Hou, Y. Chen, Y. Xue, Y. Zheng, L. Jiang, Water collection behavior and hanging ability of bioinspired fiber, Langmuir 28(10) (2012) 4737-4743. [8] S. Daniel, M.K. Chaudhury, J.C. Chen, Fast drop movements resulting from the phase change on a gradient surface, Science 291(5504) (2001) 633-636. [9] E. Lorenceau, D. Quere, Drops on a conical wire, Journal of Fluid Mechanics 510 (2004) 2945. [10] H. Kim, S. Yang, S.R. Rao, S. Narayanan, E.A. Kapustin, H. Furukawa, A.S. Umans, O.M. Yaghi, E.N. Wang, Water harvesting from air with metal-organic frameworks powered by natural sunlight, Science 356(6336) (2017) 430-434.
8
Highlights
•
Bio-inspired PAN/EG membrane has been fabricated by electrospinning technique.
•
Water harvesting efficiency shows 91% higher than control sample.
•
PAN/EG membrane shows durability in water harvesting.
9
S0167-577X(17)31407-6 https://doi.org/10.1016/j.matlet.2017.09.072 MLBLUE 23186
To appear in:
Materials Letters
Received Date: Revised Date: Accepted Date:
31 August 2017 18 September 2017 20 September 2017
Please cite this article as: Z-X. Huang, X. Liu, J. Wu, S-C. Wong, J-P. Qu, Electrospinning water harvesters inspired by spider silk and beetle, Materials Letters (2017), doi: https://doi.org/10.1016/j.matlet.2017.09.072
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Electrospinning water harvesters inspired by spider silk and beetle Zhao-Xia Huang1,2, Xiaoxiao Liu1, Jiawei Wu1, Shing-Chung Wong1,*, Jin-Ping Qu2,** 1
Department of Mechanical Engineering, The University of Akron, Akron, OH 44325-3903, USA 2
National Engineering Research Center of Novel Equipment for Polymer Processing, Key
Laboratory of Polymer Processing Engineering of the Ministry of Education, South China University of Technology, Guangzhou 510640, China * **
Correspondence to: Correspondence to:
Shing-Chung Wong; Jin-Ping Qu;
e-mail: [email protected] e-mail: [email protected]
Abstract: Fabricating a water harvester that exhibits desirable performance is an essential task to solve the fresh water scarcity issue. In this manuscript, we introduced a bio-inspired concept for a novel bead-on-string nanofiber with hydrophobicity/hydrophilicity simultaneously by electrospinning technique, that can be used as a high-performance water harvester. Scanning electron microscopy (SEM) and water contact angle measurement showed the bio-inspired structures of novel water harvesters and a custom-made setup was used to evaluate its water harvesting ability. The water harvesting efficiency of our membrane was determined to be 744 mg/cm2/h, which was 91% higher than the virgin PAN membrane. The durability was also tested and reported. Keywords: Water harvester; Electrospinning; Bio-inspired; Spider silk; Beetle Introduction Recently, artificial water harvesters have attracted much attention as a method to solve the growing global fresh water scarcity caused by desertification, climate change and global warming. Various materials were developed to achieve the best water harvesting performance as well as the simplest fabrication process.
1
Typically, water harvesting process can be divided into two steps: the first is to capture water droplets from fog, while the second is to condense the captured water droplets and peel-off [1]. During the first step, hydrophilic surfaces tend to show a higher capturing efficiency due to their low nucleation energy barrier [2]. However, this will stimulate the captured water droplets to spread on the surface rather than maintaining their spherical shapes, and it further obstructs the condensing and peel-off during water harvesting. In contrast, as discussed in our previous work [3], hydrophobic materials tend to gain higher efficiencies in the second step that benefits from their higher water contact angles and lower contact angle hysteresis. Due to the opposite mechanisms in these two steps, how to fabricate a water harvester that exhibits excellent performance in both capture and peel-off processes seems to be a pivotal task. In this manuscript, to address this issue, we introduce a novel concept to harvest water as inspired by spider silk and desert beetle. Polyacrylonitrile (PAN) and expanded graphite (EG) were used to form the bicomponent nanofibers. The bead-on-string structure and complex wettability were confirmed by scanning electron microscopy (SEM) and water contact angle (WCA) measurement. The water harvesting performance was evaluated by a custom-made setup. The durability was also tested and reported. Experimental section Materials PAN powders (Mw = 150,000) came from Sigma-Aldrich Corporation. Expandable graphite flakes (Grade 160-80 N) were from GrafTech International. N,N-dimethylformamide (DMF) was from Sigma-Aldrich Corporation and used as received. Preparation of bio-inspired membranes
2
EG was prepared as described in our previous report [3]. DMF was employed to dissolve PAN with polymer concentration kept at 10 wt%. NGP was then added to form the composite solution with PAN/EG weight ratio of 100/2. A virgin PAN solution was also prepared as reference. A standard electrospinning setup was used to fabricate the membranes (see Figure 1(A)). The solution was fed into a 5-ml syringe fitted with 21-gauge needle connected to high voltage. Aluminum foil collector was placed 20 cm away from the needle. Electrospinning was performed at voltage of 15-17 kV with flow rate of 1.5 mL/h till the basis weight of sample reached 15 g/m2. As-spun membranes were placed in oven at 70 °C overnight.
Figure 1. (A) Schematic of electrospinning setup; (B) Custom-made water harvesting evaluation setup.
Characterizations Morphologies were evaluated by a scanning electron microscope (SEM, JSM-6510LV, JEOL). WCA measurement was performed by a contact angle meter (DMS-200, Kyowa). Water harvesting ability evaluation A custom-made setup was used to determine the water harvesting abilities of as-spun membranes (see Figure 1(B)). As described in our previous work [3], a commercial humidifier was employed to supply the air stream. Sample with size of 4×4 cm2 was placed 5 cm away from
3
the nozzle of the humidifier. A vial was placed under the sample to collect the condensed water. Every test lasted for 1 h before it was weighed. For every sample, five repetitions were performed.
Results and discussions Owing to the unique bead-on-string silk, spiders could harvest water from fog. To show the spider silk-like structure, the morphologies of membranes with and without NGP inclusions were studied by SEM (see Figure 2 (A, B)). Randomly dispersed nanofibers can be determined in both samples. Bead-free nanofibers were detected in virgin PAN, which indicates proper processing we used. Bead-on-string structures are founded in sample with EG inclusions. As discussed in our previous work [3], the beads can be considered as the EG particles that locate on the PAN nanofibers randomly (EG beads are marked by red arrows). The bead-on-string structures of sample with EG inclusions show the formation of spider silk-like membranes.
Figure 2. (A and B) SEM micrographs of virgin PAN and composite membranes, respectively (EG beads are marked by red arrows); (C and D) fiber diameter distributions of virgin PAN and composite membranes, respectively.
4
The average fiber diameters were measured by ImageJ software, where 100-150 counts chosen from 3-5 SEM micrographs (shown in Figure 2 (C, D)). The mean diameter of virgin PAN fiber is determined to be around 591 nm. After the inclusion of EG, the diameter does not show obvious change. The results demonstrated the inclusion of EG has little influence on the diameters of as-spun nanofibers, which can be attributed to the EG-induced conductivity and viscosity of composite solution. Similar results were reported by Kaner and coworkers [4]. The essential feature of a desert beetle that ensures it to harvest water in a desert is containing both hydrophobic and hydrophilic parts in its back [5]. Herein, the wettability of asspun membranes, as well as EG particles, was evaluated. It needs to be pointed out that the EG sample was prepared by casting the EG/DMF solution on an aluminum foil, followed by evaporation overnight. During the measurement, both virgin PAN and composite membranes were rapidly wetted by water droplets (5 µL) and exhibited ultra-hydrophilicity [6]. The photograph of water droplets on EG surface is shown in Figure 3(A). Consequently, the WCA of EG is measured to be 107.9˚ and it demonstrates the hydrophobic nature of EG.
Figure 3. (A) Water droplets placed on EG surface; (B) WHE of virgin PAN and composite membrane; (C) WHE of composite membrane under different cycle.
Normally, water harvesting efficiency (WHE) is used to determine the performance of a water harvester and is defined as the weight of harvested water per unit area per hour. The WHE of composite membrane is determined to be 744 mg/cm2/h (see Figure 3(B)), indicating that our bio-inspired water harvester can collect 744 mg water per unit area per hour. As a reference, the 5
virgin PAN membrane exhibits a WHE value of 389 mg/cm2/h. An improvement of 91% in WHE is achieved in our experiment by inclusion of EG. In other words, the formation of beadon-string nanofibers with dual-wettability can enhance the water harvesting ability by 91%. Due to the spider silk and beetle like structure, the water harvesting mechanism of our membrane is in line with two parts - details are shown in SI. When moist airflow contacts the membrane, the PAN strings are easily wetted by the water droplets, which serve as the nucleation agents and capture water droplets due to their higher apparent surface energy and lower nucleation energy barrier as compared to EG beads. After water droplets are captured, two different forces will drive the water droplets transfer to the EG beads [7]. One of the forces is caused by wettability gradient between PAN and EG; moreover, investigators [8] found the transfer speed of droplets on such surface ranged from centimeter to meter per second. The other force is due to Laplace pressure gradient created by the bead-on-string morphology [9]. Thus, the collaborative effect of these two forces can ensure the water droplets transfer to EG beads at an extremely high speed. When transferred to EG surfaces, the water droplets can easily peel off from the surface due to the hydrophobicity of EG. Thus, high efficiencies in both capture and peel-off steps explain why such improvement in WHE can be achieved in our novel harvester. Due to the limited scope of the this paper, a direct observation of water harvesting process will await future studies. Recently, Yaghi and coworkers’ investigation in water harvesting area attracted attention [10]. Where a porous metal-organic framework (MOF) was fabricated and able to harvest 2.8kilogram water per square meter of MOF daily. In present work, the capacity of our bio-inspired water harvester can be converted to about 179-kilogram water per square meter per day. Moreover, the density of as-reported MOF was 1 kg/m2, while ours is only 15 g/m2. Although a
6
direct comparison cannot be made due to different experimental conditions, our membrane shows a better water harvesting ability than the MOF one. As a high-performance water harvester, durability is an essential property. Thus, a multicycle water harvesting experiment was conducted and the WHE values were recorded (see Figure 3(C)). From the result, it can be demonstrated that our composite membrane can maintain a high WHE level even after several cycles of test. Conclusion In this work, a novel water harvester which is inspired by both spider silk and desert beetle was fabricated by electrospinning process. Bead-on-string nanofibers were determined by SEM, where PAN and EG served as the string and bead parts, respectively. Due to different wettability of PAN and EG, we evidenced the formation of desert beetle-like structure. In the following step, we evaluated the water harvesting ability of our novel water harvester with a virgin PAN sample as a reference. The results indicated that the formation of unique bio-inspired structure can significantly enhance the performance by improving the water harvesting efficiency of composite membrane by 91%, compared with the virgin sample. The composite membrane showed a desirable WHE of 744 mg/cm2/h. Ultimately, the durability of our novel water harvester was also shown to be robust. Acknowledgement We would like to acknowledge the support of this fundamental research by the University of Akron. The Key Program of National Natural Science Foundation of China (Grant No. 51435005) provided support for one of us (ZXH), who would like to thank the China Scholarship Council for his stipend’s support, during his tenure at the University of Akron. References
7
[1] S. Zhang, J. Huang, Z. Chen, Y. Lai, Bioinspired special wettability surfaces: from fundamental research to water harvesting applications, Small (2016). [2] K.K. Varanasi, M. Hsu, N. Bhate, W. Yang, T. Deng, Spatial control in the heterogeneous nucleation of water, Applied Physics Letters 95(9) (2009) 094101. [3] Z.-X. Huang, X. Liu, S.-C. Wong, J.-p. Qu, Electrospinning polyvinylidene fluoride/expanded graphite composite membranes as high efficiency and reusable water harvester, Materials Letters 202 (2017) 78-81. [4] J.J. Mack, L.M. Viculis, A. Ali, R. Luoh, G. Yang, H.T. Hahn, F.K. Ko, R.B. Kaner, Graphite nanoplatelet reinforcement of electrospun polyacrylonitrile nanofibers, Advanced Materials 17(1) (2005) 77-80. [5] A.R. Parker, C.R. Lawrence, Water capture by a desert beetle, Nature 414(6859) (2001) 33. [6] J. Zhang, Q. Xue, X. Pan, Y. Jin, W. Lu, D. Ding, Q. Guo, Graphene oxide/polyacrylonitrile fiber hierarchical-structured membrane for ultra-fast microfiltration of oil-water emulsion, Chemical Engineering Journal 307 (2017) 643-649. [7] Y. Hou, Y. Chen, Y. Xue, Y. Zheng, L. Jiang, Water collection behavior and hanging ability of bioinspired fiber, Langmuir 28(10) (2012) 4737-4743. [8] S. Daniel, M.K. Chaudhury, J.C. Chen, Fast drop movements resulting from the phase change on a gradient surface, Science 291(5504) (2001) 633-636. [9] E. Lorenceau, D. Quere, Drops on a conical wire, Journal of Fluid Mechanics 510 (2004) 2945. [10] H. Kim, S. Yang, S.R. Rao, S. Narayanan, E.A. Kapustin, H. Furukawa, A.S. Umans, O.M. Yaghi, E.N. Wang, Water harvesting from air with metal-organic frameworks powered by natural sunlight, Science 356(6336) (2017) 430-434.
8
Highlights
•
Bio-inspired PAN/EG membrane has been fabricated by electrospinning technique.
•
Water harvesting efficiency shows 91% higher than control sample.
•
PAN/EG membrane shows durability in water harvesting.
9