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Smart gating membranes with in situ self-assembled responsive nanogels as functional gates.

Luo F, Xie R, Liu Z, Ju XJ, Wang W, Lin S, Chu LY - Sci Rep (2015)

Bottom Line: Smart gating membranes, inspired by the gating function of ion channels across cell membranes, are artificial membranes composed of non-responsive porous membrane substrates and responsive gates in the membrane pores that are able to dramatically regulate the trans-membrane transport of substances in response to environmental stimuli.Easy fabrication, high flux, significant response and strong mechanical strength are critical for the versatility of such smart gating membranes.The smart gating membranes with in situ self-assembled responsive nanogels as functional gates show large flux, significant response and excellent mechanical property simultaneously.

View Article: PubMed Central - PubMed

Affiliation: School of Chemical Engineering, Sichuan University, Chengdu, Sichuan 610065, China.

ABSTRACT
Smart gating membranes, inspired by the gating function of ion channels across cell membranes, are artificial membranes composed of non-responsive porous membrane substrates and responsive gates in the membrane pores that are able to dramatically regulate the trans-membrane transport of substances in response to environmental stimuli. Easy fabrication, high flux, significant response and strong mechanical strength are critical for the versatility of such smart gating membranes. Here we show a novel and simple strategy for one-step fabrication of smart gating membranes with three-dimensionally interconnected networks of functional gates, by self-assembling responsive nanogels on membrane pore surfaces in situ during a vapor-induced phase separation process for membrane formation. The smart gating membranes with in situ self-assembled responsive nanogels as functional gates show large flux, significant response and excellent mechanical property simultaneously. Because of the easy fabrication method as well as the concurrent enhancement of flux, response and mechanical property, the proposed smart gating membranes will expand the scope of membrane applications, and provide ever better performances in their applications.

No MeSH data available.


Related in: MedlinePlus

FESEM images of cross-section (a1–e1 and magnified a2–e2) and surface (a3–e3 and magnified a4–e4) views of membranes prepared via VIPS with different conditions.The nanogel content is 17%. (a) Exposure time is 2 min, vapor temperature is 25 °C, and relative humidity is 70%. (b) Exposure time is 2 min, vapor temperature is 15 °C, and relative humidity is 70%. (c) Exposure time is 2 min, vapor temperature is 25 °C, and relative humidity is 90%. (d) Exposure time is 20 min, vapor temperature is 25 °C, and relative humidity is 90%. (e) Exposure time is 20 min, vapor temperature is 15 °C, and relative humidity is 70%. Scale bars are 10 μm in (a1–e1) and (a3–e3), 1 μm in (a2–e2) and 3 μm in (a4–e4).
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f3: FESEM images of cross-section (a1–e1 and magnified a2–e2) and surface (a3–e3 and magnified a4–e4) views of membranes prepared via VIPS with different conditions.The nanogel content is 17%. (a) Exposure time is 2 min, vapor temperature is 25 °C, and relative humidity is 70%. (b) Exposure time is 2 min, vapor temperature is 15 °C, and relative humidity is 70%. (c) Exposure time is 2 min, vapor temperature is 25 °C, and relative humidity is 90%. (d) Exposure time is 20 min, vapor temperature is 25 °C, and relative humidity is 90%. (e) Exposure time is 20 min, vapor temperature is 15 °C, and relative humidity is 70%. Scale bars are 10 μm in (a1–e1) and (a3–e3), 1 μm in (a2–e2) and 3 μm in (a4–e4).

Mentions: In order to optimize the VIPS parameters for membrane preparation, we systematically investigate the effects of the exposure time, the relative humidity and the vapor temperature of VIPS chamber on the microstructure and performance of the membranes. The FESEM images of the membranes are shown in Fig. 3. The exposure process of casting solution in vapor is the primary difference between VIPS and LIPS; therefore, the exposure time should be very important for the membrane formation. Compared with the microstructure of the membrane prepared with exposure time of 20 min and vapor at 25 °C and 70% (RH) (Fig. 2f), that prepared with exposure time of 2 min and vapor at 25 °C and 70% (RH) is significantly different (Fig. 3a). When the exposure time is 20 min, the magnified FESEM micrographs clearly show that a lot of nanogels are observed on the pore/matrix interface and the surface (Fig. 2f2); however, when the exposure time is 2 min, only a few nanogels are observed on the pore/matrix interface and the surface (Fig. 3a2). This phenomenon gives an effective supplement to the formation of the gating structure. The liquid-liquid phase separation occurs in the membrane-forming solution induced by the water vapor, and then the droplets of the polymer-lean phases disperse in the continuous polymer-rich phases. The mild VIPS process gives enough time for the droplets to coarsen. At the same time, the nanogels tend to move to the matrix/growing phase interface due to its hydrophilic property. In this situation, 2 min may be enough for the formation of droplets of the polymer-lean phases, but cannot support the procedure of large number of nanogels moving to the pore/matrix interfaces. Then, we fix the exposure time at 2 min and adjust the vapor temperature to 15 °C and relative humidity to 90% (RH), separately. On the condition of exposure time of 2 min and vapor at 15 °C and 70% (RH), the membrane morphology turns to be finger-like, typical structure from LIPS (Fig. 3b1). The lower temperature slows down the phase separation process, which makes the droplets of the polymer-lean phases hard to coarsen and solidify. Meanwhile, few nanogels appear on the pore/matrix interfaces because the lower temperature slows down the moving velocity of the nanogels (Fig. 3b2). However, on the condition of exposure time of 2 min and vapor at 25 °C and 90% (RH), the membrane pores on the surface are enlarged (Fig. 3c3), which are in accordance with previously reported work27. The results show that the exposure time of 2 min is too short for the vapor to influence the membrane formation. Although the vapor temperature and relative humidity varies, the ideal membrane structures cannot be achieved with exposure time of 2 min.


Smart gating membranes with in situ self-assembled responsive nanogels as functional gates.

Luo F, Xie R, Liu Z, Ju XJ, Wang W, Lin S, Chu LY - Sci Rep (2015)

FESEM images of cross-section (a1–e1 and magnified a2–e2) and surface (a3–e3 and magnified a4–e4) views of membranes prepared via VIPS with different conditions.The nanogel content is 17%. (a) Exposure time is 2 min, vapor temperature is 25 °C, and relative humidity is 70%. (b) Exposure time is 2 min, vapor temperature is 15 °C, and relative humidity is 70%. (c) Exposure time is 2 min, vapor temperature is 25 °C, and relative humidity is 90%. (d) Exposure time is 20 min, vapor temperature is 25 °C, and relative humidity is 90%. (e) Exposure time is 20 min, vapor temperature is 15 °C, and relative humidity is 70%. Scale bars are 10 μm in (a1–e1) and (a3–e3), 1 μm in (a2–e2) and 3 μm in (a4–e4).
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f3: FESEM images of cross-section (a1–e1 and magnified a2–e2) and surface (a3–e3 and magnified a4–e4) views of membranes prepared via VIPS with different conditions.The nanogel content is 17%. (a) Exposure time is 2 min, vapor temperature is 25 °C, and relative humidity is 70%. (b) Exposure time is 2 min, vapor temperature is 15 °C, and relative humidity is 70%. (c) Exposure time is 2 min, vapor temperature is 25 °C, and relative humidity is 90%. (d) Exposure time is 20 min, vapor temperature is 25 °C, and relative humidity is 90%. (e) Exposure time is 20 min, vapor temperature is 15 °C, and relative humidity is 70%. Scale bars are 10 μm in (a1–e1) and (a3–e3), 1 μm in (a2–e2) and 3 μm in (a4–e4).
Mentions: In order to optimize the VIPS parameters for membrane preparation, we systematically investigate the effects of the exposure time, the relative humidity and the vapor temperature of VIPS chamber on the microstructure and performance of the membranes. The FESEM images of the membranes are shown in Fig. 3. The exposure process of casting solution in vapor is the primary difference between VIPS and LIPS; therefore, the exposure time should be very important for the membrane formation. Compared with the microstructure of the membrane prepared with exposure time of 20 min and vapor at 25 °C and 70% (RH) (Fig. 2f), that prepared with exposure time of 2 min and vapor at 25 °C and 70% (RH) is significantly different (Fig. 3a). When the exposure time is 20 min, the magnified FESEM micrographs clearly show that a lot of nanogels are observed on the pore/matrix interface and the surface (Fig. 2f2); however, when the exposure time is 2 min, only a few nanogels are observed on the pore/matrix interface and the surface (Fig. 3a2). This phenomenon gives an effective supplement to the formation of the gating structure. The liquid-liquid phase separation occurs in the membrane-forming solution induced by the water vapor, and then the droplets of the polymer-lean phases disperse in the continuous polymer-rich phases. The mild VIPS process gives enough time for the droplets to coarsen. At the same time, the nanogels tend to move to the matrix/growing phase interface due to its hydrophilic property. In this situation, 2 min may be enough for the formation of droplets of the polymer-lean phases, but cannot support the procedure of large number of nanogels moving to the pore/matrix interfaces. Then, we fix the exposure time at 2 min and adjust the vapor temperature to 15 °C and relative humidity to 90% (RH), separately. On the condition of exposure time of 2 min and vapor at 15 °C and 70% (RH), the membrane morphology turns to be finger-like, typical structure from LIPS (Fig. 3b1). The lower temperature slows down the phase separation process, which makes the droplets of the polymer-lean phases hard to coarsen and solidify. Meanwhile, few nanogels appear on the pore/matrix interfaces because the lower temperature slows down the moving velocity of the nanogels (Fig. 3b2). However, on the condition of exposure time of 2 min and vapor at 25 °C and 90% (RH), the membrane pores on the surface are enlarged (Fig. 3c3), which are in accordance with previously reported work27. The results show that the exposure time of 2 min is too short for the vapor to influence the membrane formation. Although the vapor temperature and relative humidity varies, the ideal membrane structures cannot be achieved with exposure time of 2 min.

Bottom Line: Smart gating membranes, inspired by the gating function of ion channels across cell membranes, are artificial membranes composed of non-responsive porous membrane substrates and responsive gates in the membrane pores that are able to dramatically regulate the trans-membrane transport of substances in response to environmental stimuli.Easy fabrication, high flux, significant response and strong mechanical strength are critical for the versatility of such smart gating membranes.The smart gating membranes with in situ self-assembled responsive nanogels as functional gates show large flux, significant response and excellent mechanical property simultaneously.

View Article: PubMed Central - PubMed

Affiliation: School of Chemical Engineering, Sichuan University, Chengdu, Sichuan 610065, China.

ABSTRACT
Smart gating membranes, inspired by the gating function of ion channels across cell membranes, are artificial membranes composed of non-responsive porous membrane substrates and responsive gates in the membrane pores that are able to dramatically regulate the trans-membrane transport of substances in response to environmental stimuli. Easy fabrication, high flux, significant response and strong mechanical strength are critical for the versatility of such smart gating membranes. Here we show a novel and simple strategy for one-step fabrication of smart gating membranes with three-dimensionally interconnected networks of functional gates, by self-assembling responsive nanogels on membrane pore surfaces in situ during a vapor-induced phase separation process for membrane formation. The smart gating membranes with in situ self-assembled responsive nanogels as functional gates show large flux, significant response and excellent mechanical property simultaneously. Because of the easy fabrication method as well as the concurrent enhancement of flux, response and mechanical property, the proposed smart gating membranes will expand the scope of membrane applications, and provide ever better performances in their applications.

No MeSH data available.


Related in: MedlinePlus