Bioinspired Fatty Acid Amide‐Based Slippery Oleogels for Shear‐Stable Lubrication

Abstract Liquid‐repellent technology is an efficient means of energy‐saving and biofouling avoidance. However, liquid‐repellent surfaces suffer from inefficient lubricant retention under shear flow and fouling problem in marine environment. Here, the authors demonstrate a fatty acid amide (FAA)‐based oleogel for stable and sustainable lubrication in marine environment. The lubrication management of marine creatures is emulated in synthetic oleogels by incorporating solid (FAA) and liquid lubricants into the molecular meshes of polymeric networks, with the nature‐derived solid lubricant providing multifunctional synergistic effects with liquid oil molecules for slippery property and remarkable anti‐biofouling. The lubricant‐confining gel achieves shear‐stable lubricity with efficient oil management. The oleogel provides continued lubrication without biofouling for approximately 4 months in marine field tests. The gel design provides a new paradigm for sustainable and shear‐stable lubrication in marine environment.

In the region near the test sample (y/H = 0 to 0.1) and acrylic channel surface (y/H = 0.9 to 1), near-wall velocity profiles were measured by adopting a two-frame PTV technique through a peak-intensity-searching algorithm to determine displacements of individual particles3. In the center region of the channel (y/H = 0.1 to 0.9), the captured images were processed with PIV technique (PIVview 2C, PIVTEC, Germany). A multigrid interrogation window was operated with a fast Fourier transform-based cross-correlation PIV algorithm to extract instantaneous velocity fields with an interrogation window size of 64 × 64 pixels with 50% overlapping. The whole velocity profile over the samples in the channel was then obtained by combining the velocity field information obtained by the PIV and PTV techniques. The measured instantaneous velocity fields were ensemble-averaged to obtain the mean velocity field, and the slip length was evaluated.

S1.10. Shear-stable lubrication in cyclic high-speed flow test
The shear-stable lubrication of the FAA-incorporating oleogel surface for a high-speed

S1.11.3. Anti-brown algae bioassay experiment
Haploid gametophyte brown algae (Cladosiphon sp) were used to evaluate the biofouling properties of FAA-incorporating oleogel surfaces. Brown algae were incubated in integrated microbiome resource (IMR) medium at 20 °C under the illumination of 20 μmol photons m −2 s −1 (12 h light:12 h dark). [2] The gametes were finely chopped, and the upper solution was removed using centrifugation. The chopped brown algae were washed three times and diluted to 1 mg/mL with the IMR medium.
FAA-incorporating oleogel-coated glass cover slips (18 × 18 mm, Duran group, Germany) were wiped with an oil paper to remove external oil layer on the surface and placed in 6-well plates. Bare cover glass, FAA-free PDMS, EPCs, OPCs, FAA-free PDMS gel surfaces were tested as control groups. The test samples were cultured with 5 mL of the diluted algae suspension for 48 h at 20 °C under 20 μmol photons m −2 s −1 . The medium was replaced to wash the non-adhesive ones at 20 °C under 20 μmol photons m −2 s −1 . The incubation and observation procedures were performed continuously for 3 weeks.
The samples were then observed using a stereomicroscope (Olympus SZX10, Olympus, Tokyo, Japan) attached to an internet protocol camera (IP 8000; Hanwha Techwin, Changwon, Korea). Field of view was 5.5 × 4.3 mm. The areal coverage of the algae was quantified using Image J software (NIH, Bethesda, MD, USA). S1.12. Long-term marine field test S1.12.
The long-term marine field test in a marine farm was conducted in the Yellow Sea located at the latitude of 36°08'12.5"N and longitude of 126°32'27.4"E near the Korean city of Seocheon. The test place was located next to a seaweed farm (kelp farm), where marine organisms and seaweeds are easily attached to general surfaces. The test samples were installed in a frame. In the frame installation, the films coated on the substrates were exposed to the seawater and the substrates were faced the frame wall. The frame was immersed in seawater at a depth of 1.5 m from sea level. In other words, a hydrostatic pressure of 1.1604 bar was applied to the test samples during the long-term field test. The salinity and temperature of seawater were ranged from 31.5 to 33.0 ppt and from 6.8 to 24.3 °C during the test, respectively. The pH of seawater was 8.1 ± 0.1.
The deposition of marine organisms and seaweeds on the test samples were examined using a digital camera. The marine organisms adhered on acrylic panels were observed using a stereo microscope (Olympus SXZ1). In addition, the marine organisms were further observed using a microscope (BX50, Olympus, Tokyo, Japan) attached to an camera (DP72, Olympus, Tokyo, Japan) with the aid of cellSens software (Olympus, Tokyo, Japan). The field test was conducted continuously for 11 weeks (from 25 March 2020 to 8 June 2020).

S1.12.2. Marine field test attached to an operating ship
The long-term marine field test using a ship was conducted in the Yellow Sea located at the latitude of 36°08'12.

S2. Supplementary Notes Supplementary Note S1
Diffusive transport of oil molecules in FAA-incorporating oleogels Oil transport in polymeric gels is linked to their swollen behavior. Oil molecules are diffused into the molecular matrix of FAA-incorporating composites, because polymer chains extend to maximize the interaction between a compatible solvent and cross-linked PDMS polymer network. [3] The temporal swelling behavior of FAA-incorporating composite films in a silicone oil bath was measured to characterize the diffusive transport of oil molecules into the molecular matrix of the FAA-incorporating composites. In this experiment, the FAAfree PDMS film with ca. 0.021 mm thickness, EPC5.0 with ca. 0.017 mm thickness, and OPC 5.0 with ca. 0.017 mm thickness were immersed in silicone oil with a viscosity of 5 cSt. The swollen geometry of a thin polymer film in swelling solvent was previously correlated with solvent diffusion as follows 7 : where L 0 is the initial length of the film, L(t) is the length of the swollen film at swollen time t, L ∞ is the saturated length of the swollen film, S(t) is the transient swelling ratio (=L(t)/L 0 ), S ∞ is the saturated swelling ratio (=L ∞ /L 0 ), d is the film thickness, and D is the diffusivity.
Thus, the relative swelling ratio, (S(t)-1)/(S ∞ -1), of FAA-free PDMS, EPC5.0, and OPC5.0 films were plotted as a function of √ . The relative swelling ratio presents a linear dependence on √ in the initial transient swelling region. In this region, the slope (θ) of the swelling curve was obtained by linear curve fitting. Thus, the diffusivity of oil molecules in each polymer film was extracted from the slope as follows:

Effect of FAAs on oil management in FAA-incorporating oleogels
Effect of FAAs on the oil management in FAA-incorporating oleogels was deeply elucidated using synchrotron wide-angle X-ray scattering (WAXS) experiments. WAXS technique hs been utilized for conformational analysis of flexible polymers like PDMS. [5] The spatial correlation between polymeric chain segments was analysed by obtaining the spacing distance (d-spacing) as follows: ( where d-spacing is the spatial correlation distance between chain segments, and q max is the scattering vector (q) at the maximum scattering intensity (I max ) of the broad peak.
Firstly, the initial spacing distances of dry-state polymeric chains were investigated for FAA-free (PDMS) and FAA-incorporating (EPC and OPC) films without impregnation of silicone oil. WAXS profiles of the FAA-free PDMS displayed a broad maximum PDMS peak at q max value of ca. 0.84 Å -1 (Fig. 2d in the manuscript), which is commonly observed in Xray diffraction (XRD) and small-angle X-ray scattering (SAXS) at high q-range (q ≈ 0.84~0.87 Å -1 ). [6] The position (q max ) of the PDMS peak slightly shifted to lower q values in the FAA incorporation (erucamide for EPCs and oleamide for OPCs), indicating a decrease in the equivalent spacing distance (see d-spacing plot in Fig. 2f of the manuscript).
After impregnation of silicone oil (PDMS liquid, with viscosity of 5 cSt) into each solid film, silicone oil molecules are penetrated into each molecular matrix with a swelling process. The positions (q max ) of the PDMS peak shifted to higher q values from dry state to gel state, indicating a decrease in the spacing correlation distance between polymeric chain segments. After oil penetration into the PDMS, the polymeric skeleton of the PDMS swells as shown in Fig. 2b of manuscript, which induces an increase in interplanar spacing of PDMS chains. However, the spacing distance for FAA-free (PDMS gel) and FAA-incorporating (EPC gels and OPC gels) oleogels decreased because of the spatial correlations between the penetrated oil chains in molecular matrix (comparison of d-spacing in Fig. 2f of the manuscript) of the oleogel. In particular, the spatial correlation distances for the FAAincorporating oleogels was smaller than for the FAA-free oleogel and linearly decreased with increasing the FAA content in the gel. Accordingly, when FAA chains are incorporated into the PDMS network, oil molecules become more densely packed in the crosslinking gel network.

S3.2. NMR spectra of FAA-incorporating PDMS composites
The unsaturated FAAs were incorporated into PDMS to form diverse FAA-incorporated composites. The chemical structure of the FAA/PDMS composites was investigated by 1 H NMR spectrum. In the 1 H NMR spectrum of the oleamide, the C=C bond (marked as 'f') of the oleamide exhibited a peak at 5.37 ppm (Fig. S2).

S3.3. Surface morphology of FAA-incorporating composite surfaces
The surface roughness of a solid can affect its surface energy that is correlated with the contact angle of a liquid. In addition, the surface roughness can affect the friction

S3.4. Chemical composition of FAA-incorporating composites
The chemical composition of the FAA-incorporating composites was analysed by attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy. The spectrum of the FAA-free PDMS showed characteristic peaks (indicated by black arrows in Fig. S4) located at 1014 and 1070 cm -1 (Si-O-Si symmetric and asymmetric stretching, respectively), 1410 cm -1 (asymmetric bending of CH 3 groups), and 2906 cm -1 (symmetric stretching of CH 3 groups). [7] All the characteristic peaks of the PDMS were found in the FTIR spectra of the In the TGA curve of the EPC5.0 (blue curve in Fig. S5(b)), the weight loss started from 240 to 300 °C for the erucamide and continued from 300 °C for the PDMS, indicating the disintegration of the erucamide and PDMS polymer chains. Accordingly, the weight loss of the EPC could be attributed to rapid decomposition of the erucamide (from 240 °C to 300 °C) and gradual decomposition of the PDMS (from 300 °C to 800 °C). In addition, the initial weight loss of the EPC5.0 (from 240 to 300 °C) was ca. 5 %, which confirms the erucamide content (5 wt%) of the EPC5.0.

S3.5. Flexibility and elasticity of FAA-incorporating oleogels
The FAA-incorporating oleogels showed good mechanical stability with a bending radius of ca. 0.18 cm and weight load of 2 kg in the bending (Fig. S6(a)) and compression ( Fig. S6(b)) tests, respectively. In addition, a tensile test was conducted to quantitatively estimate the mechanical property of the FAA-incorporating oleogel. In the stress-strain curve of the EPC5.0 gel, a fracture strain of 80 % occurred with the stress of 0.21 MPa (Fig. S6(c)).

S3.7. Surface wettability of FAA-incorporating oleogels
The surface wettability of FAA-incorporating oleogels was evaluated by measuring the static contact angle of a water droplet on each surface. The FAA-free PDMS had a water contact angle (CA) of approximately 111°, indicating its hydrophobicity ( Fig. S8(a)). EPC and OPC surfaces showed slightly higher and lower CA values, compared with the FAA-free PDMS, respectively. However, both EPCs and OPCs still exhibited hydrophobicity. After hydrophobic silicone oil was impregnated into each surface, the CAs of each oleogel surface were measured after removing an external oil layer on the surface. The overall CAs of the FAA-free (PDMS gel) and FAA-incorporating (EPC gels and OPC gels) oleogels slightly decreased compared to the case of the counterpart solid surfaces (Fig. S8(b)).
In addition, the CA differences among the oleogels with different FAA types (FAA-free,

S3.8. Dual penetration of fatty acid amide and oil molecules in PDMS network
In the view that polymeric skeleton dominates mechanical properties of gels, the storage modulus (G′) and loss modulus (G″) values can represent the structural variation of polymer network. Accordingly, the rheological properties of the FAA-free PDMS, FAA-free PDMS gel, EPC5.0, and EPC5.0 gel were measured (Fig. S9).

S3.9. Swelling ratio of the wall structure in FAA-incorporating oleogels
To estimate the swelling behavior of wall structure in FAA-incorporating oleogels, the FAAfree oleogel (PDMS gel) was prepared as a control sample. In the view of the excellent solvent compatibility of PDMS, PDMS is amenable to solvent infusion due to its low rotational energy barrier of ca. 3.3 kJ/mol around the Me 2 Si−O bond (compared with ca. 13.8 kJ/mol around −CH 2 − in polyethylene); this low energy barrier allows easy diffusion throughout the polymer matrix. [3] The PDMS become swollen and expanded when immersed in a compatible solvent, such as silicone oil, because polymer chains extend to maximize polymer−solvent interactions. [4] Therefore, the swelling behavior of the wall structure in the FAA-incorporating oleogels could be revealed by the swelling ratio of the PDMS.
For the swelling process of the FAA-free and FAA-incorporating oleogels, silicone oil with a viscosity of 5 cSt was used as a swelling solvent. The EPC5.0 gel film exhibits repeatable shrinking-swelling behaviour with a thickness change between ca. 0.15 mm to ca.
0.26 mm (Fig. S10(a)). The swelling ratio was calculated along the dimension of thickness as follows:

( )
where d dry is the initial thickness of a dried state film and d oil is the thickness of an oilimpregnated gel-state film. The film thickness was measured using a profilometer with an accuracy of 0.1 μm. The measured swelling ratios of the FAA-incorporating oleogels (ca. 168 % for the EPC5.0 gel) were higher than that of the FAA-free oleogel (ca. 114% for the PDMS gel) (Figs. S10(b) and 10(c)). Accordingly, these high swelling ratios of the FAAincorporating oleogels are attributed to the swollen property of the PDMS and additional swollen effect induced by the incorporation of the FAAs.

S3.11. Elasticity of FAA-incorporating oleogels
The elastic properties of FAA-incorporating oleogels were evaluated by elastic moduli (Young's moduli) obtained from the tensile stress-strain curves in Fig. S11 S12(b)). In addition, the Young's moduli of OPC gels and EPC gels further decreased, which was approximately 3.9~6.9 times smaller than that of a FAA-free oleogel (PDMS gel) (Figs. S12(c) and S12(d)). Accordingly, the FAA-incorporating oleogels exhibits more elastic properties than the FAA-free oleogel.

S3.12. Water repellence of FAA-incorporating oleogels
To estimate the water repellence of FAA-incorporating oleogels, dynamic contact angles (CA) and sliding angles of a water droplet on the tilted FAA-incorporating oleogels were measured. When a water droplet slides on each surface, advancing CA and receding CA of the sliding water droplet were measured. Contact angle hysteresis (CAH) is the difference between the measured advancing and receding CAs of a moving water droplet, which is qualitatively related with droplet mobility against resistance. [9] Sliding angle is the tilted angle of a surface required for moving a water droplet on it. Low values of CAH and sliding angle indicate a liquid-repellent surface with little pinning of droplets. [9] To confirm the lubrication effect of FAAs as slip agents, CAH and sliding angle were measured for FAA-free and FAA-incorporating surfaces. The CAH values of the OPCs and EPCs were approximately 1.9~2.4 times lower than that of the FAA-free PDMS (Figs. S13(a) and S13(b)). The low CAH values of the OPCs and EPCs resulted in low sliding angle of a water droplet (Fig. S14(a)). Accordingly, the low CAH and sliding angle of OPCs and EPCs demonstrated the lubricant property of FAAs.
In addition, the FAA-free and FAA-incorporating oleogels showed lower CAH and sliding angle than the counterpart FAA-free and FAA-incorporating solid surfaces (Figs. S13(c), S13(d), and S14(b)). In particular, the FAA-incorporating oleogels (OPC gels and EPC gels) exhibited lower CAH and sliding angles than the FAA-free oleogel (PDMS gel), indicating the high water repellence of FAA-incorporating oleogels. Accordingly, the water repellence of the FAA-incorporating oleogels was amplified by integrating FAAs and oil molecules in the hybrid configuration.

S3.13. Solubility of FAA for silicone oil
The solubility of FAA for silicone oil was evaluated by mixing 3g of oleamide powder with 10ml of 5 cst silicone oil (Fig. S15(a)). The mixed oleamide powder with silicone oil was stored at room temperature ( Fig. S15(a-i)) and in a 60°C oven (Fig. S15(a-ii)) for 1 day. Even after 1 day storage in a 60°C oven, the oleamide powder was barely dissolved in silicone oil, indicating extremely low solubility of FAA in silicone oil.
The solubility of FAA in silicone oil was further investigated by impregnating a bare PDMS with the silicone oil containing oleamide powder. After 1-day storage in Fig. S6(a-ii), the silicone oil mixed with oleamide was impregnated into the bare PDMS. The surface characteristics of the PDMS impregnated with the mixed silicone oil was evaluated by measuring its water contact angle (Fig. S15(b)) and sliding angle (Fig. S15(c)). The PDMS impregnated with the mixed silicone oil (red-dotted line in Fig. S15(b, c) showed similar water contact angle and sliding angle with those of the FAA-free PDMS oleogel (black triangular symbol in Fig. S15(b, c)). This result indicates that the solubility level of FAA in

S3.14. Slip flow over FAA-incorporating oleogel surfaces
The highly slippery feature of FAA-incorporating oleogels enables slip phenomena on its surface. To prove the slip phenomena on the oleogel surface, the velocity field over the oleogel surface was visualized. The oleogel surface was placed on the bottom of a channel (10mm wide and 10mm high) and tracing particles were seeded in the working fluid flowing at a Reynolds number of 50 in the channel (Fig. S16(a)). At a fully-developed region, velocity profiles of the flow in the channel center and near-wall regions were measured by using particle image velocimetry (PIV) and particle tracking velocimetry (PTV) techniques, respectively. The measured streamwise velocity (u) was normalized by the time-averaged maximum velocity (u max ). The normalized streamwise velocity profile according to the normalized height of the channel is shown in Fig. S16

S3.15. Liquid repellence of FAA-incorporating oleogels
FAA-incorporating oleogels exhibited highly slippery properties against water. Water is a low viscous fluid that has a low resistance to shear forces and is easy to move molecules. In addition, the FAA-incorporating oleogels were repellent to highly viscous liquid such as honey, non-Newtonian liquids such as ketchup and honey, and milk (Fig. S17). Accordingly, the FAA-incorporating oleogels exhibited high liquid repellence.  Fig. S14(a)).

S3.17. Anti-bacteria property of FAA-incorporating oleogels
To evaluate the antifouling and antimicrobial activity of FAA-incorporating oleogels, Gramnegative E. coli (Escherichia coli) bacteria were cultured on various oleogels and control surfaces ( Fig. S19(a)). After 24 h incubation, E. coli cultured on EPC surfaces (Fig. S19(a-ii)) showed decreased adhesion compared to that grown on a FAA-free surface (PDMS, in Fig.   S19(a-i)). In addition, OPC surfaces showed decreased adhesion as well (Fig. S19(a-iii)).
Those When the solid surfaces were organogelated through the impregnation of silicone oil, the bacterial adhesion on the oleogels was significantly reduced compared to the case of the counterpart solid surfaces (Fig. S19(a-iv, v, and vi)). It is notable that E. coli on a FAA-free oleogel (PDMS gel) were all alive, as evidenced by the green fluorescence emitted ( Fig.   S19(a-iv)). This indicates that oleogels suppress the bacterial attachment with its antifouling capability, rather than killing the bacteria. The impregnated silicone oil in the oleogels is nonfluorinated hydrophobic lubricant with non-toxicity, while most reported slippery liquidinfused porous surfaces (SLIPS) used fluorinated lubricants such as DuPont krytox oils and 3M fluorinert FC-70 whose perfluoroalkyl building blocks can induce toxicity issue and ecological impacts 22, 23 .
In particular, the FAA-incorporating oleogels (EPC gels and OPC gels) exhibited higher antifouling effects than the FAA-free oleogel. Accordingly, the anti-biofouling performance could be amplified by integrating FAAs and oil molecules in the hybrid configuration. In particular, all the FAA-incorporating oleogels with different FAA content exhibited zeroattachment of bacteria on their surfaces, which demonstrates their superior antibiofilm formation capability.

S3.19. Anti-brown algae bioassay experiment
Haploid gametophyte brown algae (Cladosiphon sp) were cultured on various oleogels and control surfaces to assess the anti-biofouling property of FAA-incorporating oleogels ( Fig.   S21(a)). After 24 h incubation, brown algae cultured on both EPC and OPC surfaces were sharply less than those grown on a FAA-free surface (PDMS). These low adhesion of brown algae on the EPCs and OPCs demonstrates the intrinsic antifouling nature of FAAs. The antibiofouling properties of FAAs were quantitatively confirmed through the coverage area of the attached algae ( Fig. S21(b)). The EPCs and OPCs with higher FAA content exhibited higher anti-biofouling property against brown algae.
After organogelation, the algae adhesion on the FAA-free and FAA-incorporating oleogels was slightly reduced compared to the case of the counterpart FAA-free and FAAincorporating solid surfaces ( Fig. S21(a)). In particular, the reduction rates of brown algae

S3.20. Optimum surface energy of FAA-incorporating oleogels for anti-bioadhesion
The surface energy of FAA-incorporating oleogels was estimated from measured static contact angles (CA) (Supplementary Fig. S8) and water surface tension as follows: where θ denotes the water contact angle, γ s is the surface energy of a substrate, γ l is the surface energy of water (72.8 mJ/m 2 ), β is a constant value of 1.057 × 10 -4 m 2 /mJ. [10] Based on the above equation, a substrate with a high CA has low surface energy. The low surface energy can be related to low adhesion for marine biofoulants. [11] The FAA-free (PDMS) and FAA-incorporating composites (EPCs and OPCs) had low surface energy due to their hydrophobicity, compared to case of a hydrophilic acrylic surface ( Fig. S22(a)).
After organogelation, the surface energy range of the FAA-incorporating oleogels (EPC gels and OPC gels) was from ca. 19.7 to 27.3 mJ/m 2 ( Fig. S22(b)). The FAA-free oleogel (PDMS gel) had surface energy of ca. 17.5 mJ/m 2 . According to the Baier curve (bioadhesion curve versus surface free energy in the range of 10 to 70 mJ/m 2 ), minimum bioadhesion did not occur at the lowest surface energy, but occurred in the optimum energy range (from ca. 20 to 30 mJ/m 2 ). [12] The surface energy values of the EPC gels and OPC gels belong to the optimum surface energy range for the minimum bioattachment. Accordingly, in terms of surface energy, the FAA-incorporating oleogels are more suitable for anti-biofouling than the FAA-free oleogel.

S3.21. Low pull-off force of FAA-incorporating oleogels
The cooperation effects of low elastic modulus and low surface energy of FAA-incorporating oleogels on anti-biofouling performance can be evaluated by Griffth's theory of rupture as follows: √ where F is the stress at fracture, A is the flaw length, E is the Young's modulus, and γ is the surface energy density. [13] From the above equation, √ indicates a pull-off force required to separate foulants from the surface. The pre-measured and calculated surface energy ( Supplementary Fig. S22) and Young's modulus ( Supplementary Fig. S12) of each oleogel sample were used for the calculation of each pull-off force.
The FAA-incorporating composites (OPCs and EPCS) had lower pull-off forces than FAA-free surface (PDMS) (Fig. S23(a)). The pull-off force of EPC5.0 was approximately 1.6 and 107 times lower than those of the FAA-free PDMS and acrylic surface, respectively.
After organogelation, the pull-off force of EPC gels and OPC gels further decreased ( Fig.   S23(b)). The pull-off force of EPC5.0 gel was approximately 1.8 and 136 times lower than those of the FAA-free oleogel (PDMS gel) and acrylic surface, respectively. These low pulloff forces of FAA-incorporating oleogels help to mitigate the adhesion of foulants and prevent biofouling. In particular, those effect of low pull-off force on anti-biofouling could be maximized in marine environment with high turbulence intensity, where turbulent flow give rise to a variety of fluid/solid interactions.

S3.22. Long-term marine filed test near sea farm
The long-term marine field test was conducted in the Yellow Sea at the latitude of 36°08'12.5"N and longitude of 126°32'27.4"E near the Korean city of Seocheon (detailed experimental conditions in Supplementary Methods). The field test place was located next to a seaweed farm (kelp farm), where marine organisms and seaweeds are easily attached to the surfaces. Test samples were mounted in a frame and immersed in seawater at a depth of ca.
1.5 m from sea level (Fig. S24(a)). In other words, a hydrostatic pressure of ca. 1.160 bar was applied to the test samples during the long-term field test.
The long-term field test was conducted for 11 weeks (from 25 March 2020 to 8 June 2020).
The acrylic, FAA-free PDMS, OPCs, EPCs with different FAA content were installed in 'A' region ( Fig. S24(a, b)). The FAA-free (PDMS gel) and FAA-incorporating (OPC gels and EPC gels with different FAA content) oleogels were installed in 'B' region ( Fig. S24(a, c)).
After 11 weeks, marine organisms and seaweed were heavily deposited on the solid surfaces ( Fig. S15(a)). To identify biofouling environmental conditions in the field test, the marine biofouling organisms attached on the solid surfaces were analysed. The various biofilm composites were observed including marine bacteria, diatoms, and filamentous red algae (Figs. S26(a) and (b)). Under this extreme biofouling condition, EPC and OPC surfaces exhibited relatively higher biofouling performance than the acrylic and FAA-free PDMS surfaces (see Figs. S25(b, c)). All the EPCs (Fig. S25(b)) and OPC2.5 (Fig. S25(c)) coated on acrylic plates were detached from the substrate due to the adhesive problem. However, the undetached OPC surfaces (5.0, 7.5, 10 wt%) showed relatively clean compared to the acrylic and FAA-free PDMS surfaces, confirming the long-term anti-biofouling property of FAAs ( Fig. S25(c)).
Surprisingly, the FAA-incorporating oleogels showed high anti-biofouling properties with preventing the attachment of marine organisms ('B' region in Fig. S19(a), and Fig. S25(d)).
The overall FAA-incorporating oleogels (EPC gels and OPC gels) remained their clean surfaces compared to the FAA-free oleogel (PDMS gel), which indicates the durable lubrication property of the FAA-incorporating oleogels in the marine environment. For the case of OPC10 gel, the OPC10 gel film was detached from the aluminium substrate, which results in foulant attachment on the substrate. In particular, the EPC5.0 gel exhibited the highest anti-biofouling performance with little biofilm attachment, demonstrating its outperforming sustainability of the anti-biofouling property.

S3.23. Long-term marine field test attached to an operating ship
The long-term marine field test using a ship was conducted at west sea located at the latitude of 36°08'12.5"N and longitude of 126°32'27.4"E near the Seocheon town in Korea.
The As shown in Figs. S27(b) and S27(d), the surfaces of the ship were covered by seaweed for 1 month, which shows the requirement of efficient biofouling technology on the commercial ship. The EPC surfaces exhibited relatively higher biofouling properties than the ship surfaces and FAA-free PDMS, indicating the long-term and shear-stable anti-biofouling property of FAAs (Fig. S27(e)). All the OPC surfaces were detached from the surfaces.
Surprisingly, the EPC5.0 gel surfaces exhibited almost zero-attachment of marine organisms for 4 months as shown in Figure 5e of the manuscript, demonstrating its sustainable and shear-stable multifunctional lubrication property.

S3.24. Diverse substrate compatibility of FAA-incorporating oleogels
FAA-incorporating oleogels can be applied to a variety of materials with the aid of primer as follows ( Fig. S28(a)): firstly, primer solution was coated on a target substrate. After curing the primer at room temperature, the FAA-incorporating composite solution was coated and cured. The cured composite surface was impregnated with oil. Based on this coating strategy, the FAA-incorporating oleogels were successfully coated on different types of substrates including metal, glass, and plastic, indicating diverse substrate compatibility (Figs. S28(b) and S28(c)).

S3.25. Scalability of FAA-incorporating oleogels
FAA-incorporating oleogels can be scalable using a low-cost doctor-blade coating process for large-scale fabrication ( Fig. S29(a)). The doctor-blade coating is a scalable, simple, low-cost, low temperature, solution-based thin film deposition technique that can be compatible with a roll-to-roll fabrication process of large-area films with high throughput. [14] A large scale FAA-incorporating oleogel was fabricated as follows: firstly, FAA-incorporating composite solution was dropped onto a substrate and swiped linearly by a doctor blade. After curing the spread solution, oil was spontaneously infused into the FAA-incorporating composite film by simply immersing the film into an oil bath. Based on this coating process, a large-area FAAincorporating oleogel film with a size of 90 × 60 cm 2 was successfully fabricated ( Fig.   S29(b)).