Biocemented aerogel, method of forming same, and material including same

Abstract

Methods of forming biocemented gels are disclosed. Exemplary methods include biomineralizing a hydrogel to form a biomineralized hydrogel. The biomineralized hydrogel can be used to form a biomineralized organogel and / or a biocemented aerogel. Various materials formed using the gels are also disclosed.

Description

[0001] BIOCEMENTED AEROGEL, METHOD OF FORMING SAME, AND MATERIAL INCLUDING SAME

[0002] CROSS-REFERENCE TO RELATED APPLICATION

[0003] This invention claims priority to U.S. Provisional Application No. 63 / 693,894, entitled "BIOCEMENTED AEROGEL, METHOD OF FORMING SAME, AND MATERIAL INCLUDING SAME" and filed September 12, 2024, the disclosure of which is herein incorporated by reference in its entirety.

[0004] STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0005] This invention was made with government support under grant number DE- SC0018368 awarded by the U.S. Department of Energy. The government has certain rights in the invention.

[0006] FIELD OF THE DISCLOSURE

[0007] The disclosure generally relates to methods of forming gels, such as aerogels. More particularly, the disclosure relates to methods of forming gels using nanofibers.

[0008] BACKGROUND OF THE DISCLOSURE

[0009] Due at least in part to their light weight, high porosity, and insulating properties, aerogels can be used in a variety of applications. For example, aerogels have can be used as thermal insulators in window assemblies to increase thermal insulating properties of windows, electrical and / or thermal insulators in construction and manufactured goods, and as filter materials. While some aerogels can work well for some of these applications, some aerogels, such as those produced from (e.g., cellulose) nanofibers, can be relatively fragile and therefore may not be generally suitable for free standing applications, such as for use in construction materials. Various attempts to increase mechanical strength of aerogels can add undesirable weight to assemblies including the aerogel. Accordingly, there is a general desire for improved aerogels or other gels with improved mechanical strength and relatively light weight.

[0010] Any discussion of problems and solutions involved in the related art has been included in this disclosure solely for the purposes of providing a context for the present invention and should not be taken as an admission that any or all of the discussion was known at the time the invention was made.

[0011] SUMMARY OF THE DISCLOSURE

[0012] The disclosure generally relates to methods of forming gels, such as aerogels, and to materials formed using the gels. As set forth in more detail below, the gels can be biocemented to provide additional mechanical strength to the gels, while minimally impacting weight of the gels.

[0013] In accordance with embodiments of the disclosure, a method of forming a biocemented aerogel includes forming a hydrogel from nanofibers suspended in solution, biomineralizing the hydrogel to form a biomineralized hydrogel, and forming the biocemented aerogel using the biomineralized hydrogel. In accordance with examples of the disclosure, the step of forming the hydrogel comprises providing a solution comprising soluble calcium or magnesium halide(s), such as one or more of CaC , CaBrz, MgC , and / or MgBrz. In accordance with further examples of the disclosure, the step of biomineralizing the hydrogel includes exposing the hydrogel to first biomineralizing microorganisms in a first solution to form a partially biomineralized hydrogel and exposing the partially biomineralized hydrogel to second biomineralizing microorganisms in a second solution. In accordance with examples of the disclosure, the first biomineralizing microorganisms and / or the first solution differs from the second biomineralizing microorganisms and / or the second solution. In accordance with further examples, one or both of the first and second microorganisms comprise bacteria, such as CaCC -producing bacteria. For example, the first biomineralizing microorganisms can be or include photosynthetic bacteria, such as cyanobacteria. The second biomineralizing microorganisms can be or include gram positive bacteria or ureolytic bacteria.

[0014] In accordance with examples of the disclosure, the hydrogel can be formed within a mold. This allows formation of gels (e.g., hydrogels, aerogels, or the like) on site and, in some cases, without additional cutting to a desired size.

[0015] In accordance with additional embodiments of the disclosure, a biocemented aerogel is provided. The biocemented aerogel can be formed according to a method described herein. In accordance with examples of these embodiments, the biocemented aerogel can include linked nanofibers having a cross-sectional dimension of about 3 nm to about 6 nm or about 4 nm to about 10 nm.

[0016] In accordance with further examples, a material comprising or formed using an aerogel, as described herein, is provided. The material can be or include, for example, insulating material, filter material, construction material, or the like. A filter can include an aerogel as described herein.

[0017] These and other embodiments will become readily apparent to those skilled in the art from the following detailed description of certain embodiments having reference to the attached figures; the invention not being limited to any particular embodiment(s) disclosed.

[0018] BRIEF DESCRIPTION OF THE DRAWING FIGURES

[0019] A more complete understanding of exemplary embodiments of the present disclosure can be derived by referring to the detailed description and claims when considered in connection with the following illustrative figures.

[0020] FIG. 1 illustrates a method in accordance with at least one embodiment of the disclosure.

[0021] FIG. 2 illustrates hydrogels in accordance with examples of the disclosure.

[0022] FIG. 3 illustrates a reaction mechanism of forming a hydrogel using HCI.

[0023] FIG. 4 illustrates a reaction mechanism of forming a hydrogel using a solution comprising CaCh in accordance with examples of the disclosure.

[0024] FIG. 5 illustrates tensile stress and strain data for aerogels formed in accordance with examples of the disclosure.

[0025] FIG. 6 illustrates force and strain data for aerogels formed in accordance with examples of the disclosure.

[0026] FIG. 7 illustrates compression stress and strain data for aerogels formed in accordance with examples of the disclosure.

[0027] FIG. 8 illustrates modulus and compression strain for aerogels formed in accordance with examples of the disclosure.

[0028] FIGS. 9-12 illustrate biocemented aerogels formed according to examples described herein. It will be appreciated that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help improve understanding of illustrated embodiments of the present disclosure.

[0029] DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

[0030] Although certain embodiments and examples are disclosed below, it will be understood by those in the art that the invention extends beyond the specifically disclosed embodiments and / or uses of the invention and obvious modifications and equivalents thereof. Thus, it is intended that the scope of the invention disclosed should not be limited by the particular disclosed embodiments described below.

[0031] Various examples of the present disclosure generally relate to methods of forming a gel (e.g., a hydrogel, an organogel, and / or an aerogel). The particular examples described below illustrate methods of forming an aerogel. However, unless otherwise noted, examples of the disclosure are not limited to the formation of an aerogel.

[0032] FIG. 1 illustrates a method 100 in accordance with various examples of the disclosure. Method 100 can be used to form a biocemented aerogel. Method 100 includes the steps of forming nanofibers (step 102), oxidizing the nanofibers to form oxidized nanofibers (step 104), forming a hydrogel (step 106), biomineralizing the hydrogel (step 108), forming an organogel (step 110), and drying the organogel (step 112). As illustrated, steps 102, 104, 110 and / or 112 can be optional steps in accordance with examples of the disclosure.

[0033] During step 102, nanofibers can be formed. Alternatively, the nanofibers can be obtained by other means. In accordance with examples of the disclosure, the nanofibers are formed of cellulose material, such as cellulose material obtained from never-dried, demineralized hardwood cellulose pulp. Exemplary nanofibers at various stages of method 100 can have a cross-sectional dimension of about 3 nm to about 6 nm or about 4 nm to about 10 nm. Additionally or alternatively, exemplary nanofibers can have a length of about 500 nm to about 10000 nm or about 1000 nm to about 3000 nm.

[0034] In accordance with examples of the disclosure, the nanofibers are oxidized during step 104 to form nanofibers having oxidized functional groups, such as -COOH functional groups, attached thereto. Such functional groups can facilitate hydrogel formation during step 106. During step 106, a hydrogel is formed using the (e.g., oxidized) nanofibers, which can suitably be suspended in a solution, such as an aqueous solution. FIG. 3 illustrates a more traditional process / reaction mechanism for forming a hydrogel in a solution including HCI. While such techniques can work for various applications, the inventors found that solutions including a water soluble calcium or magnesium halide, such as CaCh can be used to form the hydrogel. The water soluble calcium or magnesium halide can be used for subsequent biomineralizing and therefore may be advantageous. FIG. 4 illustrates a reaction mechanism for forming a hydrogel using a solution comprising CaCh and / or other suitable dissolved salt(s), such as the calcium and magnesium halides noted herein.

[0035] The step of forming a hydrogel can include exposing a dispersion of oxidized nanofibers to a solution comprising, for example, CaCh or other calcium or magnesium halide noted herein. A particular example of forming a hydrogel from TEMPO-oxidized cellulose nanofibers is described in more detail below. In accordance with examples of the disclosure, step 106 is performed using a mold. This allows formation of the hydrogel or subsequently formed gel in a desired shape without additional processing.

[0036] During step 108, the hydrogel is biomineralized to form a biomineralized hydrogel. As illustrated in FIG. 1, step 108 can include two steps: (1) exposing the hydrogel to first biomineralizing microorganisms (e.g., in a first solution) to form a partially biomineralized hydrogel (step 114) and (2) exposing the partially biomineralized hydrogel to second biomineralizing microorganisms (e.g., in a second solution) (step 116). By way of examples, step 114 can be used to provide extracellular polymeric substances to a surface of the hydrogel and step 116 can be used to more rapidly biomineralize the hydrogel.

[0037] In accordance with examples of the disclosure, one or more of the first biomineralizing microorganisms and / or the first solution differ from the second biomineralizing microorganisms and / or the second solution. Using two or more solutions and / or microorganisms can facilitate obtaining a desired degree of mineralization and / or facilitate obtaining a gel with desired properties, such as mechanical strength.

[0038] In accordance with particular examples, the first biomineralizing microorganisms comprise first CaCCh-producing bacteria. The first CaCCh-producing bacteria can be or include, for example, photosynthetic bacteria, such as cyanobacteria. By way of particular example, the first CaCC -producing bacteria can be or include Geitlerinema. The first solution can be or include saltwater growth media, such as A+ media. The growth media can additionally include a dissolved calcium and / or magnesium salt, such as dissolved calcium or magnesium halide (e.g., CaCh). A concentration of the dissolved calcium salt in the first solution can be between about 10 mM and about 100 mM or between about 40 mM and about 60 mM.

[0039] The second biomineralizing microorganisms can include second CaCCh-producing bacteria— e.g., where the second CaCOs-producing bacteria are different than the first CaCOs- producing bacteria. The second CaCOz-producing bacteria can include gram positive bacteria. In accordance with examples of these embodiments, the second CaCCh-producing bacteria comprise ureolytic bacteria. By way of particular example, the second CaCCh-producing bacteria comprise Sporosarcina pasteurii.

[0040] The second solution can include urea. For example, the second solution can include urea, yeast, and a dissolved calcium and / or magnesium salt, such as dissolved calcium and / or magnesium halide (e.g., CaCIz). A concentration of the urea in the second solution can range from about 5 g / L to about 100 g / L or about 10 g / L to about 50 g / L. A concentration of the yeast in the second solution can range from about 0.1 g / L to about 20 g / L or about 1 g / L to about 5 g / L. A concentration of the dissolved calcium and / or magnesium halide in the second solution can be the same or similar to the concentration described above in connection with the first solution.

[0041] Although step 108 is illustrated with two steps, in some cases, step 108 can include a single step or can include more than two steps. Further, steps 114 and / or 116 can be repeated a number of times before proceeding to the next step. For example, step 114 can be performed once and step 116 can be repeated one, two, three, or more times.

[0042] After or at the end of step 108, method 100 can include exchanging the second solution with water, such as 18 mfi water, in preparation for step 110 and / or 112.

[0043] During step 110, solvent in the hydrogel is exchanged for an organic solvent, such as ethanol or the like, to form an organogel. Step 110 can include multiple steps, such as exchanging the solvent with (e.g., 50 / 50) mixture of water and the organic solvent and then exchanging the mixture with the (e.g., 100%) organic solvent.

[0044] After the organogel is formed, the organogel can be dried to form the biocemented aerogel. Thus, the biocemented aerogel is formed using the biomineralized hydrogel described above. The organogel can be dried using one or more of a variety of techniques. For example, the organo gel can be dried using critical point drying, using, for example, carbon dioxide at an initial chamber temperature set at about 5 °C and pressure set at about 800 psi. A more detailed example of critical point drying is provided below.

[0045] Specific Examples

[0046] The examples provided below are merely exemplary and, unless noted otherwise, are not meant to limit the scope of the claims. For example, while the specific examples are illustrated with CaC , other Ca and Mg halide are suitable.

[0047] Nanocellulose hydrogel-aerogel fabrication protocol

[0048] The synthesis of TEMPO-oxidized cellulose nanofiber

[0049] 2,2,6,6-tetramethylpiperidine- 1- oxyl (TEMPO)-oxidized individualized cellulose nanofibers are well-defined rodlike particles with 3-6 nm width and hundreds-to-thousands nanometers length that were synthesized by our lab in SEEL with a two-step process.

[0050] 1. In the first step, TEMPO oxidation of the never-dried demineralized hardwood cellulose pulp (Dragons Paper, Rumford Division, USA) was started in a basic medium with a pH of 10. 100 g pulp, TEMPO (28.92 mg, 0.094 mmol) and NaBr (317.64 mg) were added to the suspension, followed by the addition of 1 M NaOCI solution (10 ml). When the pH drop was less than 0.01 per minute, the solution was transferred to a high-speed blender and blended for 5-10 minutes at 1500 rpm. This broke down the aggregated cellulose fibers and allowed deeper penetration of the oxidation agent into its interior structures. After blending, the solution was returned to stirring and the pH was again adjusted to 10 with lm NaOH. This process was repeated until the pH of the solution dropped less than 0.5 after blending. The solution was centrifuged several times at 9000 rpm for 20 minutes to free it from the excess and unreacted chemicals. The oxidized cellulose nanofibers were then recovered by centrifugation and washed thoroughly with water, which was then mechanically ground once again with a highspeed grinder.

[0051] 2. The second step started with sonication in Branson Sonifier for 15-50 min at 30% amplitude. Oxidation of the unreacted C6 hydroxyl groups of cellulose into C6 carboxylate groups was further performed using NaCIO? as the primary oxidant, with catalytic amounts of TEMPO and NaCIO in water at a pH of 4.8-6.8. TEMPO again allowed for the selective and efficient conversion of the C6 hydroxyl groups. 1 M dibasic sodium phosphate (2.35 ml) and 1 M monobasic sodium phosphate (2.65 ml) solutions were added to 1 g TEMPO-oxidized cellulose nanofiber solution to act as a buffer during the reaction. This was stirred at 500 rpm for approximately 5 minutes and then 20 m L was removed and set aside to dilute the NaOCI later before adding it to the reaction vessel. TEMPO (25 mg) and sodium chlorite (1.13 g) were added to the oxidized cellulose nanofiber dispersions and stirred at 500 rpm for approximately 20 minutes until these additives were fully dissolved. Sodium hypochlorite (0.455 ml) was then added to the 20 ml separate solution. The diluted sodium hypochlorite was then added to the cellulose nanofibers dispersion, and the reaction vessel was immediately sealed with a screw lid. The solution was placed in a water bath at room temperature and stirred at 500 rpm for approximately 30 minutes. The water bath was then heated to 60 °C and the reaction was allowed to run continuously for 72 hours. The solution was then again centrifuged repeated times at 9000 rpm for 20 minutes to filter the excess chemicals out. In the final step, the dispersion was sonicated again with Branson Sonifier for 30 minutes and filtered with Whatman filter paper 2 to get the final oxidized cellulose nanofiber dispersion in water. The TEMPO-oxidized products were cellulose nanorods of controlled 4-10 nm diameter and 1000-3000 nm length, which were then thoroughly washed with water by filtration and stored at 4 °C. The produced CNF-COOH is a transparent and highly viscous material in aqueous dispersion. Moreover, these cellulose nanofibers hold high crystalline and strong nematic anisotropy in their aqueous, hydrogel and supercritical dried form. They are thin nanofibers, mechanically flexible, optically transparent and mesoporous in nature when they form hydrogel / alcogel / aerogel transition which gives them outstanding performance over their counterparts.

[0052] Fabrication of hydrogel from nematic cellulose nanofiber dispersion with CaCIz

[0053] Aqueous (e.g., TEMPO)-oxidized cellulose nanofiber dispersions with a concentration ranging from 1% to 2% were poured into specific cubical inch molds to fabricate cubes of hydrogel. To initiate gelation, 0.1 M CaCIz was first sprayed with a fine mist spray into the top of the dispersion for 30 seconds. The gelation chemistry of TEMPO-oxidized cellulose nanofibers and CaCIz is depicted in Equation (1). Keeping the sprayed CaCIz spread over the dispersion added more CaCIz to diffuse into the interior of the cubicle dispersion. Meantime, gelation starts on the top level of the molded gel and makes a stable gel platform to hold additional amounts of CaCIz solution for propagating the gelation into the interior of the cubicle through diffusion without disturbing the internal dispersed structure of the cubic hydrogel. It was allowed to stand for 60 minutes without any disturbance. The resulting hydrogel was then moved to a 0.1M CaCIz solvent bath for 24 hours in an oven at 40 °C to make sure that the gelation was complete all over the cubic hydrogel. The ensuing rigid hydrogel was taken from the mold and then washed of all the excess chemicals by repeated washing with DI water and shifted to biocementation process. FIG. 2 illustrates hydrogels formed using these techniques.

[0054] R - COOH + HOOC - R + CaCl2— R — CO — Ca — CO — R + 2HCL Eqn (1)

[0055] Hydrogels Biocementation Protocol

[0056] Received hydrogels, sized 1 inch by 1 inch, were biomineralized using a two-step process, first with Geitlerinema growth and second with Sporosarcina Pasteurii. However, as noted above, the invention is not necessarily restricted to such microorganisms.

[0057] Quick Protocol

[0058] 1. hydrogel treated with Geitlerinema in A+ media for 48 hours with flipping to allow for growth on all surfaces of each hydrogel, replacing media after 24 hours.

[0059] 2. 50 mM CaCIz added with fresh media and Geitlerinema allowed to grow for another 24 hours.

[0060] 3. Media pipetted off and replaced with biocementation solution (20 g / L Urea, 2 g / L Yeast Extract, 50 mM CaCIz), and inoculated with Sporosarcina pasteurii.

[0061] 4. Hydrogels incubated for 72 hours, with biocementation media replaced after 24 and 48 hours.

[0062] 5. Final biocemented hydrogel solvent exchanged into 18 mO water and prepared for critical drying treatment. Full Protocol

[0063] 1. Solvent exchange hydrogels into Geitlerinema (cyanobacteria) saltwater growth media. Transfer hydrogels into fresh A+ media. Add media to fully cover gels, 450 mL of A+ media used to cover 25 1 inch by 1 inch gels.

[0064] 2. After 24 hours, refresh A+ media, pouring off and pipetting the remainder to remove all liquid from hydrogel container and replacing with fresh A+ media.

[0065] 3. Pour off and pipette off the remainder to remove all liquid from hydrogels. Transfer hydrogels to 100 mL beaker, 3 gels per beaker. Spin down Geitlerinema preculture (grown at 37 °C under 150 pmol photons m“2s-1from cool white, fluorescent lamps in air (0.04% CO2) for 48 hours), started from a plate. Cells spun for 10 minutes at 4300 rpm. Resuspend cells in fresh A+ media to OD (700) 0.4.

[0066] 4. Pipette 5 mL of Geitlerinema resuspension onto each gel. Pipette slowly to allow for cells to partially remain on top of gels. 15 mL total cell culture used per beaker of 3 gels.

[0067] 5. Place sealed beakers into growth incubator (grown at 37 °C under 150 pmol photons m-2s’1from cool white, fluorescent lamps in air (0.04% CO2)). Grow cells for 24 hours with no shaking or bubbling.

[0068] 6. After 24 hours, flip the gels 180 degrees to allow for Geitlerinema growth without media coverage of the bottom of gels. Pipette 5 mL of the cell solution in the bottom of the beaker onto each gel, pipetting slowly to allow cells to rest on top of the gels. Return to growth conditions.

[0069] 7. After 24 hours, flip the gels back to their original orientation. Add 80 mL of A+ media with 50 mM CaCh to each beaker, enough to fully cover the gels and partially solvent exchange CaCh into gels. Return to growth conditions.

[0070] 8. After 24 hours, pipette off media. Transfer each gel to an individual beaker. Add 20 mL of biocementation solution to each gel, enough to fully cover the gels. Biocementation solution is 20 g / L Urea, 2 g / L Yeast Extract, 50 mM CaC . (No buffer).

[0071] 9. Inoculate gels with Sporosarcina pasteurii from preculture. Preculture growth from freezer stock for 24 hours in 20 g / L Yeast Extract, 10 g / L Urea, and 0.13 M Tris Buffer pH 9 at 30 °C in the dark. Preculture spun down at 4300 rpm for 10 minutes and cells resuspended in 3 g / L Yeast Extract and 20 g / L Urea to OD (600nm) 0.6. 200 uL of this cell solution added to each gel. Beakers sealed and placed into 30 °C dark incubator. 10. After 24 hours, pipette off media from settled beaker. Add 20 mL of fresh biocementation solution to each gel. Beakers sealed and placed into 30 °C dark incubator.

[0072] 11. Repeat step 9 one additional time for a total of 3 biocementation solutions. Grow for an additional 24 hours.

[0073] 12. Remove media from gels by pipetting and rinse gels with 18 mQ water. Pipette off water, then add 20 mL of fresh 18 mQ water to cover each gel.

[0074] 13. Hand off gels for solvent exchange and critical point drying.

[0075] Supercritical drying of biocemented hydrogels of cellulose cubes

[0076] The biocemented cubes were transferred to 50:50 water ethanol proportion and finally the gel is solvent exchanged to 100% ethanol through repeated washing and now the cubical biocemented gel is termed as organogel since it was completely condensed with pure ethanol. This organogel was then moved to supercritical drying in a critical point dryer (CPD) with CO2. In the CPD with the initial chamber temperature set at 5 °C and pressure set at 800 psi. The next step involved purging ethanol from the chamber and replacing it with liquid CO2. Then, the temperature was raised to 40 °C and the pressure was set at 1400 psi and then ethanol leftover was purged while within supercritical phase for 30 minutes. The final step of the process, bleeding of supercritical CO2, was then started slowly, at 25 psi / min, and the chamber was gradually depressurized within about 1 hour. The resulting aerogels were kept at 50 °C for 1 day before characterization and functionalization.

[0077] FIGS. 5-8 illustrate mechanical properties of aerogels formed using the methods described herein.

[0078] Sample ID Guide:

[0079] 1. Control: Sample received solvent exchange in step 1, and then into step 12.

[0080] 2. No Cell Control: Samples received all media but did not receive the Geitlerinema in step 4 (instead receiving fresh A+ media) or the Sporarcina Pasteurii inoculation in step 9.

[0081] 3. Just Geitlerinema: Samples received all treatments up to step 7, and then did not receive any further steps, skipping to step 12. 4. Just Sporarcina Pasteurii (1): Sample received all treatments up to step 9, skipping steps 10-11, except for addition of Geitlerinema in step 4 (instead receiving fresh A+ media). Received 1 delivery of biocementation solution. Sample allowed to grow for the full 72 hours of step 10-11, just no additional media added.

[0082] 5. Just Sporarcina Pasteurii (3): Sample received all treatments except for addition of Geitlerinema in step 4 (instead receiving fresh A+ media). Received 3 delivery of biocementation solution.

[0083] 6. Full Treatment (1): Samples received all treatments except for new media in steps 10- 11. Received 1 delivery of biocementation solution. Sample allowed to grow for the full 72 hours of step 10-11, just no additional media added.

[0084] 7. Full Treatment (3): Samples received all treatments as described. Received 3 deliveries of biocementation solution.

[0085] FIG. 5 illustrates improved stress versus strain data for the modified samples, relative to the unmodified samples. FIG. 6 illustrates improved force versus strain data for the modified samples, relative to the unmodified samples. FIG. 7 illustrates improved compression stress / strain data for the modified samples, relative to the unmodified samples. FIG. 8 illustrates improved compression modulus / strain data for the modified samples, relative to the unmodified samples.

[0086] FIG. 9 illustrates an aerogel that is formed from a hydrogel treated with Geitlerinema and the first solution. As illustrated, the aerogel includes biomineral formations. FIG. 10 illustrates an aerogel formed using a hydrogel treated with Sporosarcina Pasteurii and 1 biocementation media (no Geitlerinema). Again, some biomineralization is noticed. FIG. 11 illustrates a biocemented aerogel formed using a hydrogel treated with Geitlerinema and Sporosarcina Pasteurii and 1 biocementation media. FIG. 12 illustrates an aerogel formed using a hydrogel treated with Geitlerinema and Sporosarcina Pasteurii and 1 biocementation media, illustrating increased biomineralization, compared to FIG. 11. The biocemented aerogels can be used as insulating materials and / or as a filter.

[0087] In this disclosure, any two numbers of a variable can constitute a workable range of the variable, and any ranges indicated may include or exclude the endpoints. Additionally, any values of variables indicated (regardless of whether they are indicated with about or not) may refer to precise values or approximate values and include equivalents, and may refer to average, median, representative, majority, etc. in some embodiments. The term about can refer to ±20, ±10, 5, 2, 1, or 0.5% of the stated value. Further, in this disclosure, the terms including, constituted by, having and related words can refer independently to typically or broadly comprising, comprising, consisting essentially of, or consisting of in some embodiments. In accordance with aspects of the disclosure, any defined meanings of terms do not necessarily exclude ordinary and customary meanings of the terms.

[0088] The present invention has been described above with reference to a number of exemplary embodiments and examples. It should be appreciated that the particular embodiments shown and described herein are illustrative of the preferred embodiments of the invention and its best mode and are not intended to limit the scope of the invention.

[0089] Further examples of the disclosure are set forth in the claims. It will be recognized that changes and modifications may be made to the embodiments described herein without departing from the scope of the present invention. These and other changes or modifications are intended to be included within the scope of the present invention.

Claims

Claims:

1. A method of forming a biocemented aerogel, the method comprising the steps of: forming a hydrogel from nanofibers suspended in a solution; biomineralizing the hydrogel to form a biomineralized hydrogel; and forming the biocemented aerogel using the biomineralized hydrogel.

2. The method of claim 1, further comprising a step of performing a solvent exchange to form an organogel from the biomineralized hydrogel.

3. The method of claim 2, wherein the step of forming comprises critical point drying of the organogel.

4. The method of any of claims 1-3, wherein the step of biomineralizing the hydrogel comprises: exposing the hydrogel to first biomineralizing microorganisms in a first solution to form a partially biomineralized hydrogel; and exposing the partially biomineralized hydrogel to second biomineralizing microorganisms in a second solution.

5. The method of claim 4, wherein the first biomineralizing microorganisms comprise first CaCOs-producing bacteria.

6. The method of claim 5, wherein the first CaCOs-producing bacteria comprise photosynthetic bacteria.

7. The method of claim 5 or 6, wherein the first CaCOs-producing bacteria comprise cyanobacteria.

8. The method of any of claims 5-7, wherein the first CaCOs-producing bacteria comprise Geitlerinema.

9. The method of any of claims 4-8, wherein the second biomineralizing microorganisms comprise second CaCOs-producing bacteria.

10. The method of any of claims 4-9, wherein the second CaCCh-producing bacteria comprise gram positive bacteria.

11. The method of any of claims 4-10, wherein the second CaCCh-producing bacteria comprise ureolytic bacteria.

12. The method of any of claims 4-11, wherein the second CaCCh-producing bacteria comprise Sporosarcina pasteurii.

13. The method of any of claims 4-12, wherein the step of exposing the partially biomineralized hydrogel to second biomineralizing microorganisms in a second solution is repeated one or more times.

14. The method of any of claims 1-13, wherein the hydrogel is formed within a mold.

15. The biocemented aerogel formed according to any of claims 1-14.

16. The biocemented aerogel of claim 15, comprising linked nanofibers having a cross- sectional dimension of about 3 nm to about 6 nm or about 4 nm to about 10 nm.

17. An insulating material comprising the biocemented aerogel of any of claims 15 or 16.

18. A filter comprising the biocemented aerogel of any of claims 15 or 16.

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