User:Kfbrigham/Group sandbox

Scientist and artists have been studying solutions to contemporary challenges in building construction and industrial design that use living tissue instead of inanimate material. Examples include: self-mending biocement, self-replicating concrete replacement, and mycelium-based composites for construction and packaging. Artistic projects include building components and household items.

History
The field of living building materials (LBMs) began with biomimetic mineralization imitating corals. The use of microbiologically induced calcite precipitation (MICP), a form of biomineralization, in concrete was pioneered by Adolphe et al in 1990, as a method of applying a protective coating on building facades. In the 2000s, fungus mycelium-based building materials were introduced. Greensulate, a mushroom-based insulation was developed at Rensselaer Polytechnic Institute in the 2006/2007 academic year. During the late 2000s and 2010s, mycelium composites were developed as packing materials, acoustic absorbers, and structural building materials such as bricks.

In the United Kingdom, the Materials for Life (M4L) project was founded at Cardiff University in 2013 to "create a built environment and infrastructure which is a sustainable and resilient system comprising materials and structures that continually monitor, regulate, adapt and repair themselves without the need for external intervention." ML led to the UK's first self-healing concrete trials. In 2017, M4L was expanded into the Resilient Materials 4 Life (RM4L) consortium led by Cardiff University, the University of Cambridge, the University of Bath, and the University of Bradford and funded by the Engineering and Physical Sciences Research Council. This consortium aims to build on the successes of M4L and "create smart materials that will adapt to their environment, develop immunity to harmful actions, self-diagnose deterioration and self-heal when damaged." RM4L has four research themes: self-healing of cracks at multiple scales, self-healing of time-dependent and cycling loading damage, self-diagnosis and immunization against physical damage, and self-diagnosis and healing of chemical damage.

In 2016, the U.S. Defense Advanced Research Projects Agency (DARPA) launched Engineered Living Materials (ELM) program. This goal of this program is to "develop design tools and methods that enable the engineering of structural features into cellular systems that function as living materials, thereby opening up a new design space for building technology. The program aims to validate these new methods through the production of living materials that can reproduce, self-organize, and self-heal." In 2017, Ecovative Design was awarded a $9.1 million contract funded by the ELM program to "(1) grow a living hybrid composite building material in the field using locally sourced feedstocks, (2) genetically re-program that living material with responsive functionality (wound repair, protective surfaces, and/or infection response, for example), and (3) rapidly reuse and redeploy material into new shapes, forms, and applications." In 2020, a research group at the University of Colorado funded by an ELM grant published a paper after successfully creating exponentially regenerating concrete.

Synthesis and Fabrication
Self-replicating concrete is composed of a hydrogel and sand scaffold. Within the scaffold are synechococcus bacteria. The sand and hydrogel scaffold is used because it is less harsh on the bacteria when compared to a normal concrete environment, and allows for more viability. This scaffold lacks the high pH, ionic strength, and temperatures upon hardening associated with typical concrete paste. The synechococcus bacteria are able to biomineralize calcium carbonate, which is the main contributor to the overall strength and durability of the scaffold, allowing the scaffold to be used as concrete or mortar.

Properties
The bacteria in this material react to humidity changes. The bacteria are most active and reproduce the best in conditions with 100% humidity. As humidity decreases, cell replication and mineralization activity decrease. However, these cells have the ability to create new generations by introducing them to a new sand and hydrogel scaffold and new cellular media. With the beginning of new generations it can be seen that the biomineralization activity of the bacteria increases compared to the prior generation. This allows for faster production and exponential manufacturing growth.

The structural properties of this material are similar to Portland-cement based mortars. Self-replicating concrete has a modulus of 293.9 MPa and can undergo a yield stress of 3.6 MPa. It also has a fracture energy of 170 N. This is much less than most standard concrete, which can reach up to a few kN. While the fracture energy of self-replicating concrete is not similar to that of standard concrete, its maximum stress reaches the minimum required value for Portland-cement based concrete, which is approximately 3.5 MPa.

Uses
This self-replicating concrete can be used in various applications. While cell growth, reproduction, and biomineralization activity are highest at a humidity of 100%, a drop to 50% does not have a large impact on the cellular activity, meaning that this material can be used in most environments. One major factor is how increasing and decreasing the humidity affect the mechanical properties. The cells grow more efficiently in high humidity, but the material is stronger under conditions with low humidity. This means that the application of this material must be tailored to its environment.

This material can be used in more humid environments as a crack filler on roads, walls and sidewalks. The high humidity will allow the cells to grow, creating more calcium carbonate, strengthening the material, and naturally filling in the crack. In drier environments, the self-replicating concrete can be used more structurally, because of the increased strength due to lack of humidity.

Another large upside to this material pertains to the manufacturing. As long as new sand hydrogel scaffolds are introduced, multiple generations can be made from one sample of this material. This means that the self-replicating concrete can be mass produced on an exponential scale, assuming each generation is able to be cared for and properly maintained. Furthermore, the bacteria used to make this concrete absorbs carbon instead of emitting carbon like most cements, which account for 8% of the world's carbon footprint. This self-replicating concrete material is not meant to replace standard concrete, but to open up a new class of materials, with a mixture of strength, ecological benefits, and biological functionality.

Definition
Advancements in optimizing methods to use microorganisms to facilitate carbonate precipitation are rapidly developing. Biocement specifically is a material that is most well known for its self-healing properties due to microscopic organisms such as bacteria and fungi that are used along with calcium carbonate(CaCO3) in the formation process of the material.

Synthesis and Fabrication
Microscopic organisms are the key component in the formation of bioconcrete as they provide the nucleation site for CaCO{sub|3} to precipitate on the surface. Microorganisms such as Sporosarcina pasteurii are useful in these fabrications as they create alkaline environments where high is pH and dissolved inorganic carbon(DIC) count are both high. These factors are essential for micro biologically induced calcite precipitation(MICP) which is the main mechanism in which bioconcrete is formed. Other organisms that can be used to induce this process are photosynthetic microorganisms such as microalgae and cyanobacteria, or sulphate reducing bacteria(SRB) such as Desulfovibrio desulfuricans. The nucleation of calcium carbonate is dependent on four major factors: 1. Calcium concentration, 2. DIC concentration, 3. pH level, and 4. availability of nucleation sites. As long as calcium ion concentration is high enough, the microorganisms previously described can create such an environment through processes such as ureolysis.

Properties
Biocement is able to "self-heal" due to bacteria, calcium lactate, nitrogen, and phosphorus components that are mixed into the material. These components have the ability to remain active in biocement for up to 200 years. Biocement like any other concrete can crack due to external forces and stresses. Unlike normal concrete however, the microorganisms in biocement can germinate when introduced to water. Rain can supply this water which is an environment that biocement would find itself in. Once introduced to water, the bacteria will activate and feed on the calcium lactate that was part of the mixture. This feeding process also consumes oxygen which converts the originally water soluble calcium lactate into insoluble limestone. This limestone then solidifies on surface it is lying on, which in this case is the cracked area, thereby sealing the crack up.

Oxygen is one of the main elements that cause corrosion in materials such as metals. When biocement is used in steel reinforced concrete structures, the microorganisms consume the oxygen thereby increasing corrosion resistance. This property also allows for water resistance as it actually induces healing, and reducing overall corrosion. Water concrete aggregates are what are used to prevent corrosion and these also have the ability to be recycled. There are different methods to form these such as through crushing or grinding of the biocement.

The permeability of biocement is also higher compared to normal cement. This is due to the higher porosity of biocement and this can leader to larger crack propagation when exposed to strong enough forces. The fact that biocement is now roughly 20% composed of a self healing agent also decreases its mechanical strength. The mechanical strength of bioconcrete is about 25% weaker than normal concrete, making its compressive strength significantly lower. There are also some organisms such as Pesudomonas aeruginosa that are effective in creating biocement but are unsafe to be near humans so these must be avoided.

Uses
Biocement is currently used in applications such as in sidewalks and pavements in buildings. There are ideas of biological building constructions as well. The uses of biocement are still not widespread because there is currently not a feasible method of mass producing biocement to such a high extent. There is also much more definitive testing that needs to be done to confidently use biocement in such large scale applications where mechanical strength can not be compromised. The cost of biocement is also twice as much as normal concrete. Different uses in smaller applications however include spray bars, hoses, drop lines, and bee nesting. Biocement is still in its developmental stages however its potential proves promising for its future uses.

Mycelium-Based Composites
Mycelium composites are products that uses mycelium, which is one of the main components of a fungi. Fungus depends on mycelium to get nutrients from the environment. There are several uses of mycelium composites in the industry because it is economically and environmentally sustainable. There are several ways to fabricate and synthesize mycelium composites which can alter the properties to produce different types of materials for different types of uses.

Synthesis and Fabrication
Mycelium- Based Composites are usually synthesized by using different kinds of fungus, especially mushroom. An individual microbe of fungi is introduced to different types of organic substances to form a composite. The selection of fungal species is important for creating a product with specific properties. Some of the fungal species that are used to make composites are ''G. lucidum, Ganoderma sp. P. ostretus, Pleurotus sp., T. versicolor, Trametes sp''., etc. A dense network is formed when the mycelium of the microbe of fungi degrades and colonizes the organic substance. Plant waste is a common organic substrate that is used in mycelium based composites. Fungal mycelium is incubated with a plants waste product to produce sustainable alternatives mostly for petroleum based materials. The mycelium and organic substrate needed to incubate properly and this time is crucial as it is the period that these particles interact together and bind into one to form a dense network and hence form a composite. During this incubation period, mycelium uses the essential nutrients such as carbon, minerals, and water from the waste plant product. Some of the organic substrate components include cotton, wheat grain, rice husk, sorghum fiber, agricultural waste, sawdust, bread particles, banana peel, coffee residue, etc. The composites are synthesized and fabricated using different techniques such as adding carbohydrates, altering fermentation conditions, using different fabrication technology, altering post- processing stages, and modifying genetics or biochemicals to form products with certain properties. Fabrication of most of the mycelium composites are by using plastic molds, so the mycelium can be grown directly into the desired shape. Other fabrication methods include laminate skin mold, vacuum skin mold, glass mold, plywood mold, wooden mold, petri dish mold, tile mold, etc. During fabrication process, it is essential to have sterilized environment, a controlled environment condition of light, temperature (25-35°C) and humidity around 60-65% for the best results. One way to synthesize a mycelium based composite is by mixing different composition ratio of fibers, water and mycelium together and putting in a PVC molds in layers while compressing each layer and letting it incubate for couple of days. Mycelium based composites can be processed in foam, laminate and mycelium sheet by using processing techniques such as laster cutting, cold and heat compression, etc. . Mycelium composites tend to absorb water when they are newly fabricated, therefore this property can be changed by oven drying the product.

Properties
One of the advantages about using mycelium based composites is that properties can be altered depending on fabrication process and the use of different fungus. Properties depend on type of fungus used and where they are grown. Additionally, fungi has an ability to degrade the cellulose component of the plant to make composites in a preferable manner. Some important mechanical properties such as compressive strength, morphology, tensile strength, hydrophobicity, and flexural strength can be modified as well for different use of the composite. To increase the tensile strength, the composite can go through heat pressing. A mycelium composite made out of 75 wt% rice hulls have density of 193 kg/m3, while 75 wt% wheat grains has 359 kg/m3, which shows how different mycelium substance has effect on its property. One the methods to increase the density of the composite would be by deleting a hydrophobin gene. These composites also have the ability of self fusion which increases their strength. Mycelium based composites are usually compact, porous, lightweight and a good insulator. The main property of these composites is that they are entirely natural, therefore sustainable. Other advantage of mycelium based composites is that this substance acts as an insulator, is fireproof, nontoxic, water resistance, rapidly growing, and has an ability to bond with neighboring mycelium products. Mycelium based foams (MBFs) and sandwich components are two common type of the composites. MBFs are the most efficient type because of their low density property, high quality, and sustainability. The density of MBFs can be decreased by using substrates that are smaller than 2mm in diameter. These composites have higher thermal conductivity as well.

Uses
One of the most common use of mycelium based composites is for the alternatives for petroleum and polystyrene based materials. These synthetic foams are usually used for sustainable design and architecture products. The use of mycelium based composites are based on their properties. There are several bio-sustainable companies such as Ecovative Design LLC, MycoWorks, MyCoPlast, etc. that use mycelium based composites that make protective packaging for electronics and food, bricks, leather substitutes, alternatives for floors and acoustic tiles, thermal and acoustic insulation, construction panels, etc. The property of being able to bond with neighboring composite helps the mycelium based composite to form strong bonds for a brick which are widely used. There is a 40 foot tall tower in MoMa PS1 at New York City, Hy-Fi made using 1000 bricks made from corn stalks and mycelium. This product won the annual Young Architects Program (YAP) contest in 2014. There are also other several commonly used products such as lamps, kitchen utensils, ceiling panels, decorative items, fashion items, chair, etc made out of mycelium. In architecture, mycelium based composites are widely used because they have better insulation performance and fire resistance than currently used products. Mycelium is being used more in industry to replace common plastic materials that are harming the environment. These products are manufactured using low energy, natural manufacturing process and are biodegradable.

Further Applications
Beyond the use of living building materials, the application of microbially induced calcium carbonate precipitation (MICP) has the possibility of helping remove pollutants from wastewater, soil, and the air. Currently, heavy metals and radionuclei provide a challenge to remove from water sources and soil. Radionuclei in ground water do not respond to traditional methods of pumping and treating the water, and for heavy metals contaminating soil, the methods of removal include phytoremediation and chemical leaching do work; however, these treatments are expensive, lack longevity in effectiveness, and can destroy the productivity of the soil for future uses. By using ureolytic bacteria that is capable of CaCO3 precipitation, the pollutants can move into the calcite structure, thereby removing them from the soil or water. This works through substitution of calcium ions for pollutants that then form solid particles and can be removed. It's reported that 95% of these solid particles can be removed by using ureolytic bacteria. However, when calcium scaling in pipelines occurs, MICP cannot be used as it is calcium-based. Instead of calcium, it is possible to add a low concentration of urea to remove up to 90% of the calcium ions.

Another further application involves a self-constructed foundation that forms in response to pressure through the use of engineering bacteria. The engineered bacteria could be used to detect increased pressure in soil, and then cement the soil particles in place, effectively solidifying the soil. Within soil, pore pressure consists of two factors: the amount of applied stress, and how quickly water in the soil is able to drain. Through analyzing the biological behavior of the bacteria in response to a load and the mechanical behavior of the soil, a computational model can be created. With this model, certain genes within the bacteria can be identified and modified to respond a certain way to a certain pressure. However, the bacteria analyzed in this study was grown in a highly-controlled lab, so real soil environments may not be as ideal. This is a limitation of the model and study it originated from, but it still remains a possible application of living building materials.