World Toilet Day | With these toilet "black technologies", what is the future of "going to the toilet"?

Today is World Toilet Day. Toilets are closely related to our daily lives, carrying the heavy responsibility of "receiving" human excrement. However, toilets also bring us many troubles. Let's take a look at some toilet "black technologies" and new trends in artificial intelligence (AI) toilets that are expected to solve these troubles!

01 Slide! Slide down quickly!

Once upon a time, there was a joke circulating on the Internet: A person was under great pressure at work, so he ran to the toilet to cry secretly. As a result, every toilet had excrement, and the person became even more upset...

I believe that everyone has had this experience more or less: in the toilet at school or work, you open the door and find that there is still residue in the squat toilet. You are so angry that you flush the water three or four times, but the residue is still there and cannot be flushed away at all! How great would it be if there was such a toilet at this time: smooth as jade, shiny and glossy, and it would not stick to excrement and slide into the water with a "swoosh"! This would not only save manpower for cleaning the toilet, but also effectively save water resources.

The surface of the "slippery" toilet developed by the researchers uses liquid solidified smooth surface (LESS) technology , that is, a new material is sprayed on the surface of the toilet, the main components of which are silicone oil and polydimethylsiloxane [1]. As a sprayable coating, this material can effectively repel rainwater, soapy water, dyed water and synthetic feces . As shown in Figure 1, compared with the best commercial hydrophobic toilets on the market, whether it is water droplets or synthetic feces with a dynamic viscosity covering 9 orders of magnitude (10-3-105 Pa·s), the toilet with LESS coating can achieve a good repellent effect, that is, it can reduce the adhesion of viscoelastic fluids such as feces by about 90%, basically achieving "non-stick". Moreover, the LESS coating is also very effective in saving water resources. Compared with the untreated control surface, the toilet with LESS coating can reduce the amount of cleaning water by about 90%. At the same time, LESS also has good antibacterial properties and durability. I believe that when this coating material is used on a large scale, people will no longer have to "frown" when opening the toilet door.

Figure 1 Comparison of the repellency of toilet liquids and synthetic feces of the most advanced commercial hydrophobic toilet LESS coating (Image source: Reference [1])

02 Use the magic of microorganisms to dispel the "stink"

The main components of toilet odor include hydrogen sulfide, ammonia, methane and other gases. The presence of toilet odor not only affects human health, but also pollutes the environment. Toilet deodorization is also a means to improve the comfort of toileting.

Existing odor control technologies include physical, chemical, and biological methods[2]. Physical methods refer to methods that use physical means to mask, transfer, or dilute odors, such as using aromatic gas substances to cover up odors, using activated carbon to absorb odors, and equipping toilets with ventilation systems. In addition, the gaps under toilet baffles also have ventilation functions. Chemical methods refer to methods that use specific solutions to react chemically with odors. This method is highly efficient and low-cost, and at the same time requires the replacement of absorbents. Attention should also be paid to the secondary pollution caused by the products generated by the absorption of odors.

The biological method refers to the absorption of odor as an energy source for microbial metabolism. The products are generally water and carbon dioxide. This method is low-cost, has good treatment effects and is basically pollution-free. Yan Zhiying's team from the Chengdu Institute of Biology, Chinese Academy of Sciences, recently studied the release pattern of toilet fecal odor and the effect analysis of microbial deodorization [3]. Studies have shown that high temperature and appropriate humidity can intensify the release of fecal odor. For example, some restaurants will pile ice cubes in the urinals of men's toilets, which can achieve the purpose of cooling and reduce the release of odor. Figure 2 shows a schematic diagram of the composite microbial agent prepared in this study for toilet deodorization. It can be seen that the ammonia content in the toilet odor has been reduced by 80%, the hydrogen sulfide content has been reduced by 40%, and some microorganisms can colonize in feces and continue to play a deodorizing role.

Figure 2 Schematic diagram of microbial toilet deodorization (Image source: Reference [3])

03 Prescribe a prescription for the "stubborn problem" of toilet slippage

At the same time, safety hazards in toilets cannot be ignored, especially falls in toilets. According to statistics from the Ministry of Health, fractures and sprains caused by accidental falls account for 35% of all hospitalizations each year, most of which are elderly people and children [4]. The floor is not dry after mopping, rainwater remains after stepping on it in rainy and snowy weather, and toilet pipes leak. Therefore, it is necessary to take anti-slip measures in the toilet, such as using anti-slip tiles, laying anti-slip mats, and spraying anti-slip agents on the toilet floor.

The development of some new anti-skid ceramic functional bricks[5] has brought new hope for curing the "chronic disease" of slipping in toilets. They have a large friction coefficient (the larger the friction coefficient, the better the anti-skid performance). Even if there is water on the brick surface, walking on it will not feel slippery. These new anti-skid bricks use a method of pre-embedding high-melting-point, high-affinity alumina seeds in low-temperature glaze, which causes differences in local composition and temperature at the microscopic level, so that micro-protrusion structures at the micron level can be grown at fixed points. At the same time, a highly closed anti-fouling layer can be formed around the protrusions by reducing the surface energy . Combined with inkjet printing technology, a variety of patterns can be obtained on the surface of the anti-skid bricks. Therefore, such new anti-skid ceramic functional bricks have anti-skid, anti-fouling and beautification functions at the same time.

04 Sit on the toilet and we’ll tell you who you are! Are AI toilets coming?

Digital management in toilets can provide people with more convenient services, thereby improving people's quality of life, such as automatic flushing of urinals and toilets, humidity sensors and gas monitoring sensors in toilets, etc. Recently, researchers have studied an intelligent triboelectric pressure sensor and image sensor for home health monitoring in AI toilets [6].

Common means of identity recognition are based on cameras or radio frequency technology, but their application scenarios are limited due to privacy issues. Based on a triboelectric pressure sensor array, researchers use the different pressures of different users' sitting methods to identify their biometrics, and use deep learning to correctly identify users. As shown in Figure 4, 10 fabric-based sensor array elements are added to the toilet. The pressure stimulation generated when the user sits down induces the charge to flow in the external circuit, thereby converting mechanical energy into electrical energy. The seating habits of different users produce different pressures on sensor elements with different labels. Through AI deep learning, the biometric information of 6 users sitting on the toilet seat can be identified with an accuracy rate of over 90%.

The image sensor used can record the dynamic changes in the user's urine color and perform data analysis. All information collected by the AI ​​toilet system will be uploaded to the server, and users can view it on their mobile devices to continuously monitor their health and obtain valuable clinical information. As a smart home, AI toilets can play a huge potential in medical applications.

Figure 4. Sensor array structure and health monitoring diagram of AI toilet (Image source: Reference [4])

Author: Gao Huang, PhD student in Materials Science, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences

Reviewer: Yao Qiaohong, Senior Engineer, PhD, School of Chemistry and Molecular Engineering, Peking University

Produced by: Science Popularization China

[1]Wang, J., Wang, L., Sun, N. et al. Viscoelastic solid-repellent coatings for extreme water saving and global sanitation. Nat Sustain 2, 1097–1105 (2019).

[2] Fan Jizhong, Cui Xiaomei. Research progress on toilet odor composition and treatment technology[J]. Yunnan Chemical Industry, 2024, 51(09): 16-19.

[3]Lyu, Q., Feng, Z., Liu, Y. et al. Analysis of latrine fecal odor release pattern and the deodorization with composited microbial agent. Waste Management 2024, 178, 371-384.

[4] Phoenix News: Every year, 3 million people are injured by falls, and the disability rate is 30%. Are you still ignoring its harm? [EB/OL] (2018-11-10) [2024-11-19] https://ishare.ifeng.com/c/s/v002BmV0JzYLiDzxOPCbuG0rtaRWhE--6ryhh8p8hF3ws---_g__

[5] Liao Yongkang, Research and development of industrial production technology for new anti-slip functional ceramic tiles. Sichuan Baita Xinlianxing Ceramics Group Co., Ltd., 2019-09-19.

[6]Zhang, Z., Shi, Q., He, T., et al. Artificial intelligence of toilet (AI-Toilet) for an integrated health monitoring system (IHMS) using smart triboelectric pressure sensors and image sensor. Nano Energy 2021, 90, 106517.

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