Team:SZU-China/Fecal Sampling


Fecal Sampling


As an essential part of Gutail Floractory's personalized medicine, we need to conduct regular and long-term fecal metagenomic sequencing for patients. In our opinion, obtaining a convenient, low-cost, and highly concealed stool sampling device is a potential problem and pain point in the process of stool sample collection from patients to sequencing institutions.

Meanwhile, according to our clinical investigation, we learned that the common symptoms of IBD patients included loose stools or pus and blood stools, so we decided to design a stool sampling device based on the above concerns.

To this end, we carried out a series of collections and investigations on the current stool sampling devices on the market.

Fecal Sampling Spoon

Market/product research

Figure 1A is a typical stool sampling spoon in the market, which is an integrated device. In this case, the stool sampling spoon is usually connected to the top of the cover of the sample collection tube. After the stool collection, only the spoon is put back into the collection tube, and the cover is tightened. This device is convenient for solid manure collection, and the integrated design has a low manufacturing cost. However, when the stool collected is sparse, the stool will be challenging to collect.

Figure 1B shows another stool sampling device with a pressure-type design. When the viscosity of feces is too high to shake off from the sampling spoon head, feces can be directly dropped with the spoon head by pressing. This device solves the problem of collecting high-viscosity samples. However, the split design can lead to high manufacturing costs, and the actual production process requires the assembly of the device. It is also challenging to collect loose stools.

Furthermore, some innovative biotechnology companies will use the device shown in Figure 1C, its adopted separation design, using swab collection forming dung, and using disposable dropper collecting stools. This kind of design solves the problem of the collection of loose, but the separation of two devices will lead to a high cost and contamination. Also, it brings the patient the choice of two devices at the same time.

hardware1a hardware1b hardware1c
Figure 1A An integrated stool sampling spoon
Figure 1B A pressure-type stool sampling spoon
Figure 1C A split stool sampler

Design and Validation

Since the end of 2019, the COVID-19 outbreak has enveloped the world in the shadow of the virus, and at the same time, we have become familiar with things we were not used to, such as viral nucleic acid tests and face masks. In the face of the epidemic, the most urgent goal of the medical industry is to obtain high-efficiency and low-cost disposable products. The designs made by excellent engineers for various pain points have also become the inspiration of our hardware design.

In the beginning, we made a variety of ideas for the design of the stool sampling spoon, among which we provided two different design schemes for the number of times the device was used. At the same time, we iterated on our hardware design in the theoretical verification stage.

First generation: Multiple-use scheme with disposable spoon head

We refer to the micropipette commonly used in the laboratory when designing this scheme, hoping to design a spoon-shaped spearhead to simultaneously solve the sampling of formed/unformed feces, as shown in Figure 2. However, we realized that such a design would bring enormous manufacturing costs in subsequent discussions and theoretical verification. Also, it is imperative to ensure the cleanliness of the stool sampling device, while strict sterility could not be guaranteed for the user's use environment. Therefore, it was vital to design a one-off sampling scheme.

Figure 2 Hand-drawn sketch of the first generation stool sampler
The second generation: one-time scheme with a breakable spoon head

As shown in Figure 3, inspired by the breakable nucleic acid swab, we designed a breakable mechanism at the spoon's handle to meet the sampling condition of high-viscosity feces. At the same time, the top of the device is based on the design of a disposable dropper, which can collect formed feces and absorb unformed feces/loose stool through the plastic head. The product adopts a one-piece molding process, the whole device is composed of only one part, so it has lower cost and higher economic benefits. The integrated molding process is also convenient for ethylene oxide sterilization and packaging operations. We decided to use a 12ml flat bottom sample tube as the feces collection device for the sample tube, which has two advantages: 1. The long strip of the sampling tube is easy to break off our spoon head; 2. The long strip sampling tube is conducive to avoid the splashing of fecal preservation liquid.

hardware3a hardware3b
Figure 3A Hand-drawn sketch of the second generation stool sampler
Figure 3B Rendering of the computer modeling of the second generation fecal sampler.

In order to further verify and optimize our design, we used 3D printing technology to produce our products, carried out a series of laboratory tests and field investigations from the two aspects of suction and fracture, and put iterative optimization of our products into practice based on the results.

First of all, due to 3D printing technology problems, we could not integrate the production of our soft glue head and hard spoon body, so we decided to conduct a suction test on the products after printing and assembling, respectively. We first consider testing fluids with different viscosity and select fluids with lower viscosity such as water to simulate watery stool for testing, as shown in Figure 4A. For semi-fluids with high viscosity, the tomato sauce was simulated to conduct tests on unformed soft feces, as shown in Figure 4B. It can be seen that our products have strong suction in the face of fluids with different viscosity.

hardware4a hardware4b
Figure 4A shows the water suction experiment of the second-generation fecal sampler
Figure 4B shows the ketchup suction experiment of the second-generation fecal sampler

After the suction test, we decided to test the breaking mechanism of the handle, as shown in Figure 5. In the actual testing process, we found that due to the design structure and 3D printing accuracy of the breaking mechanism, it could be broken unexpectedly when sampling or adhered to after being broken

Figure 5A shows the test diagram of the breaking mechanism of the second-generation fecal sampler
Figure 5B shows the test diagram of the breaking mechanism of the second-generation fecal sampler from another angle
The third generation: one-time scheme with an optimized scoop head breaking mechanism

After a discussion with the registered structural engineer, we decided to redesign the fracture mechanism. We increase the thickness of the upper edge of the breaking mechanism (assuming that the spoon center is oriented upwards) and decrease the thickness of the lower edge of the breaking mechanism. We hope that when the force on the scoop head comes from the direction of the scoop center (i.e., when collecting feces), the breaking mechanism will not break. When the force of the scoop head is opposite to the direction of the scoop center (i.e., when the scoop head is broken), the breaking mechanism can be broken smoothly.

For finite element analysis using SOLIDWORKS, we used forces 10N (1kg) and 15N (1.5kg) that might occur in actual use by users to simulate the fracture effect of the mechanism within a predictable pressure range shown in FIG. 6A and FIG. 6B.

hardware6a hardware6b
Figure 6A Under the force of 15N, it can be seen through finite element analysis and simulation that the spoon did not break
during fecal sampling because the pressure was concentrated at the lower edge of the breaking mechanism. Figure 6B Under
the force of 10N, the finite element analysis and simulation showed that the spoon did not break during fecal sampling
because the pressure was concentrated at the lower edge of the breaking mechanism.

We reduced the thickness of the lower edge of the broken mechanism and increased the thickness of the upper edge to adapt to our actual situation. Due to the characteristics of material properties, we know that the tension is convenient to break the spoon head under stress, and the pressure will not affect the breaking of the spoon head. It can be seen from the finite element analysis image that when stool samples with high hardness and viscosity are taken, the stress and pressure will concentrate on the lower edge of the fracture mechanism, and the mechanism will not be triggered, as shown in Figure 7A. When the scoop head is broken after fecal sampling, the stress and tension will also focus on the lower edge of the breaking mechanism, which will be triggered, as shown in FIG. 7B. Thus, the hardware we produced initially meets the expectations under laboratory conditions.

hardware7a hardware7b
Figure 7A Sampling hand-drawn sketch
Figure 7B Breaking hand-drawn sketch
The fourth generation: one-time scheme with optimized sample collection amount
and minimum collection amount identification

At gene-sequencing companies, we learned that the sample size for whole-genome fecal sequencing is about 1g (formed fecal) /5ml (unformed fecal), which is the size of a soybean. At the same time, we know a well-established buffer for fecal sample preservation to prevent genomic degradation in fecal samples for possible long-term preservation problems. According to the introduction, stool samples can be preserved at room temperature (25°C) for up to one month under the protection of the preservation solution. To this end, we redesigned our scoop head size so that patients could quickly determine the standard sample size. We have also collected a series of valuable opinions in the Department of Gastroenterology, Hospital of Southern University of Science and Technology, which can make our products close to the needs of doctors and patients, as shown in Figure 8.

Figure 8 Communicate hardware design with doctors and collect feedback

In the field research, we demonstrated the application process of our products and were recognized by doctors and patients. In particular, the doctor praised our stool collector and said that we were very innovative in the design

It is worth mentioning that one patient requested a label on the tube body to determine the minimum amount of unformed stool sampling. We carefully considered this problem, conducted a series of computer stimulations, determined the minimum amount of marking, and chose the hot stamping process over the embossing process to reduce the potential manufacturing cost, as shown in Figure 9A and 9B.

hardware9a hardware9b hardware9c
Figure 9A Hand-drawn sketch of the fourth generation fecal sampler
Figure 9B Rendering of the computer modeling of the fourth generation fecal sampler
Figure 9C Rendering of the computer modeling of the fourth generation fecal sampler
Fecal collection device

Market/product research

To understand the current state of the product, we collected many different types of fecal collection devices. We found that the stool collection device used by many biomedical companies, as shown in Figure 10A, is a simple plastic plate that can collect stools at the lowest cost and can collect loose stools. Obviously, the user will face tremendous difficulties collecting with this device, it will not work on the flushing toilet, and the collection process will be awkward.

Another collection device, as shown in Figure 10B is a plastic device attached to the bottom of the toilet seat, which allows the user to collect his or her feces in a comfortable and dignified manner. This device is also effective in collecting loose stools. Nevertheless, the product needs to be removed and thrown into additional garbage bags after collection. It cannot be used in squatting toilets, especially in rural areas where squatting toilets are widespread. At the same time, its manufacturing cost is high, and plastic products will appear an enormous waste and pollution to the environment.

Figure 10C shows a relatively new product, which is non-woven and pasted on the top of the toilet seat, and can be flushed directly into the toilet after use, and solves most of the problems mentioned above. However, for the producer, the production of the product's subsidence needs to make special mold opening, which leads to poor economic benefit and high cost.

hardware10a hardware10b hardware10c
Figure 10A Stool sampling plastic tray
Figure 10B Advanced stool sampling plastic tray
Figure 10C Stool sampling non-woven fabric tray

Design and Validation

For the same purpose as our design of stool sampling scoop/sampling tube, and to adapt to the above-determined design scheme of stool sampling scoop, we also provide two sets of schemes from different angles based on the results summarized in the survey part.

Scheme 1: Plastic scheme using magic straps

In the design of this scheme, we hope to create enough depth to avoid the sampling spoon head being too long, resulting in the lack of absorbability. Meanwhile, we decide to use the accordion design to reduce the space of the whole device after folding, as shown in Figure 11. In order to pursue higher economic benefits, we choose disposable plastic sheets and low price magic tape as the primary material of the product. However, we found it challenging to assemble the product during simulation, and additional operations to remove and discard the product after use was required, which reduced the user's convenience. So we adopted another design.

Figure 11 Hand-drawn sketch of the plastic scheme using magic straps
Scheme 2: Non-woven fabric scheme based on fabric glue and mask sample design

In the scheme design, we thought about the non-woven KN95 masks. Based on market research to take into account the third device, we decided to adopt the way of stitching two pieces of water-soluble non-woven to produce a sampler. Users only need to open the device when using, tear off the fabric glue, paste it on the toilet. Under the action of tension, the sampling place will automatically open. After sampling, the user only needs to tear off the fabric glue on both sides, throw the device into the toilet and flush, as shown in FIG. 12ABC

The advantages of this device are

(1) The operation cost of direct cutting and stitching/hot stamping is lower than that of opening a model;
(2) It is easy for users to use. Once the device is opened, they only need to operate on the toilet, avoiding potential pollution risk;
(3) The scheme can be applied to most toilet environments, including squat toilets, with a simple design and strong concealment;
(4) The design scheme has a strong bearing capacity, can bear the weight of 1.5kg, and has reasonable practicability.

hardware12a hardware12b hardware12c
Figure12 ABC The stool collector
Figure12 D Stool collector bearing test
Final Product

After a series of scheme designs and verification above, we finally determined our core device design, as shown in Figure 13.

In order to make our products more user-friendly, we decided to consider the whole process of patient sampling and design a whole stool sampling kit for patients to use. In addition to our stool sampling spoon and stool collector, to ensure the sterile collection environment, we support optional alcohol swabs in the kit to complete the cleaning and disinfection of the toilet seat/toilet environment. At the same time, in order to make the collection process cleaner for users and eliminate the trouble of peculiar smells, we also support the selection of activated carbon masks and disposable PVC gloves in the set to facilitate the operation of patients.

In addition, to protect patient's privacy, we specially designed a capsule sample storage device and exclusive patient number for the stool sampling tube of patients after sampling, thus demonstrating our humanistic care for patients and avoiding the potential confusion and embarrassment of patients.

In the end, we integrated our stool sampling kit and designed a container that contained every part of our device to facilitate patients and achieve the goal of "Easy test in one box."

hardware13a hardware13b
Figure13 A Our stool sampling kit
Figure13 B Our stool sampling kit

Considering that our stool collection kit may be applied to people of different ages and educational backgrounds, in order to facilitate users to understand the application process of the kit, we also shot a sampling guide video to facilitate users to operate independently.

Fecal sequencing may still be a relatively new concept to the masses, unlike FMCG products on the Internet. However, we firmly believe that the concept of "prevention rather than cure" of "Healthy China" and the concept of sustainable Development Goals of the United Nations gradually take root in people's minds, as IBD disease is gradually recognized and concerned by the public. More and more people will realize the importance of this technology for intestinal diseases and intestinal microbiome-related diseases. To this end, we will continue to engage with users, constantly collect social voices, and constantly polish products. We will put people first so that gene sequencing will no longer be cold and distant but will truly reach thousands of households, benefiting rapidly industrialized and developing countries and people all over the world.