Assembly and Testing
Assembly
The
development of TriMask will require two (2) major processes: the production of
plant-based wax and manufacturing of the mask itself.
A. The
production of plant-based wax. Due to the
abundance and its rapid growth on nearly everywhere in the Philippines, the
taro plant will be used as the primary element for bio-wax production.
1. Harvesting.
The heart-shaped taro (Colocasia
esculenta) leaves will
be harvested from a local plantation in Cavite.
2. Preparation. Collected leaves will undergo preliminary
processes before proceeding to wax extraction. Leaf sample preparations include
washing and slicing. (a) Wash the leaf sample under running water for at least 3
minutes or until soil and other unnecessary fragments are removed, and (b)
slice the leaf sample into smaller pieces with an about 0.25 x 0.25 in
measurement.
3. Extraction. In a rotary bottle, prepare 500mL of
chloroform, immerse the taro leaf sample, place it into the rotary evaporator,
and raise the temperature to 50°C for 30 seconds until the solvent is evaporated
(Nasri et al., 2014).
4. Storage.
After evaporation, bio-wax is obtained.
Collect, transfer, and store on an amber jar in a cool, dry place.
B. B. Manufacturing
of the TriMask.
All kinds of face masks are designed to obstruct the
proliferation of respiratory droplets. Although cloth face masks are washable
and reusable, it is notable that this lacks standardization in terms of design
and should be regulated for its low efficacy in protection against microscopic
droplets (Ju, Boisvert & Zuo, 2021). Thus, there are several tests needed
to employ in accordance with the American Society of Testing and Materials (ASTM)
to assure its efficiency. These are: (1) particle filtration efficiency, (2) bacterial
filtration efficiency, (3) differential pressure, and (4) fluid resistance.
Particle
Filtration Efficiency (PFE)
PFE test assesses the nonviable particle retention of the filtration device being used in a face mask under a constant airflow rate (Chua, 2020). Figure 1 shows the experimental setup for PFE using polystyrene latex particles at airflow velocity, which are recommended by U. S. Food and Drug Administration (FDA) and ASTM, respectively. For quantification of the filtration efficiency (E), the light scattering method is used by the relationship of the upstream feed (Mu) and downstream filtrate (Md) concentrations (Chua, 2020), which is shown in equation 1. The penetration of the molecules (P) through the mask can also be quantified using equation 2. Thereby, an inverse relationship between filtration efficiency and penetration is observed – the greater the efficiency, the better the performance of the mask in filtering submicron particles.
The process of the PFE are as
follows (ASTM F2100, 1980):
(1)
Situate the TriMask on
the filter holder of PFE tester.
(2)
Interact with the instrument
to initiate the filtration.
(3)
Document the result
presented on the screen of PFE tester.
Bacterial
Filtration Efficiency (BFE)
BFE assesses the mask's ability to filter the aerosol particulates at 3 microns. This signifies the filtration of bacteria that attempts to pass through the mask. Figure 3 shows the setup for the BFE, where aerosolized particles were to be delivered to the sample, filter sheet of TriMask, at a constant flow rate (Chua, 2020). A six-stage Andersen sampler that contains an agar plate, a medium for bacterial growth, where the forming colonies of bacteria would be observed (Xu et al., 2013). The BFE can be obtained using equation 3, where C is the number of colonies in the control plate and F is the number of colonies in the filter. The minimum BFE of 95% should be possessed by a surgical mask (Tessarolo et al., 2021). Consequently, the filtration system of the surgical mask would be imitated by TriMask, which should have the same BFE percentage.
The process of the BFE are as
follows (Eurofins,2020):
(1)
Each
layer of the filtration system of TriMask shall be placed and clamped between
the 6-level Andersen sampler and aerosol chamber. The layer with the lowest value
of BFE would be the value of BFE for the TriMask per se.
(2)
An
aerosolized bacteria, staphylococcus aureus, is flushed through the glass channel
towards Trimask.
(3)
The
numbers of colonies formed in the agar plates would be quantified to the BFE using
equation 3.
(4)
Compare
the calculated BFE to the data from ASTM.
Differential
Pressure test
The differential pressure (ΔP) pertains to the restriction of the face mask to airflow passing through it, basically the breathability of the mask (Berkshire Corporation, 2020). This test is accompanied by a manometer or a specific instrument at a constant airflow rate and is performed by measuring the air pressure differences on both sides of the specimen (Chua, 2020). It is shown in equation 4 where Ps indicates the pressure in the surrounding, Pm indicates the pressure inside the mask, and SA indicates the surface area of the face mask. ASTM mentioned that a value of ΔP less than 5.0 provides a high barrier mask. The greater the differential pressure, the harder it is to breathe, the better protection.
The process of the differential pressure test is as follows
(Qualitest, 2021):
(1)
Using
a face mask differential pressure tester, situate the facemask on the filter
holder.
(2)
Interact
with the screen of face mask differential pressure tester to initiate the testing
(3)
Gather
the result that is provided on the screen of face mask differential pressure tester
Fluid
Resistance test
The
fluid resistance of the masks pertains to the strength of hydrophobicity of the
plant-based wax located on the outermost layer of the TriMask. This assesses
the performance of the mask in terms of acting as a barrier to respiratory droplets
from its outer layer to its inner layer. This test is performed in accordance to
ASTM F1862 standard (Chua, 2020), where a sample of blood is omitted against the outer surface of the
face mask at different velocities. ASTM F1862 suggests three protection levels that
correspond to the fluid resistance, as shown in Table 1. To determine the success
of the test, a trace of the sample should not be evident on the inner layer of
the face mask (Chua, 2020); otherwise, the procedure failed.
|
Table 1. ASTM F2100-11 levels |
||
|
Level |
Protection |
Fluid Pressure (mmHg) |
|
1 |
Low barrier |
80 |
|
2 |
Medium Barrier |
120 |
|
3 |
High Barrier |
160 |
The process of the fluid resistance
tests are, as follows (Songer, 2020):
(1)
Separately
spray a synthetic blood against the TriMask at different pressure levels (i.e.,
80 mmHg, 120 mmHg, and 160 mm Hg).
(2)
Observe
if blood is evident in the inner layer of TriMask.
(3) Use Table 1 to classify TriMask.
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