While the ongoing outbreak of 2019-2020 severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2, previously known as 2019-nCoV) gains significant prevalence worldwide, scavenging a curative remedy has become the main thrust to all scientists across the globe. Alike personal protective equipment (PPE), usage of homemade do-it-yourself (DIY) cloth mask has attracted global attention to combat novel coronavirus. Though the performance of various fabrics used in such a homemade mask is still under observation, their response is likely to be anticipated for combatting severe respiratory issues caused by the novel pandemics. In regards to the present scenario, the recent report by Konda et al. illustrated the filtration efficiency of differently combined fabrics depends on the particle size of aerosol, and its found to be promising for the wide bracketed size (10 nm-6µm) particles. Their study unveils aerosol filter made by the combination of chiffon and silk that are significantly efficient. 1 Therefore, a hybrid combination of non-woven fabrics having different threads count per unit shows effective filtration efficiency fornanosize particles. Improper and loose-fitting might prevent the working of that mask as the filtration is based on the principle of static electricity. Kutter et al. have well demonstrated the variation in the size of respiratory droplet, which are well known as aerosols (<5 µm) and droplets (>5 µm). 2 Among these, water droplets and liquefied gas droplets come into play as a medium on which SARS-CoV-2 can traverse over a long distance when the size is relatively small,. Otherwise, larger droplets can settle down easily without traveling a large distance.
Based on the available knowledge of various aspects of infection spread by SARS-CoV-2 virus, the initialspreading is likely to be spread by direct contact, or by providing a transmission path to land the large virus-containing droplets, 3 which are found to remain stable for more than 24 hrs. 4 COVID positive patients can also passively spread viruses to the people surrounding them. As per the underlying precaution made by WHO 2020a, wearing a face mask is mandatory to combat COVID-19. 5 Another route of transmission might be of either only in passing or by traversingvirus contained aerosols. So in that case, the liquefied dropletsstart to evaporate immediately after the expiry of droplets and, someofthe smaller sized dropletstransported by air discharge field rather than gravitation. Such small virus-loaded droplets get enough liberation to traverse in the air several meters from their route. 6 Following five basic steps of aerosol filtration, the electrostatic attraction takes predominant role alike gravity sedimentation, inertial impaction, interception, and diffusion. [7] [8] All these mechanisms are solely size-dependent, i.e. gravitational forces come into play for larger sized droplets (> 1µm), whereas sedimentation and impaction are only applicable for medium-sized particles (> 1µm to 10µm). Lesser the size of the particles (100 nm-11µm), higher will be the tendency of those particles to get diffused by mechanical interception, and Brownian motion.Interestingly, nanosized particles can easily slide between the opening network of non-woven fibers. 9 In such cases, electrostatic attraction (EA) takes significance to bind and cling such particles to the fibers. The newly invented principle of fusing EA with nanogenerators capable of generating triboelectric charges from the wasted mechanical energy from our daily activities (respiration, talking, or any other facial movement) can be utilized favorably in mask design, 10 which has been conceptualized in the present study.
In this context, we present the design and simulation of a novel self-powered triboelectric nanogenerator (TENG) fused smart mask, in which the viruses are killed in the electric field and the wearer can combat the deadly novel coronavirus. Recent findings on the use of cloth mask during the outbreak of Influenza in 2009 appeared to be inadequate to conclude the selection of fabrics having significant filtration efficiency. [11] [12] Though the recent study by Konda et al. have envisaged that the thread counts of respective non-woven fiber play a key role in electrostatic filtration, but does not guarantee for the case of inhaling viral particles coming from the environment.
The proposed face mask is composed of multilayers, out of which inner and middle layers comprise of tribo-series materials (TSM). The prototype design of the self-powered smart mask is shown in Figure 1 (a). Since TENGs exhibit quadratic relation between power density, and triboelectric charge density, increasing the tribo-charges is a challenging issue. [13] [14] [15] [16] That can be done using structural optimization of different tribo-series materials, surface modification, etc. 17 Interestingly, nucleocapsid protein crowned SARS-CoV-2 possesses surface electrostatic potential characteristics, that reinforced the present design concept. 18 Keeping all these in mind, five combinations of readily available non-woven TSM have been chosen, each with a pair of positive TSM and negative TSM followed by a self-powered smart layer. As a good energy harvester, vocal energy exerted during talking, or any other lip activities have been utilized as the prime source of power to induce static electricity in between the inner and middle layers of the proposed mask.
The detailed characteristics of the five pairs of TSM are illustrated in the next section. The selfpowered induced potential allows the thin metal framing of these layers to transfer charges between them. The layer is capable of acquiringthe static charges so that any viral particle having surface charge can easily be inactivated in the outer layer. 19 The activated outer or smart layer can adhere electrically the charged viral particles coming from the close vicinity of the wearer. The novelty of this design lies in the self-activation of the smart layer through the vocal activities of the wearer and has provision to deal with aerosols as well as droplets (gaseous, liquid). The essence of the proposed multilayer self-powered smart mask is low-cost, comfortable texture,and wide accessibility thatassures no internal respiratory problem (breathing problem) to the wearer. In this paper, the simple mechanism of auto harvesting energy, contact electrification, and electrostatic induction enabled TENG have been utilized. The comparative study of reported design face mask is explained in Table 2 . The corresponding features of triboseries fabrics belonging to the positive and negative series of the tribo-series is described in Table 1 . To boost up the output charge of TENG, combination of nylon -polyester, cotton -polyester, PMMA -PVDF, lylon -PVDF and polypropylene -polyester have been studied. Based on this, the electrostatic simulation has been carried out.
The principle of TENGs isfusion of contact electrification and electrostatic induction. Static polarized charges are mainly induced through contact electrification which further triggers the energy conversation from self-harvested vocal energy to electrical energy through electrostatic induction.
Initially, the separation distance ( ) between two tribo-pairs can be varied according to the activity of the liops of the wearer. The mechanical force exerted by the lip activity makes them come in contact with each other. The material in each tribo-pairs share opposite tribo-charges as aresult of contact electrification. The insulated construction of each layer (Figure 1 b) , confirms that the charges can only transfer between tribo-layers (TL) through external circuits. If '+ ' denotes the transferred charges between TLs, one TL will acquire transferred chargeand the other TL will have the transferred charge of + . In Figure 2A , the separation distance between the TLs is ' ' with an area of ' '. We consider the size of the virus-loaded particle to be 1µm. The electrical potential difference between the TLs of TENG is supposed to contribute two major components.
The induced polarized TE generates charges and voltage , which is a function of ' '. Considering the induced voltage to be 1V, the outgoing viral particles will be under very high electric field (E), i.e. 10 6 V/m, as calculated using equation 1.
(1) Therefore, the generated higher electric field is capable enough to make a contact between these TLs, since the air discharge field is 3×10 6 V/m. The other perspective illuminates that the viral respiratory droplets are of conducting nature, hence their resistance will be smaller (1kΩ). Also, 1mA current through the human body is sufficient enough to inactivate the surface charge of the virus. Therefore, the two TLs of 1µm apart with selfgenerated voltage in the mask is around 1 V, that indicates the aerosolized droplet can easily be burnt through short-circuiting in the third smart layer. If the test droplet does not contain critical amount of surface charge, then also water particles make the layer shorted.
It's imperative to measure the safety of the wearer concerning the generated heat energy,illustrate this, four holes (p, q, r, s) are considered in the front side, whereas the hole in the opposite side the respected layer is depicted by 'A' (Figure 2B) . The tendency of the incoming droplets entering through any of the holes (p, q, r, s) to emanate through the hole 'A' in the opposite side of the layer. During the passage from TLs to the smart layer, the droplet has to adhere to the mesh of the smart layer that has already been energized highly. Therefore, the high field induced in the smart layer capable of electrocuting the outgoing droplet by heat burning. The produced heat would be in the order of 1fJ/µm 3 /ºk (considering the air specific density ̴ 1kJ/m 3 /ºk). This phenomenon further assures the heat energy produced to electrocute the outgoing particles would not create much heat to initiate any breathing problems to the wearer.
It has been illustrated in phase of the wearer. Therefore, the effect of a variation in inspiration and expiration times subjected to a pressure difference of 1kPa ( Supplementary Information, Note S1 ).
Since the novelty of the proposed mask lies in the smart layer, the utilization of the developed charged between TLs should be sufficient to allow electrocution in the smart layer.
In order to analyze the charge density of two TLs based TENG, average energy available from breathing can be calculated as 5 10 5 × J (considering ~ 5 mm), as shown in Figure 3 . Table 1 is illustrating the TECD of nylon -polyester, cotton -polyester, PMMA -PVDF, nylon -PVDF, and polypropylene -polyester. It can be understood from Table 1 Table 2 . Synthetic polymer (polyolyfin fiber) and electret treated nonwoven web (meltbown web) (i) It has designed to work using the principle of telephone handset.
(ii) The non-woven web is coated with a pressure sensitive adhesive so that the sound energy travels through the air into the microphone and makes the layer vibrate and respective layer converts the sound into electricity to make the outer layer electret so that incoming viral particle can be killed. Internal and external spunbonded non-woven fabric, felt type tribocharged nonwoven fabrics, a ply of meltblown microfibre (i) First intermediate layer of felt-type tribo-charged nonwoven fabric based on at least two differenttypes of fibres suitable for giving the fabric opposite electric charges that enhance the filtration.
(ii) The mask can filtrate particle sizes in the range of submicron.
Electrically charged filter and mask 23 Four layered comprises of three layered liquid charged non-woven fibers and one layered tribocharged nonwoven fabric.
(i) The induced temperature due to liquid charge intensity likely to b e less than 40⁰ C, which is insufficient to combat novel corona virus.
(ii) Refilling of polar liquid in the liquid charged fabric might be troublesome as it requires immersion apparatus alike spraying in the form of droplets, mist, shower etc.
Non-woven film and charged nonwoven biological protection mask 24 The inner layer made of rare earth material 'zein' and positive chitosan based outer layer.
(i) The mask basically deals with biological protection, and particularly relates to a nonwoven film and a charged nonwoven biological protection mask.
(ii) A charged 'zein' based nanofiber double-layer film prepared through an electrospinning technique can isolate virus through the dual functions of electrical charge absorption and mechanical isolation.
Sheet material composed of a resin fiber with wounding of copper wire.
(i) A copper wounded woven fiber sheet has been used for initiating corona discharge, i.e. the viral particles comes in close vicinity of the mask filter.
(ii) It is mentioned the mask is so designed to provide bactericidal effect unlike virucidal effect.
Mask using frictional and static electricity 26 Polymer, nylon, cotton, silicon based polymer, polypropylene (PE), polypropylene terephthalate (PET) (i) The design works based on the electrostatic and triboelectric properties.
(ii) The mask is its location specific, based on the country specific weather conditions (fine and yellow dust) the structure of the mask has been designed and it cannot be reusable.
Medical protective breathing mask 27 The multylayer made of chitin fiber or silk fiber, hydrophilicandfwovenchemical fiber fabrics.
(i) The outgoing gas is transferred to the environment through the adsorption -diffusion-desorption process of the hydrophilic group of the functional film.
(ii) . The embodiment of the developed mask is pretty promising, but the working mechanism of such fiber including the contribution of chemicals involved here is quite ambiguous.
Respiratory protection mask 28 Non-woven of melt-blown type fibers (i) respiratory protection mask with greater breathability and to reduce breathing resistance.
(ii) The mask is intended to retain solid or liquid particles suspended in the air and in particular viruses or bacteria capable of causing diseases such as influenza.
Masks that use electrostatics of materials to protect healthy individuals from COVID 19 29 Nylon cloth sandwiched between polypropylene layers (i)The mask usable to adsorb viral particles between layers produced static electricity.
(ii) High chance to cross the electrostatic barrier as clinging on the surface of electrostatic layers requires a low pressure drop of incoming breathe. (ii) The enhanced performance of the hybrids is likely due to the combined effect of mechanical and electrostatic-based filtration.
Nylon-polyester, cottonpolyester, PMMA -PVDF, nylon -PVDF, , polypropylene-polyester (i) Design of the self-powered marks confirms the capability of the mask to function in response to talking, signing or any gestures of lips of the wearer with no difficulties of fetching external power source.
(ii) Tribo-series fabricsgenerates of static electricity and charged produced due static electricity further powers up the smart layer.
(iv) The smart layer is active during inhaling and exhaling period of wearing of the mask, which can be achieved by the capacitance connected with the electronic converter.
(v) Any virus-consist droplets/ aerosols can get electrified in the smart layer and furtherany virus get deactivated underthe tribo-field. (vi) The proposed self-powered marks can generate thermal power in the range of 0.4W per second which is more than enough to electrocute virus-loaded aerosols.
(vii) Proposed mask is designed with simple elastic band for easy usage for every person including child.
While the whole world has been suffering from the devastating COVID-19, safety precausion becomes a key concern to live life in the adverse situation. The present report illustrates the design of three-layered TENG based facial mask. The different combination of TSMs have been experimented in order to get better filtration efficiency in terms of TECD. The combination of easily available cotton and polyester fabric can be utilized in designing self-powered smart mask based on its highest TECD and induced power (0.38W per second). The study has also brought light into the voltage-current-power generated by the contact electrification of the TLs. The prototype mask can be activated through breathing cycles (and/or talking or other relevant facial gesture) without the need of any external power source. The accumulated charge can powered the smart layer upto 0.38 W which is sufficient enough to destroy the viral particles possibly by electrocution. The present design of facial mask can preferably reach the breakthrough in terms of
Note S1:
Work done by exhaling is given by dw = P.dv (assuming pressure inside the plates to be constant) and, dv = A.dx
Where, A = Active area.  Maximum pressure change during one breathing cycle =100 mm of water  Normal air pressure=760 mm of Hg = 1.01325 bar Therefore, pressure variation during breathing is 1kPa.