Patent Publication Number: US-9839938-B2

Title: Device for carrying out a deposit of particles on a substrate and deposition method using such a device

Description:
The invention relates to the field of distributing particles on a surface. The invention particularly relates to a depositing device for particles via the liquid route or a device for depositing particles via the liquid route. The invention further relates to a method for depositing particles via the liquid route. Finally, the invention relates to a product obtained by the method according to the invention. 
     It is known to deposit on a surface particles in suspension in a liquid. It is possible to deposit some liquid on the surface then to evaporate the liquid. 
     However, it is complex to deposit particles on surfaces in a repeatable manner according to this method. This is because the quantity of particles deposited depends on the method of depositing the liquid. In order to control this quantity, it is necessary to deposit a calibrated volume of this liquid in order always to have the same quantity of material available in order to fill structures of a structured substrate with the particles. 
     When the volumes of liquid to be deposited are small and when the sizes become small, phenomena of capillarity become dominant and complicate matters. 
     An object of the invention is to provide a device for depositing particles via the liquid route, improving the devices known from the prior art. In particular, the invention proposes a simple device which allows operations for depositing particles via the liquid route which are repeatable, reliable and precise. 
     According to the invention, the device for depositing particles via the liquid route comprises:
         a first chamber,   a second chamber,   a communication hole between the first chamber and the second chamber and   a vent which is provided in the second chamber and which places the second chamber and a medium which is external with respect to the device in communication.       

     The vent and the communication hole may be arranged opposite each other in the second chamber or substantially opposite each other in the second chamber and/or the vent and the communication hole may be arranged on two opposing or substantially opposing walls of the second chamber. 
     The first chamber and the second chamber may have a first wall and a second wall which are arranged one in continuation of the other, respectively. The first chamber and the second chamber may have in particular a common ceiling. 
     The first chamber may be parallelepipedal or substantially parallelepipedal and/or the second chamber may be parallelepipedal or substantially parallelepipedal. 
     The volume of the first chamber may be less than the volume of the second chamber, or the volume of the first chamber may be less than half of the volume of the second chamber, or the volume of the first chamber may be less than one-third of the volume of the second chamber. 
     The height of the first chamber may be less than the height of the second chamber, or the height of the first chamber may be less than half of the height of the second chamber, or the height of the first chamber may be less than one-third of the height of the second chamber. 
     The device may comprise a base and a cover which is removable and/or fitted to the base. 
     The device may be produced from a silicone-based material, in particular PDMS. 
     The volume of the first chamber may be approximately from 30 to 40 mm 3  and/or the volume of the second chamber may be approximately 100 mm 3 . 
     According to the invention, the method for depositing particles on a surface of a substrate comprises the use of a device defined above. 
     The method may comprise the following steps,
         positioning the device on the surface of the substrate;   supplying the first chamber with a liquid charged with particles, in particular through a wall of the first chamber;   evaporating the liquid.       

     The step of supplying the first chamber with a liquid charged with particles may be carried out by means of a tool, in particular a needle, the end diameter of which is less than the height of the first chamber. 
     The invention also relates to a product obtained by carrying out the method defined above. 
    
    
     
       The invention will be better understood from a reading of the following description given purely by way of example and with reference to the appended drawings, in which: 
         FIG. 1  is an exploded perspective view of a first embodiment of the device according to the invention. 
         FIG. 2  is a top view of the base of the device according to the first embodiment, the dimensions being indicated in mm. 
         FIG. 3  is a cross-section taken along the plane III-III of the base of the device according to the first embodiment. 
         FIG. 4  is a top view of the device according to a second embodiment of the invention. 
         FIG. 5  is a cross-section of the device according to the second embodiment. 
         FIG. 6  is a cross-section of the device according to the second embodiment, the device being used in order to carry out a first step of carrying out a deposition method according to the invention. 
         FIG. 7  is a cross-section of the device according to the second embodiment, the device being used to carry out a second step of carrying out a deposition method according to the invention. 
     
    
    
     A first embodiment of a device  10  for depositing particles via the liquid route according to the invention is described below with reference to  FIGS. 1 to 3 . A second embodiment of a device  10  for depositing particles via the liquid route according to the invention is described below with reference to  FIGS. 4 and 5 . The two embodiments differ from each other only as a result of dimensional characteristics and the presence of a cover  2  which is removable or fitted to a base  1  in the first embodiment, or a cover either being fixed to the base or being monobloc with respect to the base in the second embodiment. 
     The device  10  comprises:
         a first chamber  11 ,   a second chamber  12 ,   a communication hole  13  or channel or passage between the first chamber  11  and the second chamber  12  and   a vent  14  which is provided in the second chamber and which places the second chamber and a medium  200  which is external with respect to the device in communication.       

     The external medium is the ambient atmosphere, in particular ambient air. The vent is arranged in a vertical wall of the second chamber which is not intended to come into contact with a liquid which will be injected into the chambers. 
     The first and second chambers which are connected via the communication hole therefore form a single cavity. 
     The communication hole may not have a cross-section having a surface-area smaller than the one which the chamber having smaller dimensions has, at least in the region of the hole. 
     As set out above, the first chamber and the second chamber are constructed in the device, in particular in the base  1 . The cover  2  closes the first chamber and the second chamber at one side of the device. At the other side of the device, the second chamber has an opening  129  which is intended to be closed by a surface  101  of a substrate which is intended to be processed as described below, that is to say, a surface on which particles have to be deposited. The first chamber and the second chamber advantageously have a first cover wall  111  and a second wall  121  which are arranged one in continuation of the other, respectively. In this manner, the cover may form a ceiling  111 ,  121  common to the first chamber and the second chamber. 
     Preferably, the vent and the communication hole are arranged opposite each other in the second chamber or substantially opposite each other in the second chamber. In particular, the vent and the communication hole may be arranged on two opposing or substantially opposing walls  122 ,  125  of the second chamber, in particular walls which are parallel or substantially parallel. The advantage of such an arrangement or configuration will be set out below. 
     For example, the first chamber is parallelepipedal or substantially parallelepipedal and/or the second chamber is parallelepipedal or substantially parallelepipedal. For example, the first chamber has a bottom  119  and lateral walls  113 ,  114  and  115 . For example, the second chamber has lateral walls  122 ,  123 ,  124  and  125 . 
     The volume of the first chamber is less than the volume of the second chamber. The volume of the first chamber may in particular be less than half of the volume of the second chamber, or the volume of the first chamber may be less than one-third of the volume of the second chamber. In particular, the volume of the first chamber is approximately from 30 to 40 mm 3  and/or the volume of the second chamber is approximately 100 mm 3 . With the dimensions of the chambers of the device of  FIG. 3 , the volume of the first chamber is 36 mm 3  and the volume of the second chamber is 108 mm 3 . It is evident that larger volumes may be implemented using chambers which cover surface-areas which may be up to several hundreds of cm 3  and on which particles have to be deposited. 
     The height h′ of the first chamber is preferably less than the height h of the second chamber, or the height h′ of the first chamber is less than half of the height h of the second chamber, or the height h′ of the first chamber is less than one-third of the height h of the second chamber. For example, h is 3 mm and h′ is between 0.5 mm and 1.5 mm, in particular 1 mm. 
     The second chamber is connected to the first chamber via the hole  13 , having a cross-sectional surface-area which is one-third of the surface-area of a side of the second chamber, to which the first chamber is connected. The first chamber may have the same width as the second chamber and/or the upper walls  111 ,  121  thereof may be co-planar. 
     The device is preferably produced from a silicone-based material, in particular PDMS (or polydimethylsiloxane). The horizontal faces, that is to say, the cover, may be produced from glass. 
     The device may be produced, for example, by moulding PDMS in an aluminium mould. Other materials may be used but the wettability of those materials by the liquid used must be similar to that of the PDMS by water. 
     One manner of carrying out a method for depositing particles on a surface  101  of a substrate  100  is described below with reference to  FIGS. 6 and 7 . 
     The method comprises the use of a device as defined or described above. 
     The deposition method comprises the following steps,
         positioning the device  10  on the surface  101  of the substrate  100 , as illustrated in  FIG. 6 ;   supplying the first chamber  11  with a liquid  30  charged with particles, in particular through a wall  111  of the first chamber, as illustrated in  FIG. 6 ;   evaporating the liquid, as illustrated in  FIG. 7 .       

     The step of supplying the first chamber  11  with a liquid  30  charged with particles is carried out by means of a tool  110 , in particular a needle, the diameter of the end of which is advantageously less than the height h′ of the first chamber  11 . 
     Once the device has been positioned on the surface of the substrate on which the particles have to be deposited, it is first necessary to fill the first chamber, then the filling action is continued in the second chamber, the liquid introduced into the first chamber travelling towards the second chamber via the hole  13 . That filling is carried out by means of a tool which allows piercing of a wall of the first chamber, in particular the wall  111  or the wall  115 . The filling is continued until coverage is provided of the surface  101  of the substrate on which particles have to be deposited and is stopped before the second chamber is completely filled, that is to say, before the wall  122  having the vent  14  is wetted. Therefore, the measure of liquid contained in the tool must be calibrated and less than the volume of the cavity formed by the first and second chambers. As a result of the phenomena of capillarity, the liquid progressively wets the walls  125 ,  101 ,  121 ,  123  and  124  during the filling action after being discharged via the hole  13  and the liquid front  31  progresses towards the wall  122 , discharging the gas, in particular the air contained in the second chamber, via the vent  14 . 
     As a result of the configuration of the device, it is impossible to impose wetting conditions on the liquid before it is introduced into the second chamber. The first chamber must be completely filled (or substantially filled; there may remain one or more air pockets) before the start of the filling of the second chamber. Therefore, the liquid will be distributed in the second chamber from the communication hole  13  and therefore only progressively wetting the surfaces of the second chamber, for example, progressively wetting five of the walls of the second chamber. The wall  122  having the vent  14  faces the liquid front but is not reached by the liquid, the volume of liquid being established or calibrated in order to prevent it from wetting that wall. The liquid front  31  may thus be formed substantially parallel with the wall  122 . That effect is obtained by the arrangements relating to the vent and the communication hole in the second chamber. The vent and hole are, for example, arranged opposite each other or substantially opposite each other in the second chamber. 
     The first chamber may be filled without any constraint on the position of the tool  110  ensuring the filling operation, in particular the needle  110 . The diameter of the end of the tool  110  is, for example, 0.5 mm. This tool allows the material of the device to be pierced in order to inject the liquid. The effect obtained is independent of the position of the injection. This is because, during the injection, the end of the tool may be perpendicular to the bottom  119  of the device. Alternatively, the end of the tool may be parallel with the bottom  119  of the device. The end of the tool may further occupy any intermediate configuration. 
     In order to promote or to allow the evaporation of the liquid as illustrated in  FIG. 7 , it is possible to carry out heating, in particular heating of the substrate  100  and/or of the device  10 . During the evaporation, the liquid front  31  is moved towards the wall  125 , the evaporation gas of the liquid being discharged via the vent  14 . During discharge, the liquid front leaves on the walls and on the surface  101  of the substrate, in particular in structures or impressions  102  which are formed in the surface  101 , a deposit  103  of particles which were previously in suspension in the liquid. In accordance with the density of particles in the liquid and in accordance with the shape and/or size of the structures, it is thereby possible to deposit the number of particles which is desired in each structure. 
     The vent can be coupled to an aspiration system. The control of the aspiration system may improve, in a state associated with the heating, the efficacy of the deposit of particles. 
     If particles have to be deposited on a large substrate surface, and if the cavity has a large volume, the device may comprise a plurality of vents. The vents are preferably distributed over the wall  125 . It is also possible to dispense with the wall  125 . The opening of the second chamber in this region constitutes a vent having large dimensions. 
     The device  10  may subsequently be withdrawn or removed. In other words, the device  10  may be removed or separated from the substrate. Thus, a product  100  or a substrate  100  produced by carrying out the method defined or described above is obtained. Therefore, a product  100  or a substrate  100  on which particles have been deposited is obtained. 
     As a result of the solution described above, it is possible to bring about an introduction of the tool which supplies the liquid which does not destroy or damage the substrate. When the desired quantity of liquid is established, the operation becomes reproducible because the quantity deposited will always be identical. 
     When a liquid is injected into a cell whose volume is similar to the volume of the injected liquid, it is very difficult to be deterministic regarding the faces which will be in contact with the liquid. As a result of the solution described above, it is thus possible to inject a liquid into a closed volume, for example, of parallelepipedal form, with a tool in a deterministic manner. The filling is reproducible and independent of the dexterity of the operator. It is known that only some predetermined walls of the second chamber will be wetted by the liquid. Finally, as a result of the geometry of the device, it is possible not to damage the walls of the second chamber or the surface of the substrate (by puncturing the wall or the surface). 
     Depositing particles on a surface may allow the subsequent analysis of the particles and/or the characterisation thereof. Depositing particles on a surface may allow a functionalisation of the surface, wherein the particles fulfil a predetermined function, in particular a function which they fulfil intrinsically. 
     In this document, the term “vent” is intended to be understood to be any opening or passage or any assembly of openings or passages allowing gas to be discharged.