fig1 illustrates a microfluidic delivery system 10 in accordance with one embodiment of the disclosure . the microfluidic delivery system 10 includes a housing 12 having an upper surface 14 , a lower surface 16 , and a body portion 18 between the upper and lower surfaces . the upper surface of the housing 12 includes a first hole 20 that places an environment external to the housing 12 in fluid communication with an interior portion 22 of the housing 12 . the interior portion 22 of the housing 12 includes a holder member 24 that holds a removable microfluidic refill cartridge 26 . as will be explained below , the microfluidic delivery system 10 is configured to use thermal energy to deliver fluid from within the microfluidic refill cartridge 26 to an environment external to the housing 12 . access to the interior portion 22 of the housing is provided by an opening 28 in the body portion 18 of the housing 12 . the opening 28 is accessible by a cover or door 30 of the housing 12 . in the illustrated embodiment , the door 30 rotates to provide access to the opening 28 . although the opening and door are located on the body portion of the housing , it is to be appreciated that the opening and door may also be located on the upper surface and the lower surface of the housing . furthermore , it is to be appreciated that in other embodiments , the housing has two or more separable parts for providing access to the interior portion . the holder member 24 includes an upper surface 32 and a lower surface 34 that are coupled together by one or more sidewalls 36 and has an open side 38 through which the microfluidic refill cartridge 26 can slide in and out . the upper surface 32 of the holder member includes an opening 40 that is aligned with the first hole 20 of the housing 12 . the holder member 24 holds the microfluidic refill cartridge 26 in position when located therein . in one embodiment , the holder member 24 elastically deforms , thereby gripping the microfluidic refill cartridge 26 in place when located in the holder member . in another embodiment , the holder member 24 includes a locking system ( not shown ) for holding the microfluidic refill cartridge in place . in one embodiment , the locking system includes a rotatable bar that extends across the open side of the holder member to hold the microfluidic refill cartridge in place . the housing 12 includes conductive elements ( not shown ) that couple electrical components throughout the system as is well known in the art . the housing 12 may further include connection elements for coupling to an external or internal power source . the connection elements may be a plug configured to be plugged into an electrical outlet or battery terminals . the housing 12 may include a power switch 42 on a front of the housing 12 . fig2 a shows the microfluidic refill cartridge 26 in the holder member 24 without the housing 12 , and fig2 b shows the microfluidic refill cartridge 26 removed from the holder member 24 . a circuit board 44 is coupled to the upper surface 32 of the holder member by a screw 46 . as will be explained in more detail below , the circuit board 44 includes electrical contacts 48 ( fig3 ) that electrically couple to contacts of the microfluidic refill cartridge 26 when the cartridge is placed in the holder member . the electrical contacts 48 of the circuit board 44 are in electrical communication with the conductive elements . fig3 is a cross - section view of the microfluidic refill cartridge 26 in the holder member 24 along the line 3 - 3 shown in fig2 a . with reference to fig2 b and fig3 , the microfluidic refill cartridge 26 includes a reservoir 50 for holding a fluid 52 . the reservoir 50 may be any shape , size , or material configured to hold any number of different types of fluid . the fluid held in the reservoir may be any liquid composition . in one embodiment , the fluid is an oil , such as a scented oil . in another embodiment , the fluid is water . it may also be alcohol , a perfume , a biological material , a polymer for 3 - d printing , or other fluid . a lid 54 , having an inner surface 56 and an outer surface 58 , is secured to an upper portion 60 of the reservoir 50 to cover the reservoir 50 . the lid 54 may be secured to the reservoir in a variety of ways known in the art . in some embodiments , the lid 54 is releasably secured to the reservoir 50 . for instance , the lid 54 and the upper portion 60 of the reservoir 50 may have corresponding threads , or the lid 54 may snap onto the upper portion 60 of the reservoir 54 . between the lid 54 and the reservoir 50 there may be an o - ring 62 for forming a seal therebetween . the seal may prevent fluid from flowing therethrough as well as prevent evaporation of the fluid to an external environment . a microfluidic delivery member 64 is secured to an upper surface 66 of the lid 54 of the microfluidic refill cartridge 26 as is best shown in fig2 b . the microfluidic delivery member 64 includes an upper surface 68 and a lower surface 70 ( see also fig4 ). a first end 72 of the upper surface 68 includes electrical contacts 74 for coupling with the electrical contacts 48 of the circuit board 44 when placed in the holder member 24 . as will be explained in more detail below , a second end 76 of the microfluidic delivery member 64 includes a fluid path for delivering fluid therethrough . in reference to fig3 , inside the reservoir 50 is a fluid transport member 80 that has a first end 82 in the fluid 52 in the reservoir and a second end 84 that is above the fluid 52 . the fluid 52 travels from the first end 82 of the fluid transport member 80 to the second end 84 by capillary action . in that regard , the fluid transport member 80 includes one or more porous materials that allow the fluid to flow by capillary action . the construction of the fluid transport member 80 permits fluid to travel through the fluid transport member 80 against gravity . fluid can travel by wicking , diffusion , suction , siphon , vacuum , or other mechanism . the second end 84 of the transport member is located below the microfluidic delivery member 64 . the fluid transport member 80 delivers fluid 52 from the reservoir 50 toward the microfluidic delivery member 64 . as best shown in fig4 , the second end 84 of the fluid transport member 80 is surrounded by a transport cover 86 that extends from the inner surface of the lid 54 . the second end 84 of the fluid transport member 80 and the transport cover 86 form a chamber 88 . the chamber 88 may be substantially sealed between the transport cover 86 and the second end 84 of the fluid transport member 80 to prevent air from the reservoir 50 from entering the chamber 88 . above the chamber 88 is a first through hole 90 in the lid 54 that fluidly couples the chamber 88 above the second end 84 of the fluid transport member 80 to a second through hole 78 of the microfluidic delivery member 64 . the microfluidic delivery member 64 is secured to the lid 54 above the first through hole 90 of the lid 54 and receives fluid therefrom . in some embodiments , the fluid transport member 80 includes a polymer ; non - limiting examples include polyethylene ( pe ), including ultra - high molecular weight polyethylene ( uhmw ), polyethylene terephthalate ( pet ), polypropylene ( pp ), nylon 6 ( n6 ), polyester fibers , ethyl vinyl acetate , polyvinylidene fluoride ( pvdf ), and polyethersulfone ( pes ), polytetrafluroethylene ( ptfe ). the fluid transport member 80 may be in the form of woven fibers or sintered beads . it is also to be appreciated that the fluid transport member of the present disclosure is of smaller size than is typically used for fluid transport members for refillable cartridges . as shown in fig4 , the fluid transport member 80 may include an outer sleeve 85 that surrounds radial surfaces of the fluid transport member 80 along at least a portion of its length while keeping the first and second ends 82 , 84 of the fluid transport members 80 exposed . the sleeve 85 may be made from a non - porous material or a material that is less porous than the fluid transport member 80 . in that regard , the sleeve 85 may prevent or at least reduce air in the reservoir from entering the fluid transport member 80 by radial flow . the outer sleeve 85 may be a material that is wrapped around the fluid transport member 80 . in other embodiments , the material 85 is formed on the fluid transport member 80 in an initial liquid state that dries or sets on the fluid transport member . for instance , the material may be sprayed on the fluid transport member or the fluid transport member may be dipped into a liquid material that dries . the outer sleeve may be a polymer sheet , a teflon tape , a thin plastic layer , or the like . teflon tape has particular benefits since it provides a fluid - tight seal , is flexible to wrap , is strong , and also makes it easy to slip member 80 into place . the fluid transport member 80 may be any shape that is able to deliver fluid 52 from the reservoir 50 to the microfluidic delivery member 64 . although the fluid transport member 80 of the illustrated embodiment has a width dimension , such as diameter , that is significantly smaller than the reservoir , it is to be appreciated that the diameter of the fluid transport member 80 may be larger and in one embodiment substantially fills the reservoir 50 . fig5 a and 5b , respectively , are top and bottom views of the microfluidic delivery member 64 in accordance with one embodiment . fig5 c illustrates the microfluidic delivery member 64 in exploded view . the microfluidic delivery member 64 includes a rigid planar circuit board , which can be a printed circuit board ( pcb ) 106 having the upper and lower surfaces 68 , 70 . the pcb 106 includes one or more layers of insulative and conductive materials as is well known in the art . in one embodiment , the circuit board includes fr4 , a composite material composed of woven fiberglass cloth with an epoxy resin binder that is flame resistant . in other embodiments , the circuit board includes ceramic , glass or plastic . the upper surface 68 of the second end 76 of the printed circuit board 106 includes a semiconductor die 92 above the second through hole 78 and leads 112 located proximate the die 92 . electrical contacts 74 at the first end 72 of the microfluidic delivery member 64 are coupled to one or more of the leads 112 at the second end 76 by electrical traces ( not shown ). the upper and lower surfaces 68 , 70 of the pcb 106 may be covered with a solder mask 124 as shown in the cross - section view of fig4 . openings in the solder mask 124 may be provided where the leads 112 are positioned on the circuit board or at the first end 72 where the electrical contacts 74 are formed . the solder mask 124 may be used as a protective layer to cover electrical traces . the die 92 is secured to the upper surface 68 of the printed circuit board 106 by any adhesive material 104 configured to hold the semiconductor die to the pcb . the adhesive material may be an adhesive material that does not readily dissolve by the fluid in the reservoir . in some embodiments , the adhesive material is activated by heat or uv . in some embodiments , a mechanical support ( not shown ) may be provided between a bottom surface 108 of the die 92 and the upper surface 68 of the printed circuit board 106 . as best shown in fig6 , the die 92 includes a plurality of bond pads 109 that are electrically coupled to one or more of the leads 112 by conductive wires 110 . that is , a first end of the conductive wires 110 is coupled to a respective bond pad 109 of the die 92 and a second end of the conductive wires 110 is coupled to a respective lead 112 . thus , the bond pads 109 of the die 92 are in electrical communication with the electrical contacts 74 of the microfluidic delivery member 64 . a molding compound or encapsulation material 116 may be provided over the conductive wires 110 , bond pads 109 , and leads 112 , while leaving a central portion 114 of the die 92 exposed . as best shown in fig4 , the die 92 includes an inlet path 94 in fluid communication with the second through hole 78 on the second end 76 of the delivery member 64 . with reference also to fig7 and 8 , which illustrate corresponding cross sections of the die of fig6 , the inlet path 94 of the die 92 is in fluid communication with a channel 126 that is in fluid communication with individual chambers 128 and nozzles 130 , forming a fluid path through the die 92 . above the chambers 128 is a nozzle plate 132 that includes the plurality of nozzles 130 . in a first embodiment , each nozzle 130 is located above a respective one of the chambers 128 and is an opening in the nozzle plate 132 that is in fluid communication with an environment outside of the microfluidic refill cartridge 26 . the die 92 may have any number of chambers 128 and nozzles 130 , including one chamber and nozzle . in the illustrated embodiment , the die 92 includes 18 chambers 128 and 18 nozzles 130 , each chamber associated with a respective nozzle . alternatively , it can have 10 nozzles and 2 chambers , one chamber providing fluid for a bank of five nozzles . it is not necessary to have a one - to - one correspondence between the chambers and nozzles . in one embodiment , the nozzle plate 132 is 12 microns thick . in some embodiments , in some embodiments , the nozzle 130 has a diameter between 20 - 30 microns . as is best shown in fig8 b , proximate each chamber 128 is a heating element 134 that is electrically coupled to and activated by an electrical signal being provided by a bond pad of the die 92 . in use , when the fluid in each of the chambers 128 is heated by the heating element 134 , the fluid vaporizes to create a bubble . the expansion that creates the bubble causes a droplet to form and eject from the nozzle 130 . other ejection elements may be used for causing fluid to be ejected from the nozzle 130 . for instance , piezoelectric elements or ultrasonic fluid ejection elements may be used to cause fluid to be ejected through the nozzles 130 as is well known in the art . each nozzle 130 is in fluid communication with the fluid in the reservoir by a fluid path that includes the first end 82 of the fluid transport member 80 , through the transport member to the second end 84 , the chamber 88 above the second end 84 of the transport member , the first through hole 90 of the lid , the second through hole 78 of the pcb , through the inlet path 94 of the die , through the channel 126 , to the chamber 128 , and out of the nozzle 130 of the die 92 . in reference again to fig4 , a filter 96 may be positioned between the chamber 88 and inlet path 94 of the die 92 . the filter 96 is configured to prevent at least some particles from passing therethrough , thereby preventing and / or reducing blockage in the fluid path , most particularly in the nozzles 130 of the die 92 . in some embodiments , the filter 96 is configured to block particles that are greater than one third of the diameter of the nozzles . the filter 96 may be any material that blocks particles from flowing therethrough and does not break apart when exposed to the fluid , which could create further particles to block the fluid path . in one embodiment , the filter 96 is a stainless steel mesh . in other embodiments , the filter 96 is a randomly weaved mesh and may comprise polypropylene or silicon . referring now to fig1 , there is provided a close up view of a portion of a microfluidic refill cartridge 26 illustrating a flow path with a filter 96 between the second end 84 of the fluid transport member 80 and the die 92 in accordance with one embodiment . the filter 96 is separated from the lower surface 70 of the microfluidic delivery member 64 proximate the second through hole 78 by a first mechanical spacer 98 . the first mechanical spacer 98 creates a gap 99 between the bottom surface 70 of the microfluidic delivery member 64 and the filter 96 proximate the through hole 78 . in that regard , the outlet of the filter 96 is greater than the diameter of the second through hole 78 and is offset therefrom so that a greater surface area of the filter 96 can filter fluid than would be provided if the filter was attached directly to the bottom surface 70 of the microfluidic delivery member 98 without the mechanical spacer 98 . it is to be appreciated that the mechanical spacer 98 allows suitable flow rates through the filter . that is , as the filter clogs up with particles , the filter will not slow down the fluid flowing therethrough . in one embodiment , the outlet of the filter is 4 mm 2 or larger and the standoff is 700 microns thick . the first mechanical spacer 98 may be a separate rigid support , a protrusion formed on the lower surface 70 of the microfluidic delivery member 64 , such as the solder mask , or adhesive material that conforms to a shape that provides an adequate distance between the filter 96 and the lower surface 70 of the microfluidic delivery member 64 . the adhesive material may be an adhesive material that does not readily dissolve by the fluid in the reservoir . in some embodiments , the adhesive material is activated by heat or uv . the adhesive material may be the same or different from the adhesive material used to secure the die to the microfluidic delivery member . it is to be appreciated that in some embodiments , the fluid transport member 80 is made from one or more materials that do not react with the fluid . thus , the fluid transport member 80 does not introduce contaminants into the fluid that could block fluid flow through the microfluidic delivery member 64 . in one embodiment , the fluid transport member 80 may replace the filter , so that a separate filter 96 is not needed . as shown in fig1 , the second through hole 78 of the microfluidic delivery member 80 may include a liner 100 that covers exposed sidewalls 102 of the pcb 106 . the liner 100 may be any material configured to protect the pcb from breaking apart , such as to prevent fibers of the pcb from separating . in that regard , the liner 100 may protect against particles from the pcb 106 entering into the fluid path and blocking the nozzles 130 . for instance , the second through hole 78 may be lined with a material that is less reactive to the fluid in the reservoir than the material of the pcb . in that regard , the pcb may be protected as the fluid passes therethrough . in one embodiment , the through hole is coated with a metal material , such as gold . prior to use , the microfluidic refill cartridge 26 may be primed to remove air from the fluid path . during priming , air in the fluid path is replaced with fluid from the reservoir 50 . in particular , fluid may be pulled up from the fluid transport member 80 to fill the chamber 88 , the first through hole 90 of the lid 54 , the second through hole 78 of the microfluidic delivery member 64 , the inlet path 94 of the die 92 , the channel 126 , and the chamber 128 . priming may be performed by applying a vacuum force through the nozzles 130 . the vacuum force is typically performed with the microfluidic refill cartridge in an upright position for a few seconds . in some embodiments , a vacuum force is applied for 30 to 60 seconds . the microfluidic refill cartridge 26 may also be primed by applying air pressure through a hole 140 ( fig9 ) in the lid 54 of the cartridge that is in fluid communication with the reservoir 50 to increase the air pressure on the fluid in the reservoir 50 , thereby pushing fluid up the fluid transport member 80 through the fluid path . it is to be appreciated that the hole is sealed with a cover 120 ( see fig2 b ), such as elastic material that fits into at least a portion of the hole , after priming . once primed , the nozzles 130 may be sealed to prevent de - priming of the fluid path . de - priming may occur when air enters the fluid path . in that regard , a cover ( not shown ) may be placed over the nozzles 130 to prevent air from outside of the microfluidic refill cartridge 26 from entering the fluid path . it is to be appreciated that in some embodiments , the outer sleeve 85 of the fluid transport member 80 may prevent de - priming of the fluid transport member 80 . that is , the sleeve 85 prevents air from entering the fluid transport member 80 along its radial surface . once primed , during use , when fluid exits the nozzle 130 , fluid from the reservoir 50 is pulled up through the fluid path by capillary action . in that regard , as fluid exits the chamber 128 , fluid automatically refills the chamber 128 by being pulled through the fluid path by capillary action . as indicated above , the transport cover 86 in combination with the second end 84 of the fluid transport member 80 form a seal that fluidly isolates the chamber 88 from the reservoir 50 to assist in keeping the microfluidic refill cartridge 26 primed . it is to be appreciated that the chamber 88 may be at a different pressure than the reservoir 50 . it is to be appreciated that in many embodiments , the fluid transport member 80 is configured to self - prime . that is , fluid may travel from the first end 82 of the fluid transport member 80 to the second end 84 without the aid of a vacuum force or air pressure as discussed above . the microfluidic refill cartridge 26 includes a vent path that places the reservoir in fluid communication with the external environment of the microfluidic refill cartridge 26 . the vent path equalizes the air pressure in the reservoir 50 with the air pressure of the external environment . that is , as fluid exits the microfluidic refill cartridge 26 through the nozzles 130 , air from the external environment fills the space in the reservoir 50 that is made by the removed fluid . in that regard , the air pressure above the fluid in the reservoir remains at atmosphere . this allows the microfluidic refill cartridge to remain primed and prevents or at least reduces back pressure in the fluid path . that is , by equalizing the pressure in the reservoir , the reservoir does not create a vacuum that pulls the fluid from the fluid path back into the reservoir . referring now to fig9 , the vent path includes a first vent hole 142 in the lid 54 of the microfluidic refill cartridge and a second vent hole 144 in the microfluidic delivery member 64 ( see fig5 a and 5b ). the first and second vent holes 142 , 144 are not aligned with each other but are in fluid communication with each other by a channel 146 formed in the upper surface 66 of the lid 54 . it is to be appreciated that in another embodiment , the lower surface 70 of the microfluidic delivery member 64 could alternatively or additionally include a channel that places the first vent hole 142 in fluid communication with the second vent hole 144 . it is to be appreciated that separating the first vent hole 142 from the second vent hole 144 by the channel 146 reduces the evaporation rate of the fluid in the reservoir 50 through the vent path . upon depletion of the fluid in the reservoir 50 , the microfluidic refill cartridge 26 may be removed from the housing 10 and replaced with another microfluidic refill cartridge 26 . alternatively , the microfluidic refill cartridge 26 may be refilled through the hole 140 in the lid 54 as best shown in fig9 . the various embodiments described above can be combined to provide further embodiments . all of the u . s . patents , u . s . patent application publications , u . s . patent applications , foreign patents , foreign patent applications and non - patent publications referred to in this specification and / or listed in the application data sheet are incorporated herein by reference , in their entirety . aspects of the embodiments can be modified , if necessary to employ concepts of the various patents , applications and publications to provide yet further embodiments . these and other changes can be made to the embodiments in light of the above - detailed description . in general , in the following claims , the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and the claims , but should be construed to include all possible embodiments along with the full scope of equivalents to which such claims are entitled . accordingly , the claims are not limited by the disclosure .