Patent Description:
Consumer and industrial inkjet printing is well known. In such applications, it is known in the application that the individual nozzles in the ejection chip should be individually addressable so that they can be actuated on demand. As the ejection head is passed over the media to be printed, an image is formed that requires a certain data rate from the control element that controls the actuation of the nozzles. This data rate may be achieved through a combination of a number of signal lines and a signaling rate where digital data are passed into the ejection chip. Together, the signal lines and signaling rate form a communications channel that must be capable of passing enough information to form the required image while the ejection head is traveling at the required speed.

A compromise must be achieved when designing a printing system where the number of signal lines is not excessive, increasing the size and complexity of the system. If the number of signal lines is small, and the communication protocol with the ejection chip is not efficient, the signaling rate into the chip can become so high that it is not possible to maintain acceptable signal integrity. The example below illustrates the choices made when designing such printing systems.

For ink-jet printing applications, the microfluidic ejection element is optimized to produce high resolution images while minimizing overall print time. For these reasons the thermal actuators (i.e., heaters) on the ejection chip will typically be arrayed to provide a half inch print swath or greater with thermal actuator to thermal actuator spacing at <NUM> (<NUM>/<NUM> inch) or <NUM> (<NUM>/<NUM> inch).

As an illustration, the nozzle placement and addressing architecture of a <NUM> (two-thirds inch), <NUM> drops per millimeter (<NUM> drops per inch) printhead with a total of <NUM> thermal actuators is described.

<FIG> shows the thermal actuator placement for this prior art example. As shown, the thermal actuators on one side of the fluid via are vertically spaced at <NUM> (<NUM>/<NUM> inch) with the thermal actuators on the opposite side also spaced at <NUM>/<NUM> inch but shifted vertically by <NUM> (<NUM>/<NUM> inch). This allows for single pass printing to place a drop of ink at each point on a <NUM> (<NUM>/<NUM> inch)vertical pitch.

If the desired print pattern resolution is <NUM> (<NUM>/<NUM> inch)vertical and <NUM> (<NUM>/<NUM> inch) horizontal, one must now consider how to address and actuate thermal actuators as the head moves in the horizontal direction.

<FIG> shows a <NUM> by <NUM> (<NUM>/<NUM> by <NUM>/<NUM> inch) grid with one example of an acceptable prior-art drop placement pattern. If one considers HTR1 in this example one can see that it is actuated after every <NUM> (<NUM>/<NUM> inch) of printhead movement. To optimize print speed, it is desired to actuate the thermal actuator at the highest frequency allowed by fluidic cartridge characteristics. For this example, we will assume an <NUM> thermal actuator. Considering the relationship of:<MAT> the calculated printhead speed is determined to be <NUM>/second (<NUM> inches/second).

With these parameters defined, for a printhead moving at <NUM>/second (<NUM> inches/second), all <NUM> thermal actuators must be addressed and actuated in <NUM> (<NUM>/<NUM> inch) of travel. In this example, the time to address all actuators would be <NUM>. If each thermal actuator was addressed individually the time slice for each actuator would be <NUM> / <NUM> = <NUM>. For thermal microfluidic ejection elements, this time is inadequate to eject the droplet, as the time required to nucleate a fluid is typically greater than 400ns.

For this reason, and in order to reduce the data rate required, an address matrix is defined which allows for multiple thermal actuators to be actuated in the same time slice. The address matrix is typically defined as groups of thermal actuators referred to as Primitives (P) and Addresses (A).

For the <NUM>-thermal actuator example an acceptable address matrix may be 20P x 40A = <NUM>. This would now define the time slice as <NUM> / <NUM> = <NUM>.

For many applications this is an acceptable nucleation time. However, for some thermal print systems it is desirable to provide the ejection energy in two separate pulses to improve the velocity of the ejected drop. In this case, the time slice would need to be further increased. This can be done by changing the ratio of the P × A address matrix. One aspect to consider if the number of Primitives P groups is increased is that this also increases the amount of simultaneous current required for the thermal thermal actuators. For this example, the number of simultaneous fires at <NUM> is fixed so the address matrix will be changed by decreasing Addresses A to <NUM>.

To allow more flexibility in how the energy is applied to the actuators, (overlapped, interlaced etc.) a third variable is added to the address matrix, Fire (F). In this example the address matrix is now defined as 20P x 20A x 2F = <NUM>.

<FIG> shows a timing diagram for a final prior-art address A matrix. As shown, the number of addresses A has been further decreased by the introduction of a fourth variable Extended Address (EA). In this case, it is not done to increase the duration of the time slice but to reduce the width of the address bus required on the silicon chip. Thus, the final address matrix is: <MAT>.

Also shown in <FIG>, there is the addition of two cycles, D1 and D2, where no thermal actuators are actuated. This is a typical practice when using a moving printhead. In the case that feedback from the printer indicates that the printhead is moving too fast or too slow these time periods, dead cycles are inserted to allow for printhead location correction and timing synchronization.

<FIG> represents one possible prior art grouping of primitives P along the thermal actuator array. Each primitive P represents <NUM> thermal actuators. In each of the <NUM> time slices, the number of thermal actuators actuated is determined by the number of Primitives P selected. This can be <NUM> to <NUM>.

The example embodiment shown in <FIG> demonstrates the design constraints when considering a traditional prior-art print head system. In the printing application, the address matrix is defined by the spatial pattern of the thermal actuators, desired print resolution, print speed and the fluidic response of the thermal actuators. In a printing application the primitive P and address A data is often shifted into the printhead using two or more serial data inputs.

<FIG> illustrates a prior art timing diagram for serially loading print data into the printhead. This configuration requires clock (CLK), data (ADATA/PDATA), load (LOAD) and fire (FIRE1, FIRE2). Not shown is a reset (RST) signal used to clear the chip registers. In this configuration the chip requires a total of <NUM> digital inputs.

During each time slice the printer will send a new ADATA and PDATA input stream. To shift the data into the chip one clock edge is required for each bit of data. The LOAD signal is used to latch data into internal registers after the data stream is complete. Once the ADATA and PDATA for the current time slice is latched, the FIRE1 and FIRE2 signals are used to activate the thermal actuators.

As shown in the timing diagram, the data for the next time slice is being clocked into the chip while the thermal actuators for the previous time slice are activated.

A single ADATA or PDATA register may be <NUM> bits or longer. To achieve reasonable print speeds the CLK rate is typically <NUM> to <NUM>.

As shown in this example, a microfluidic ejection element having the capability to print an image may have considerable complexity and require significant computing and input/output speeds.

Another dispensing application, apart from printing ink on media as described above, is one where fluid is dispersed into the environment, such as dispersing a liquid composition into the air. For such an application, it is not necessary to form an image, nor is it required to address particular nozzles at precise times and locations.

In such a dispensing application, the critical performance parameter is the mass dispense rate. This is determined by the number of nozzles and the frequency at which they can be fired. Since it is not necessary to form an image as in a printing application, the computing requirements for the controlling device are much less demanding. In fact, when dispensing into the environment, it is desirable to have a very simple controlling device, which may comprise, for example, a low cost <NUM>-bit microcontroller. For this configuration, a simple interface to the ejection chip is desirable for cost and complexity reasons.

<CIT> discloses a driving circuit for an inkjet printer.

The invention is directed to a method of delivering a fluid composition from a thermally-activated microfluidic ejection element according to claim <NUM>, and a thermally-activated microfluidic ejection element according to claim <NUM>.

The invention described here comprises a microfluidic ejection element and its method of use which implement a simplified interface optimized for dispensing a fluid composition into the environment, such as the air. For dispensing a fluid composition into the air, it is not necessary to individually select and fire nozzles from distinct positions within the nozzle array. Therefore, the microfluidic ejection element of the present disclosure does not provide a means to address a particular nozzle or nozzles in a single time cycle.

The fluid composition may, for example, include inks, dyes, pigments, adhesives, curable compositions, optically activated compounds, metal oxides, bleaching agents, texture reducing polymers, silicones, stains, paints, surfactants, cleaners, malodor reducing agents, lubricants, fillers, perfumes, scents, polymers, polymeric additives, particles, optical modifiers, optical matchers, and other actives such as antibacterial and antimicrobials, and combinations of these or other materials, some of which are further described herein.

With reference to <FIG>, a microfluidic ejection element <NUM> may be a part of a cartridge <NUM>. The cartridge <NUM> may be configured to be releasably connectable with a microfluidic delivery device <NUM>. The microfluidic delivery device <NUM> may comprise a housing <NUM> and a power source <NUM>. The housing <NUM> may receive all or a portion of the cartridge <NUM>. The receptacle may receive a portion of the cartridge <NUM> or the cartridge <NUM> may be completely disposed within the receptacle. The receptacle of the housing may include electrical contacts that are configured to electrically connect with the electrical contacts of the cartridge <NUM>.

The cartridge <NUM> may include a reservoir <NUM> for containing a fluid composition <NUM>. The reservoir <NUM> of the cartridge <NUM> may contain from about <NUM> to about <NUM> of fluid composition, alternatively from about <NUM> to about <NUM> of fluid composition, alternatively from about <NUM> to about <NUM> of fluid composition. The reservoir <NUM> can be made of any suitable material for containing a fluid composition. Suitable materials for the containers include, but are not limited to, plastic, metal, ceramic, composite, and the like. A cartridge may be configured to have multiple reservoirs, each containing the same or a different composition. The microfluidic delivery device may utilize one or more cartridges, each containing a separate reservoir.

The reservoir <NUM> may also contain a porous material <NUM> such as a sponge that creates a back pressure to prevent the fluid composition from leaking from the microfluidic ejection element when the microfluidic ejection element is not in operation. The fluid composition may travel through the porous material and to the microfluidic ejection element through gravity force and/or capillary force acting on the fluid composition. The porous material may comprise a metal or fabric mesh, open-cell polymer foam, or fibrous polyethylene terephthalate, polypropylene, or bi-components of fibers or porous wick, that contain multiple interconnected open cells that form fluid passages. The sponge may be free of a polyurethane foam.

With reference to <FIG>, the cartridge <NUM> may include a microfluidic ejection element <NUM>. The microfluidic ejection element <NUM> may be in fluid communication with the fluid composition disposed in the reservoir.

The primary components of a microfluidic ejection element are a semiconductor substrate, a flow feature layer, and a nozzle plate layer. The flow feature layer and the nozzle plate layer may be formed from two separate layers or one continuous layer. The semiconductor substrate is preferably made of silicon and contains various passivation layers, conductive metal layers, resistive layers, insulative layers and protective layers deposited on a device surface thereof. Fluid ejection actuators in the semiconductor substrate generate rapid pressure impulses to eject the fluid composition from the nozzles. The fluid ejection actuators may be piezoelectric actuators or thermal actuators. Rapid pressure pulses may be generated by piezoelectric device that vibrates at a high frequency (e.g., micro mechanical actuation) or by a thermal actuator resistor (i.e., heater) that cause volatilization of a portion of a fluid composition within the fluid composition through rapid heating cycles (e.g., micro thermal nucleation). For thermal actuators, individual thermal actuator resistors are defined in the resistive layers and each thermal actuator resistor corresponds to a nozzle in the nozzle plate for heating and ejecting the fluid composition from the nozzle.

With reference to <FIG>, there is shown a simplified representation of a portion of a microfluidic ejection element <NUM>. The microfluidic ejection element includes a semiconductor substrate <NUM> that may be a silicon semiconductor substrate <NUM> containing a plurality of fluid ejection actuators <NUM> such as piezoelectric devices or thermal actuator resistors formed on a device side <NUM> of the substrate <NUM> as shown in the simplified illustration of <FIG>. In a microfluidic ejection element having piezo actuators as the fluid ejection actuators <NUM>, the piezo actuator may be disposed adjacent the nozzle such as shown in <FIG> or may be disposed away from the nozzles and still transmit the pressure pulse to the fluid composition to be ejected from the nozzles. Upon activation of fluid ejection actuators <NUM>, fluid supplied through one or more fluid supply vias <NUM> in the semiconductor substrate <NUM> flows through a fluid supply channel <NUM> to a fluid chamber <NUM> in a thick film layer <NUM> where the fluid is caused to be ejected through nozzles <NUM> in a nozzle plate <NUM>. Fluid ejection actuators are formed on the device side <NUM> of the semiconductor substrate <NUM> by well-known semiconductor manufacturing techniques. Thick film layer <NUM> and nozzle plate <NUM> may be separate layers or may be one continuous layer.

The nozzle plate <NUM> may include about <NUM>-<NUM> nozzles <NUM>, or about <NUM> - <NUM> nozzles, or about <NUM>-<NUM> nozzles. Each nozzle <NUM> may deliver about <NUM> to about <NUM> picoliters, or about <NUM> to about <NUM> picoliters, or about <NUM> to about <NUM> picoliters of a fluid composition per electrical firing pulse. Individual nozzles <NUM> may have of a diameter typically about <NUM> microns (<NUM>-<NUM> microns). The flow rate of fluid composition released from the microfluidic ejection element <NUM> could be in the range of about <NUM> to about <NUM>/hour or any other suitable rate or range.

With reference to <FIG>, there is shown the logical interface to the microfluidic ejection element supporting its method of use which implements a simplified interface optimized for dispensing applications. Additional interface elements needed to complete the physical interface (for example, power and/or analog signal connections) are omitted for clarity purposes only. For dispensing a fluid composition into the air, it is not necessary to individually select and fire nozzles from distinct positions within the nozzle array. Therefore, the microfluidic ejection element of the present disclosure does not provide a means to address a particular nozzle or nozzles in a single time cycle. Instead, a predetermined firing sequence is provided, which is determined at design time. Hereinafter, the collection of logical inputs/outputs and other connections (power and analog) will be referred to as an interface.

An exemplary embodiment of the invention is described. A microfluidic delivery element may comprise a semiconductor chip having a control circuit with an interface. The interface comprises a signal (NRST) that, when asserted, resets the logic of the chip to a known starting condition. The interface further comprises a signal (INCR) which causes the logic circuit within the microfluidic ejection element to select the next nozzle from a predetermined sequence. The pre-determined sequence is encoded in the chip at design time. The interface also comprises a signal (FIRE) which actuates the thermal actuator associated with the selected nozzle.

The pre-determined firing sequence of nozzles may be selected to, for example, avoid having adjacent nozzles firing sequentially. In this way, interference (sometimes referred to as fluidic crosstalk) from one nozzle to an adjacent nozzle may be avoided. An example of such an arrangement is shown in <FIG>. As an illustrative example only, <FIG> illustrates nozzles fired in sequence that have six unfired nozzles physically interposed between them.

The microfluidic ejection element comprises a control circuit further comprising a logic circuit for selecting nozzles from a sequence, and additional analog circuitry. An exemplary logic circuit is illustrated in <FIG>. The external INCR signal drives a <NUM>-bit ripple counter. The ripple counter is configured to reset to a count of one (<NUM>) when reaching its terminal count, where the terminal count may be less than <NUM><NUM>-<NUM>, for example. The terminal count may be selected to be equal to the number of nozzles physically present on the chip. The ripple counter is coupled to an address decoder, which may output a set of address lines (Ax) and extended address lines (EAx). The decoded addresses and extended addresses may be configured to select a particular heater. <FIG> illustrates an exemplary microfluidic ejection element having thirty-two thermal actuators <NUM> that that may be physically addressed, and the additional addresses are unused.

With reference to <FIG>, in a normal operation of the microfluidic ejection element, only two signals are used to perform the dispensing of fluid, INCR and FIRE. The INCR and FIRE signals are used in an alternating sequence to advance to the next nozzle in the pre-determined sequence, and to activate the thermal actuator. This allows the use of a small and unsophisticated controller, or to reduce the computational workload on the controller.

The address decoder may be configured to actuate only one nozzle at a time. Or, the address decoder may actuate many nozzles simultaneously, allowing a higher dispensing rate.

The described interface is not dependent on the number of nozzles. While having knowledge of the number of nozzles present is useful to provide a sufficient time for refill of the fluid chambers <NUM>, the interface need not change when the cartridge is reconfigured with a different number of nozzles. Indeed, if the number of nozzles is supplied to the controller at the time of cartridge insertion, the controller may be compatible with future cartridges having different numbers of nozzles without requiring any upgrade.

The energy dissipated by the thermal actuator may be determined by the duration of the pulse applied to the FIRE signal. In this case, the driving source of the FIRE signal must have precise timing. Alternatively, the timing of the pulse applied to the thermal actuator may be determined by the configuration of the chip, and so the timing of the driving source of the FIRE signal is noncritical.

The microfluidic ejection element may additionally comprise embedded memory cells, such that information may be stored during manufacture or during end use. For example, a logic circuit such as shown in <FIG> and <FIG> could be used to access individual memory bits from a sequence of memory bits as well as thermal actuators. In this example, the decoded addresses are sufficient to address all <NUM> bits of memory. In this example, the entire contents of the memory embedded in the ejection chip could be read out by repeatedly toggling the INCR signal, while monitoring the MEMR signal of <FIG>. As individual memory cells are sequentially addressed by the internal logic, the corresponding bit of data is presented on MEMR. The value of the memory bit of data is presented on an output pin corresponding to signal MEMR. The memory cell may be a one-time programmable memory bit, such as a fusible metal alloy. An electrical interface may be provided which translates the state of conduction of the fuse into an open drain electrical output. An example waveform which represents reading data from the interface is shown in <FIG>.

Similarly, a particular bit of memory could be written by toggling the INCR signal until the desired memory bit is selected, and then asserting the MEMW signal. The value to be written to a memory bit is applied to an input pin corresponding to the MEMW signal.

Examples of data stored on the chip may include the identity of the fluid composition disposed in the cartridge, the firing parameters needed by the control logic to properly operate the microfluidic ejection element, or the estimated amount of fluid composition remaining in the cartridge during usage. If the number of nozzles present on the chip is recorded in the memory, the controller element would not have to embed further details about the construction of the microfluidic ejection element, allowing for future version that have more or fewer nozzles.

With reference to <FIG>, <FIG>, and <FIG>, in applications where it is desirable to control the temperature of the ejection chip, a substrate heater(s) <NUM> may be built into the microfluidic ejection element which is distinct from the thermal actuators <NUM> used for heating of the fluid composition. The substrate heater(s) <NUM> are designed to raise the temperature of the entire microfluidic ejection element within a prescribed time. The substrate heater(s) may be controlled by a digital signal, which is labeled SUBH in <FIG> and <FIG>.

For accurate temperature control, it may be desirable to include a temperature sensing element on the microfluidic ejection element. The temperature sensing element could be, for example, a metal alloy resistive strip, where the temperature coefficient of resistivity is well characterized. Measurement of the temperature via the sensing element could be done via the analog signal available on the TSR signal of <FIG>. Continuing the example of the metal alloy resistive strip as the temperature sensor, external circuitry such as a Wheatstone bridge could be provided to translate the temperature dependence of resistance to an analog voltage.

<FIG> also shows additional connections that may be used to complete the physical interface to the microfluidic dispensing element. In <FIG>, HPWR is the power input for actuating the thermal actuators and opening the memory fuses. Depending on the construction of the element, HPWR may be in the range 6V to 18V. LPWR is the power input for the counting and decoding circuitry, and may be in the range <NUM>. GND is the common current return path for the power supplies.

It may be desirable to construct a microfluidic dispensing cartridge having two fluid composition reservoirs. This allows delivery of two fluid compositions either simultaneously or at different times. The simplified interface described here could be easily adapted to this configuration. <FIG> shows how arrays of nozzles may be grouped around multiple fluid paths in a two-channel ejection chip. In this example, a first fluid may be dispensed by firing only the first <NUM> nozzles in sequence. Following this, a second fluid may be dispensed by firing the subsequent <NUM> nozzles, which are arrayed around the second fluid path. Alternatively, following dispensing of the first fluid, the chip could be reset via the NRST signal, so in subsequent firings the first fluid is dispensed again. If the only second fluid is to be dispensed, the controller would toggle the INCR signal <NUM> times (without activating the FIRE signal) to advance to the second group of nozzles. Thereafter, the INCR and FIRE signals would be used alternately to increment and fire nozzles containing the second fluid.

It should be understood that every maximum numerical limitation given throughout this specification will include every lower numerical limitation, as if such lower numerical limitations were expressly written herein.

Every document cited herein, including any cross referenced or related patent or application and any patent application or patent to which this application claims priority or benefit thereof, is hereby incorporated herein by reference in its entirety unless expressly excluded or otherwise limited. The citation of any document is not an admission that it is prior art with respect to any invention disclosed or claimed herein or that it alone, or in any combination with any other reference or references, teaches, suggests or discloses any such invention. Further, to the extent that any meaning or definition of a term in this document conflicts with any meaning or definition of the same term in a document incorporated by reference, the meaning or definition assigned to that term in this document shall govern.

Claim 1:
A method of delivering a fluid composition from a thermally-activated microfluidic ejection element, the thermally-activated microfluidic ejection element comprising a plurality of nozzles (<NUM>), a thermal actuator (<NUM>) associated with each nozzle and a plurality of memory cells, the method comprising:
connecting the thermally-activated microfluidic element to a power source; delivering a first electrical pulse to a first input that selects a thermal actuator from a pre-determined sequence, wherein the first input is in electrical communication with a ripple counter and an address decoder, and wherein the pre-determined sequence is defined by the physical layout of the thermally-activated microfluidic element;
supplying a second electrical pulse of a well-defined width to a second input to activate the selected thermal actuator; and
ejecting a fluid composition from the nozzle associated with the selected thermal actuator; and
reading a memory bit from a sequence of memory bits, wherein the value of the memory bit is presented on an output pin; and
writing a memory bit currently selected from a sequence of memory bits, and wherein only two types of signals in an alternating sequence are used and wherein the first electrical pulse is applied to a first signal and the second electrical pulse is applied to a second signal and wherein said first and second signal are used in an alternating sequence.