A typical lateral flow device includes a test strip and a plastic housing. The housing can consist of more than two pieces such as ports for sample, etc. The focus here is on the development and manufacturing of the test strips which are in most cases composed of the following parts: 1. plastic backing with adhesive and release liner, 2. a nitrocellulose membrane, 3. a conjugate pad, 4. a sample pad and 5. in some cases cover layers are used over the composite device. The various materials can be supplied in roll, sheet or strip formats. The membrane is already in a converted mode for lamination onto the plastic backing. The other materials can be converted to the correct widths for reagent processing and lamination before or after reagent processing.
The typical reagent processing steps include the following:
Dispensing test and control lines onto the membrane. This can be done on membrane before lamination or after. The blocking reagent can be dispensed in parallel with the test and control or afterwards. The dispensing can be done with master strips or in roll formats. The typical method of dispensing onto the membrane is in a strip format using XY tables with bare membrane before lamination or master strips where the membrane has been laminated onto the plastic backing. The strip length is typically 300-500 mm. The blocking reagent can also be dispensed using a third dispense channel in parallel with the test and control lines.
The same dispensing as described above can be done on a reel-to-reel format using a roll format where the membrane is free standing or pre-laminated to the backing material.
Line dispensing can be done with either a contact or non-contact dispensing system. The non-contact is preferred over the contact as contact dispensing leaves a small indentation on the membrane surface which degrades the quality (CVs) of the dispensed line.
Conjugate and Sample Pads
Historically these two pads have been processed using impregnated sheet stock followed by drying and then cutting to width and lamination to a backing card. It is also possible to impregnate web materials using an in-line reel-reel machine. The problem with bulk impregnation is that the basic material stock is not very uniform and therefore the concentration of impregnated material is not uniform along the length of the final part for lamination to the backing. This results in degraded CVs for the finished product. The CV problem has been greatly improved by using quantitative dispensing with either the reel-reel or XYZ dispensing platforms where the reagent is very accurately dispensed along the lamination direction so that each cut lateral flow strip will have the same volume of dried reagent.
Dispensing and Impregnation Products
BioDot provides a number of dispensing and impregnation options for processing lateral flow test strips formats as denoted below which can be integrated into different platforms (described below.)
The FrontLine HR™ dispenser format consists of dragging dispense tips where each tip is connected to a syringe pump that feeds reagent from a reservoir though the tip onto the membrane which is moved on the surface of the membrane to create a line of dispensed reagent using an X only motion. Multiple tips can be mounted on the motion head with adjustable spacing to position the tips relative to each other and a membrane fiducial. There are two FrontLine tip configurations which can produce line concentrations from 0.25 uL/cm up to 4 uL/cm with CVs in the range of +/-3-5%. The FrontLine dispenser does cause a small indentation in the membrane surface which can degrade performance CVs for the lateral flow test.
The BioJet HR™ dispenser format consists a solenoid with a dispense tip connected to the syringe pump which can dispense single drops with CVs in the range of +/-3-5%. Lines can be dispensed by overlapping drops on-the-fly to form a continuous line on the nitrocellulose membrane. The drop range is 2.6 nL up to 2 uL. Line concentration from 0.2 to uL/cm can be dispensed with the BioJets for lateral flow applications with CVs in the range of 3-5%. The BioJet technology does not cause any deformation in the membrane with dispensing.
The BioJet Ultra™ dispenser format consists of a piezoelectric actuator which can dispense drops over a range of 100-1000 pL with viscosities in the range of 1-500 cpi. This dispenser is used for the new Symbolics lateral flow format based on the use of reagent pixels to create Alfa numeric symbols and array formats on the lateral flow platform (see Symbolics.) This dispenser can be use with XYZ and RR120 platforms.
The AirJet HR™ dispenser format consists of aerosol actuator connected to as a syringe pump and a pressure line which mixes the regent with compressed air to eject an aerosol with a cone shape as it is emitted from the tip of the actuator. The volume deposited on the substrate is determined by the flow programmed into the syringe pump and the speed of the substrate relative to the dispense head. The diameter of the cone hitting the substrate is determined by the distance between the dispenser tip and the substrate as well as the pin position in the aerosol head. This type of dispenser can delivery line volumes on the substrate in the range of 0.5uL/cm up to 34 uL/cm. This dispenser is useful for dispensing conjugates and blocking solutions and can also be used to dispense antibody lines on membranes in the range of 0.5-2 mm wide. One of the important features of the AirJet dispensing is that when used for conjugates the reagent is delivered as a mist which when dries provides for both fast and efficient solubilization in the sample passing through the conjugate pad thus providing improved quantitation of the test.
The PolyDrop™ is a dispenser based on the use of a HR™ or Elite™ syringe pump with needle tip for ejection, near contact or contact dispensing of reagents. For lateral flow the principle application would be for impregnation of various pads such as conjugate pads. In this case the tip is set up for near contact dispensing using either XYZ3200 or RR120 platforms. The pad can be precut to the lamination width or use sheets on XY platforms or webs on the RR. In this case multiple dispenser are used based on the pitch of the cut pad width. Sheets are dried off line in convection ovens and then slit for lamination. Webs are dried on-line on the RR and then transferred to a slitting machine to slit to the web width and then re-rolled for use on an in-line lamination machine. The above operations can be done with the AirJet types of dispensers also.
It is also possible to use bulk impregnation with sheets in baths or on-line with the RR120 which has an impregnation module for dipping web materials followed by drying. Neither of these options are recommended due to the basic non-homogeneous nature of these materials which leads to variations of dried reagent concentrations. This problem is eliminated by the use of quantitative dispensing of reagents as described above.
The tandem pump configuration is used for both FrontLine and BioJet dispensing on different BioDot platforms requirement dispensing without delays for syringe refilling.
BioDot has international patents for the BioJet HR™, BioJet Ultra™, AirJet and the use of solenoid and aerosol dispensed heads combined with the use of syringe pumps to achieve quantitative dispensing. There are additional patents for the use of the Tandem pump configuration which eliminates delays and line distortions due to syringe refilling cycles. There are issued patents in the US, China and Europe.
Dispensing and Impregnation Platforms
BioDot provides a number of reagent dispensing platforms that are designed for a combination of R&D and production activities. In both cases the same dispensing technology is used which allows for R&D validated processes to be efficiently transferred to the manufacturing environment.
The ZX1010 is a flexible motion/dispense system, with a pneumatic Z-axis and a fully programmable X motion and dispense parameters. It has the capability for simultaneous dispensing or individual dispensing of lines and dots (BioJet only). A maximum of 4 AirJet HR, 8 BioJet HR™, 8 FrontLine HR™, or 8 PolyDrop™ dispensers can be configured.
The XYZ3210 is a flexible XYZ motion/dispense system, with a motorized Z-axis and fully programmable X and Y motion and dispense parameters. The dispense area is 46 x 26 cm. This allows for multiple master cards or sheets on the deck. The XYZ3210 also has the capability for simultaneous dispensing or individual dispense of lines and dots. Using the 3060 platform, a maximum of 4 AirJet HR™, 8 BioJet HR, 8 Frontline HR™, or 8 PolyDrop™ dispensers can be configured. The machine is also supplied with up to two 4 port degasses for the BioJet HR dispensers. Typical dispense speeds are up to 50 mm/sec.
The XYZ series systems are powerful production tools for rapid test development and manufacturing. The XYZ3060 is a flexible XYZ motion/dispense system, with a motorized Z-axis and fully programmable X and Y motion and dispense parameters. The dispense area is 50 x 7 cm. This allows for one master card or sheet on the deck. The XYZ3060 also has the capability for simultaneous dispensing or individual dispense of lines and dots. Using the 3060 platform, a maximum of 4 AirJet HR, 8 BioJet HR, 8 FrontLine HR, or 8 PolyDrop dispensers can be configured. The machine is also supplied with up to two 4 port degasses for the BioJet HR™ dispensers. Typical dispense speeds are up to 50 mm/sec.
RR120 and RR120-Ultra
The RR120 is a modular, in-line processing system that includes, web feed, dispensing with web tracking, vision inspection/bad part marking, impregnation, drying and take-up in a controlled humidity environment. The system provides processing of webs from 5-120 mm widths. It can be used for processing materials for lateral flow or dry chemistry applications. It can accommodate all of the BioDot dispensing modules using Tandem pump configurations. Additional modules can be added for lamination, punching, cutting, etc.
The RR120-Ultra is an extension of the RR120 where the module that includes the tandem pump dispensers and vision inspection is replaced with a new BioJet Ultra module which uses arrays of Ultra dispensers for printing alpha numeric and arrays formats on membrane with on-the-fly dispensing. The RR120-Ultra represents the high throughput manufacturing system for Symbolics types of lateral flow formats.
This system is a platform based on the use of piezoelectric dispensing with drops in the 100-1000 nL for generating pixel reagent patterns on nitrocellulose membrane for lateral flow formats based on the Symbolics concept for alpha-numeric and arrays formats. It can also be equipment with a combination of BioJet Elite with the BioJet Ultra to provide for both picoliter and nanoliter dispensing on the same system. The system operates in the AD mode of reagent handling. The system can hold up to three laminate cards up to 200 mm long. The integrated vision system provides fiducial finding for placing the reagent symbols relative to a cutting fiducial for cutting devices into individual test strips. This system also includes a horizontal camera system for measuring drop size in the picoliter range. A vertical camera is provided for fiducial finding and dispense pattern imaging. This system is designed for process and design development for R&D.
This is the same as the AD2030 but with a larger XY deck dimension. See the product sheet for BioJet Ultra.
Vision Inspection for Lateral Flow Dispensing Platforms/Bad Part Marking
BioDot provides a variety of automated camera vision solutions in order to increase reproducibility in manufacturing as well as reliability in part inspection. Automating the inspection process can lead to a higher quality of product and increased yield as well.
XYZ & RR120: For production level systems such as the RR120, camera vision inspection is essential for high volume manufacturing while maintaining 100% inspection. BioDot offers 2 camera types for the RR120 system; a high-speed inspection system and a high-speed/high-resolution version. On membrane-based materials, the standard high-speed camera system is capable of inspecting up to 5 dispense lines simultaneously at rates up to 100mm/s. The standard inspection package includes inspection of line position, line width, deviations in position or width, gaps, bulges, narrow/neck-down, satellites, and concentration. Additional tools may be added based on application specific inspection requirements. For fiber pad inspection of conjugate dispense, a high-resolution camera can be used to inspect line position, width, deviation, concentration, gaps, and spikes. Filters can be added to enhance image quality for different reagents and materials. The same inspection system can be applied to card-based XYZ style systems.
AD Series Systems & Ultra: AD series systems utilize a vertical camera looking directly at the nest. The vertical camera is used for device positioning, calibration, fiducial inspection, and pre/post dispense analysis. Controlled by BioDot’s graphical user interface, the vertical camera allows for the ultimate user-friendly experience with its simple “click to move” features. AD Series Ultra systems consist of 2 cameras; (1) vertical camera looking down at the nest and (1) horizontal camera to capture dispensed drops in flight. The vertical camera has all of the capabilities as other AD series systems. The horizontal camera, unique to the Ultra set-up, allows users to capture individual drops in flight, providing real time analysis of drop size, morphology, and velocity.
Lamination can be performed using a manual batch process or a fully automated in-line system.
The LM5000 Clamshell is designed to assemble a lateral flow assay comprised of multiple materials (typically a nitrocellulose membrane, a sample pad, a conjugate pad, and an absorbent pad) onto an adhesive backing material. It contains top and bottom vacuum nests to hold strip materials in place and is operated manually. Standard or customized nest inserts are available and are easily interchangeable so that multiple assay designs can be laminated.
The LM9000 Continuous Laminating System is a modular design to accommodate various numbers and types of materials. Each material is fed from adjustable spindles through guides and under a pressure capstan roller to assure complete adhesion to the plastic support backing. The system provides the ability to individually remove kiss cut adhesive liners for individual laminate materials. For fragile materials like nitrocellulose, alignment is controlled through automated tracking. After lamination the materials can either be cut and stacked in a collection chute or rewound onto a take-up reel. Other process steps such as dispensing, slitting, punching and inspection can also be integrated into the system.
Slitting, Cutting and Bottling
The SRR5000 is a web fed system where processed web material is slit into a number of thinner webs for subsequent lamination on backing cards for lateral flow, dipstick and other such devices. The machine consists of a feed reel followed by a set of individual rotary blades spaced at the desired cut web width. The individual slit webs are then rewound onto hubs for transfer to a lamination machine. Examples would slitting sample and conjugate pads that have previously impregnated for final assembly.
The CM5000 Guillotine Cutter is a robust, fully automatic workstation that provides high quality precision cuts. Blades are made from hardened steel, and specially coated to improve ejection of cut strips and reduce glue build up. Cut widths and quantities are easily programmed through its handheld terminal. Programs may be stored for system reference in either development or manufacturing environments. Options include: anti-static ionizer, leading edge sensor and target sensor.
Bottling Test Strips
The Bottling System 6000 is designed to take either master cards or reel feed of the final laminate into the cutting of test strips for bottling. The master cards are magazine fed while the reel feed is using a large diameter reel to feed the laminate to a guillotine cutter with leading edge sensor and bad mark sensor. The leading edge sensor insures the width of the cut strips which are dropped to a conveyor which sends the good strips to a bottling station. The final laminate is both inspected at the dispensing station for quality of dispensed lines and at the lamination machine for correct placement of individual layers. The final laminate then portrays a combination of bad part markings which are recognized by the bad mark sensor on the cutter. Bad parts are removed at the cutter station and only passed parts go to the bottling process. The individual bottles are manually placed with and removed with manual placement of the bottle cap.