The materials for contact lenses are hydrogels or silicone hydrogels. In consideration of production capacity and yield rate, most manufacturers adopt the injection molding method, which involves injecting a small amount of hydrogel or silicone hydrogel into the upper and lower plastic mold model that has been computer-calculated for prescription. Hydrogels and silicone hydrogels contain initiators, which need to be cured by UV irradiation. Once cured, they are called dry films. After the hydration process, they become the commonly used soft contact lenses.
Recently, there has been a growing demand for pupil enlargement lenses and colored contact lenses, which require two injection processes. The printed surface is sandwiched between two layers of lenses, so the colorant does not directly contact the eyes, making the lenses more comfortable and safe to wear.
Contact lenses are thin and lightweight, and the amount of injected material is very small (less than 0.1 ml). Especially for special lenses such as pupil enlargement lenses that require two injection processes and need to consider comfort, the amount of injected material is very small and requires extremely high precision. In addition, the raw material cost is high (especially for silicone hydrogels) and the quality requirements are high, so it is necessary to accurately and stably inject the required amount of adhesive to improve yield rate and reduce costs. Therefore, the selection of the injection pump is crucial.
Common Injection Methods for Contact Lenses
The common equipment used for injection of contact lenses includes peristaltic pumps, piston pumps, and pneumatic dispensing valves. Peristaltic pumps are commonly used in medical fluid delivery systems, where the fluid only contacts the pump tubing and not the pump body. However, the disadvantage is the low precision, with a repeat precision of around 10% under the condition of micro-injection of contact lens materials. Pneumatic dispensing valves are subject to the instability of the pressure cylinder or air pressure of the stored fluid, resulting in inconsistent dispensing amounts. Under the requirements of micro-injection of contact lens materials and the condition that the material is prone to solidify, the repeat precision is around 15-20%. Neither of the above injection methods can meet the requirements for precise injection of contact lenses.
Piston pumps are volumetric pumps that rely on the reciprocating motion of the piston in the cylinder to create a pressure difference that generates flow. By changing the stroke of the piston, the flow rate can be controlled with high precision. UBA's piston pump has extremely high measurement accuracy and repeatability, maintaining a repeat precision of ±1% or less under micro-injection of contact lens materials (below 0.1ml). It is not affected by the solidification of the material during operation and still maintains the set output. UBA's micro-piston pump adopts a diaphragm valve design, and can be equipped with a membrane that complies with medical standards as a columnar pump for contact lenses.
UBA Precision Metering Pump
The UBA Precision Metering Pump has extremely high metering accuracy and repeatability, with accuracy better than plus or minus one percent.
The E-D series top-mounted micro-control valve design facilitates the rapid removal of bubbles and ensures more stable liquid injection.
The E-D series uses a stepper motor to drive a precision lead screw system, and all injection parameters can be set through a color touch screen, achieving digital injection adjustment. There is no need for any mechanical adjustment of the pump, and the injection volume can be accurately controlled. The standard pump model has a full 316 stainless steel structure and can be optionally equipped with a smoothness of RA value 0.2 standard pump body.
The E-D series adopts a diaphragm valve design, which does not trap the pump and has a long service life of up to 10 million cycles. The diaphragm material can be selected from EPDM, FKM, or Kalrez® perfluoroelastomer, which meets the requirements of medical device manufacturing. It is suitable for the quantitative injection of low-viscosity liquids in contact lenses water gel or silicone water gel. This series performs best in micro-injection and can complete micro-injections from 0-0.1ml with high repeatability, which improves the yield rate and reduces material waste.