An insulin pen -- the size of a marker pen -- manufactured entirely from plastic, wherein a number of the key components required for the accurate dose setting and delivery of the insulin, are moulded from engineering thermoplastics from DuPont. The resulting products are expected to dramatically advance diabetes treatment in India, by offering a portable, discreet, quick and easy insulin dosage system for users on the move.
New disposable and reusable insulin pens, designed by Industrial Design Consultancy Ltd (IDC) in the UK, contain a number of components moulded from DuPont engineering thermoplastics, selected for their quality and performance, and involved the cooperation of DuPont in both Europe and Asia during their production.
DuPont� Delrin� acetal homopolymer resin, a common choice for safety components to obtain highest device reliability, is used for the clutch tube and locking sleeve. DuPont� Zytel� nylon resin has been selected for the drive shaft, inner housing, thumb pad and piston rod cap. Delrin� could deliver excellent dimensional stability in combination with resistance to creep and a certain level of natural lubricity. Where many mechanical movements must occur in an exact sequence, there are components that need the combination of very high impact strength, elastic modulus and tensile strength. For these we chose Zytel�. Crastin� PBT polyester resin, is used for the pen�s dose dial and clip. These parts had initially been specified in Zytel�, however testing revealed that the nylon would absorb moisture in the extremely humid conditions prevalent in India, which in turn would have a detrimental effect on dose accuracy. Its visual appeal and suitability for printing were further benefits to be gained from the change of material.
The overall project was coordinated across Europe and Asia by IDC: the production of high-precision tooling was carried out in Taiwan, testing to ISO standards was conducted in Holland, while the Indian moulder, Shaily Engineering Plastics Limited was responsible for production manufacturing. The spectrum of material offering from a single source along with readily available, local technical support were the greatest benefits of working with DuPont.
The fact that the pen is made completely from plastics meant that moulding the various components, including the dosing and delivery mechanisms, was critical to its success. IDC also managed the design and delivery of tools from Taiwan. Another cost saver was to make the designs of disposable and re-usable versions as similar as possible by ensuring some common components across the two products. Plastics used in the various ratchets, gears and other mechanisms of the pens included acetal, nylon and PBT. One key factor, which helped to differentiate it from similar products, was the method of assembly: by hand. All competitor pens are assembled using at least partial automation. In India, it is more cost-effective to use manual labour. The whole design time of around 22 months, from conception to final product, including the management of complex moulding projects, was fast for such a product, especially as IDC had never before designed an insulin pen. The final product is compact and discreet, around the size of a marker pen, and has an easy dosing facility for people with vision or dexterity problems. The internal mechanisms give an audible and tactile 'click' when setting and delivering a dose. The re-usable version also has a magnifying dose window.