Fig 1.
A visual guide to the open-source autoinjector’s digitally manufactured (parts A-G) and purchased components (parts H, I, and J). (A) Grey coloured injector cover is the first part placed in the back from left to right. (B) Black coloured two-spring-hold at the second position of the back row. (C) Yellow coloured plunger shown as the third part. (D) Red coloured connector in the centre of the back row. (E) Blue coloured spring-cone-retainer at the fifth position in the back row. (F) Purple coloured spring-retainer in the sixth position. (G) White coloured syringe-cover in the seventh position of the back row. (H) 35 mm compression spring in the front left corner of image. (I) 61.5 mm fraction of the 81.5 mm compression spring in the front centre. (J) 20 mm fraction of the 81.5 mm compression spring in the front right corner of image.
Table 1.
Bill of materials for the device’s 3-D printed components and springs.
Table 2.
Print settings for 3-D printed components of autoinjector.
Fig 2.
Remove built-in support on injector cover (A) and establish two springs (I and J).
Fig 3.
Internal view of the injector cover (A) assembly with parts H, B, I, and C.
Fig 4.
Blue (E) and purple (F) spring retainers fitted around the 20 mm compression spring (J).
Fig 5.
Syringe cover (G) prepared with parts E, F, and J to dampen the spring force.
Fig 6.
BD Insulin syringe (K3) loaded with 1.0 mL of ethyl alcohol and green food coloring.
Table 3.
Tested Becton Dickinson (BD) insulin syringes with varying capacity, needle length, and gauge [45].
Fig 7.
Align prefilled syringe (K3) with syringe cover (G), retainers (E and F), and small spring (J).
Fig 8.
Pushing the plunger (C) inside the injector cover (A) to prepare the spring force.
Fig 9.
Distance that plunger (C) must be displaced to make contact and lock onto the button.
Fig 10.
Loaded autoinjector (A, H, B, I, C, and D), ready for assembly with syringe component.
Fig 11.
Fully assembled spring-driven autoinjector with a prefilled syringe, which is ready to be administered.
Table 4.
Outcomes of free-fall testing for one autoinjector that was dropped seven times in three orientations.
Table 5.
Dose-delivery efficiency for Vset1.
Table 6.
Dose-delivery efficiency for Vset2.
Table 7.
Dose-delivery efficiency for Vset3.
Fig 12.
Gaussian distribution of the dose efficiency for the 1 mL BD Insulin syringes (Vset1).
Fig 13.
Gaussian distribution of the dose efficiency for the 0.5 mL BD Insulin syringes (Vset2).
Fig 14.
Broken connector (D) after dropping.
Fig 15.
Open-source syringe pump assembled and able to function without connector (D).