Microneedle allows injection with significantly reduced pain by inserting it into the shallow skin layer. It has great potential to improve medical treatment in the future such as vaccine administration and diabetes care. We will take advantage of the features of microneedle to create various medical applications and new medical treatment opportunities.
Fig. 1 Advantages of Microneedle
Fig. 2 Application deployment
Features of ASTI-Microneedle
Our microneedle (prototype) has been realized by our mass-producible plastic injection molding, making full use of accumulated micro molding technology, assembly technology, material technology, etc. and has the following features.
（1） Fine needle shape and sharp needle tip of 10µm or less
（2） Fine hollow flow path realized by stacking procedure (flow path of 80 µm)
（3） Highly flexibility in shape of needle
・ Transverse or downward flow path opening (hardly to clog)
・ Double-ended needle (allows easy drug drawing)
・ Reverse shape and arrowhead shape (high tip strength)
（4） High hardness biodegradable resin (PGA) * Polyglycolic Acid
・ High ability of puncture
・ Safely handled and easily disposable
（5） By making the basic unit (microneedle unit) a row of several needles (current 6), arrangement according to applications is flexible.
・Lure taper connection
・Medicinal needle connection (double ended)
・Stacking is unnecessary for chemical-coated microneedle and piercing applications (sole use of main needle is possible).
＊ Double ended type microneedle
＊ Making the hollow by precisely stacking the main needle having the open flow path and the flow path cover.
Type of microneedle
Our microneedle is flexible to customize according to the application and usage form. A variation includes double-ended needle (for prefilled syringes), connector of lure taper (for general syringes), needle array etc.
It consists of a needle on both sides. One side of the needle group is for insertion into skin (microneedle), and the other needle group is for puncturing the rubber plug of prefilled syringes and for drawing medicine into the microneedle side (supply needle).
Fig.5 Diagram of double headed microneedle
Fig.6 Diagram of microneedle connected with prefilled syringe. (under development)
（2）Microneedle with lure connector
It is a combination of a connector (lure taper connector) suitable for the tip of a general injection syringe and a microneedle unit (one row microneedle), which can be easily attached to various kinds of commercially available syringes.
Multiple microneedle units are arranged side by side. Various array pattern will be possible by arranging the units to enable to apply perpendicularly or obliquely. It enables to deliver profuse medication to a wider area.
Evaluation of strength and ease of insertion is critical for microneedles. Liquid feed property, or liquid feed resistance is also an important subject for hollow needles because of narrowness of the lumen. We are proceeding with these evaluations through industry-academia collaborative research toward practical clinical application of microneedles.
Puncture resistance measurement
We are trying to optimize the needle shape looking at evaluation of the displacement amount and the puncture resistance. Estimation of insertion depth is also one of the factors of such evaluation since changes in needle shape reflect puncture resistance data. We also perform experiment on dummy skin (silicone rubber etc.) and laboratory animals.
Fig. 11 Puncture resistance measurement
Fig. 12 Puncture resistance and displacement amount
We have constructed our own fluorescence solution delivery measuring equipment to measure liquid deliverability, such as flow resistance etc., for optimization of the flow channel shape. We advance intradermal delivery evaluation with fluorescent pigment.