These tiny injection syringe needles could make blood test and injections pain-free for millions of diabetics.
A tiny needle to use in syringes to make injections pain-free has been developed by researchers from Indian and Japanese universities. The new microneedles, once in the market, could help diabetics to draw blood test samples and inject insulin in a rather painless way. The microneedle is really very small: as small as the size of a mosquito’s proboscis or the part of its mouth which they use to bite us.
The new syringe needle is atleast 15 times smaller than the conventional ones. Its inner diameter is only around 25 microns and the external diameter – 60 microns, compared with an ordinary syringe needle which has an outer diameter of around 900 microns.
The most striking aspect of this microneedle is that it can inject drugs or draw out blood in a painless way. The new microneedle won’t snap easily either. The robust injection device is made of stronger titanium and related alloys, in contrast to previous silicon dioxide microneedles.
The microneedle can be used in blood testing sensors for diabetics. These needles can penetrate as far as 3 millimetres into skin and reach capillary blood vessels. The researchers have calculated that this tiny syringe needle can extract 5 microlitres of blood per second. This volume of blood is sufficient for measuring blood-sugar levels in diabetics using a glucose sensor.
The new microneedle’s relatively smaller size compared to earlier models also means that surface tension effects are exploited further for its design. Micro injection needles work by suction or capillary process – the same flow that draws water up into trees. The microneedle design uses a shape-memory alloy to drive the needle into skin and a micro-pump for delivering drugs. The latter could be used to inject drugs into the patient with minimum pain, when required.
“The working principle of this device follows on from our discovery that in a well-designed microneedle, surface tension forces may overcome resistance from friction and draw up blood with unprecedented efficiency,” said Suman Chakraborty from the Indian Institute of Technology Kharagpur, India who developed the needle along with his Japanese counterpart Kazuyoshi Tsuchiya of Tokai University.
How the microneedle works
Explaining the working principle of microneedles, Chakraborty said the microneedle rests underneath the center of a blood-sampling tank. A heated shape-memory alloy spring causes the needle to move a few millimeters to generate the skin penetration load, after which a bimorph lead zirconate titanate (PZT) piezoelectric microactuator olds the needle steady for a few seconds. The negative pressure in the blood-extraction tank generated by the deflection of the microactuator results in blood extraction.
At the same time, blood is pumped and extracted using an applied ac voltage. The electric current is then shut off, and the bias spring returns both the microneedle and the pumping system to their initial positions. A biosensor embedded in the pumping unit’s lower tank senses the presence of the extracted blood.
Blood extraction requires overcoming friction, emphasizes Chakraborty. “When the blood enters the needle, it slows down due to frictional resistance. The driving surface-tension force that favors needles with microscale dimensions, however, tends to get dynamically augmented through an alteration of the effective contact angle at the capillary meniscus as the blood sample tends to slow down in the needle. This dynamic evolution of the surface-tension force helps the blood to overcome frictional resistance to a great extent.”
Chakraborty and Tsuchiya are now planning to commercialize their new injection microneedle. However, like any other new invention, they too are facing some challenges to overcome, including cost, scaling up the fabrication method, and making it more user-friendly. “This new blood extraction is interesting, but I question its ability to be fabricated and initialised en masse,” said Geoffrey Thomas of the University of Calgary, Canada, who is working on a similar blood glucose sampling and analysis project.
Orignal source:Thanks to www.dancewithshadows.com
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