Making steady hands

That moment that makes you grimace, as the stabbing pains shoot into your arm, intensifying with every little movement. Even worse is when there are several attempts, each as unsuccessful as the last. Whether at school or at the hospital, most of us have been the victim of a painful injection. There can be for a number of reasons for this, but unsteady hands have a lot to answer for, as does slight variation in getting the needle in the right place. Everyone shakes, even the most skilled surgeons have hand tremors that typically range from 50- 100µm, and although this may not seem like a lot, it can be the difference between a moment of displeasure, and minutes of pain followed by a sore arm for hours after. Micro-surgery is even more critical for steady hands. Operating on a nerve fibre, or a retina, requires very precise movements. Even the slightest unintended movement can make surgical tasks impossible to complete, or worse, result in catastrophic injury to the patient. The Challenge The challenge this month is to therefore come up with a less painful method of injecting medicines and vaccines in to the arm. Though Star Trek-style hypo sprays might be ideal, the technology doesn't really exist yet, so a hypodermic needle is still likely to be needed. The key design driver for this challenge is therefore to remove the shake or tremors from a person's hand, no matter how minute, as well as to help nurses and doctors carry out an injection with literally pinpoint accuracy. Although there are robot arms that can be used either to steady a person's hand, or replace it all together, that is not the aim of the game for this challenge, as the device still needs to be easily handled, relatively low cost, and operated by hand in a confined space. The solution is not so much about getting the hand to shake less as it is about sensing these tiny movements and compensating for them in one way or another. The solution to this challenge uses off-the-shelf technology and is about clever integration rather than developing new technology. While the sensing equipment is mainly used to counteract tremors, it should also have the ability to improve the aim of where an injection will be placed on the body. The components and equipment used are well known but have been assembled with not inconsiderable elegance. When you see it you may consider it obvious. In the meantime, see if you can come up with a solution. -Solution- Solution to November 2012 Coffee Time Challenge The solution to the November Coffee Time Challenge of how to make injections less painful comes from research work carried out at Johns Hopkins University which have developed a device called SMART – smart micromanipulation aided robotic-surgical tool). The device combines an optical coherence tomography imaging technique as a distance sensor with computer controlled piezoelectric motors to actively stabilise the tip of the tool. Researchers have been able to integrate a near infrared laser that shines out of the tip of a needle and onto the patient's skin. The laser acts as a distance sensor, measuring the time it take for pulses of light to be received back. By analysing this data via an onboard computer, it can determine when and by how much the tool is wavering in relation to the target tissue. The information is then fed in to the piezoelectric motor attached to the tip of the needle, which can then actually compensate for these movements by performing tiny actuation. The system can make adjustments at a rate of 500 per second which is far quicker than a typical hand tremor which typically shakes at rate of 15 per second. The motor has a resolution of about 1nm and the needle has a travel of about 12mm in diameter. The system uses a single fibre optic cable is so small and flexible, the researchers were able to easily integrate it into the front of a tool used for eye surgery. By continually sending and receiving the near infrared laser beams, the high-speed fibre-optic sensor precisely measures the motion of the probe. This creates a series of 'station keeping' manoeuvres that compensate for the surgeon's hand tremors. During the next few years, the researchers hope to take their instrument from the laboratory to the operating suite, and with additional refinements expand its use to other fine-scale surgeries. www.jhu.edu