Transcutaneous signal transmission without breaching the skin's natural barrier to infection

Our current neurophysiological experiments in awake behaving monkeys require implantation of electrodes to record electromyogram (EMG) from the arm and hand. Wires from these electrodes are fed sub-cutaneously to a connector on the back. The electrodes yield high quality, trouble free recordings for over one year. However, the permanently open wound around the connector often becomes infected, impairing the welfare of the animal and reducing the quality of data which can be gathered. In this application, we seek to develop a novel implantable electronic device. This will amplify and digitise up to 16 channels of EMG recording (5kHz sampling rate per channel), and transmit the signals through the skin by radio. Power will be supplied by inductive coupling to an implanted coil antenna. The printed circuit board will use a flexible substrate, permitting the circuit to mould to the natural curvature of the animal's back. The implant will be designed such that the skin can be closed over it. This will prevent infections caused by the breach of the skin's natural barrier to infection. After bench testing, a prototype will be tested in a rabbit model, followed by long-term testing in macaque monkeys. All animal testing will be performed as part of our ongoing research programme; no animals will be used solely to test the system to be developed here. We consider that repeated infections associated with the back connector currently represent the major welfare cost to our monkeys of participating in experiments. Eliminating these infections would be a considerable refinement of technique. In addition, such infections can reduce the quality of behavioural data which is obtained, due to the clinical malaise suffered by the animal. This limits the science which can be achieved (i.e. new knowledge discovered) per animal used. Finally, severe infections may cause an experiment to be terminated prematurely, before sufficient data has been gathered. This would require the use of a further animal to complete the project. The proposed solution can therefore also achieve a reduction in animal numbers. Although this proposal is targeted at a particular need, arising from our work in monkey motor system, the issue it addresses is fundamental and of widespread importance. Many experiments require signals to be transmitted transcutaneously, and suffer from the same problems with infection caused by wired interconnects. We plan to develop and commercialise any system which we develop to make it widely available to other laboratories.

• Research Review 2013: Reducing infection risk in monkeys used to study the control of movement
• Further funding: NC3Rs Project Grant: Wireless high-bandwidth trans-cutaneous signal transmission, April 2012, £71,982