A novel pressure-sensitive sensor for applications in patient's monitoring

Scoliosis is a medical condition in which a person's spine has a sideways curve. The curve is usually "S"- or "C"-shaped over three dimensions. Adolescent Idiopathic Scoliosis is by far the most common type of scoliosis (70-80 %), affecting children between ages 10 to 18; it’s found in as many as 4 in 100 adolescents. In general, AIS curves progress during the rapid growth period of the patient. Idiopathic means that the condition has no identifiable causes although significant research is ongoing, including the genetic basis for AIS. Approximately 30% of AIS patients have some family history of scoliosis, which would indicate a genetic connection. Bracing is a treatment for idiopathic scoliosis, is normally done when the person has bone growth remaining and is, in general, implemented to hold the curve and prevent it from progressing to the point where surgery is recommended. Therefore, Braces serve to maintain, and, in some cases, reduce the spinal curve to prevent progression of the deformity by applying corrective forces. Scoliosis braces can be rigid, flexible, or composite and can utilize passive or active corrective mechanisms. Many braces use a three-point pressure principle as the method of correction. The magnitude and direction of corrective forces applied by a brace to the spine remain unknown and are a common concern for clinicians and orthotists who are tasked with making design alterations. For this reason, this study aims to develop a novel, completely hand made wearable sensor that is capable of measuring forces applied by a brace to the spine. The first sensor developed is hand made. Instead, the second is completely built with an embroidery machine. Both of them combine conductive and non-conductive materials to create a resistive sensor. The resistive sensor exploits one conductive layer and works as a strain gauge that changes its resistance when it is squeezed. A total of six different sensor models were tested to evaluate their properties. From this analysis, the best solution in terms of accuracy, low noise and repeatability was one of the embroided ones. The performance of all the sensors was also tested once applied to the brace. The sensors showed promising results distinguishing the different forces applied by the brace. Thanks to the promising results showed by the embroided sensor and its features of thickness (less than 3 mm) and low cost (less than 3$), it can offer a valid alternative to the current methods for measuring forces applied by a brace to the spine. With the possibility to use embroided sensors inside the brace, both physicians, orthotists and patients can obtain continuous feedback, offering the opportunity of brace design alterations.