Sara Abdollahi, PhD Candidate, Carnegie Mellon University / Department of Biomedical Engineering
Adam Feinberg PhD, Associate Professor, Carnegie Mellon University
Three dimensionally (3D) printed soft and flexible materials like polydimethylsiloxane (PDMS), can house electronics for wearable sensors and medical devices. However, many silicone pre-polymers are challenging to 3D print because they are liquids prior to curing. To address this, we previously developed a Freeform Reversible Embedding (FRE) technique where liquid silicones are 3D printed (embedded) within a support bath, cured and then removed. Here, we developed an algorithmically guided approach to evaluate print parameters (e.g. print extrusion speed, support bath type) to further improve fidelity and mechanical integrity of the printed part. Through this process we determined that a support bath composed of Carbopol 940 at 0.2% w/v concentration maximized PDMS print fidelity using a cylindrical shell as the target part. We then developed a patient-specific fit 3D toe cuff using the NextEngine 3D scanner to generate a custom 3D model. The PDMS cuff had an elastic modulus of 1.2 ± 0.1 MPa, similar to cast PDMS of comparable dimension. Integration of the PDMS cuff with optoelectronic pulse oximetry components enabled heart rate measurements. This is a step toward a wearable pulse oximeter that continuously monitors blood oxygen in patients with peripheral arterial disease.