Novel 3D printing-based probe for impedance spectroscopic examination of oral mucosa: design and preliminary testing with phantom models

Abstract

The diagnosis of oral potentially malignant disorders currently relies on histopathological examination of surgically removed biopsies causing pain and discomfort for the patient. We hypothesise that non-invasive bioimpedance spectroscopy (BIS) method would overcome these problems and could make possible regular screening of at-risk patients. Previously several handmade probes have been introduced in such BIS studies. However, for the first time, we aimed to design a 3D printed probe and test it with model samples (saline solutions, cucumber and porcine tongue). We found that it is extremely crucial to select proper printable materials and optimise electrode geometries to avoid electrochemical corrosion problems, short-circuiting and other signal instabilities related to miniaturised probe. However, our final prototype constructed with four high purity silver made electrodes showed a good linearity (R 2 ¼ 0.999) in diluted saline solution measurements over a wide conductivity range (0.25-8 mS/cm), which covers well the range of values for the different biological tissues. Moreover, our data show that high reproducibility of the manufacturing and measurement is one important merit in the present 3D printed probe. However, further studies are needed to clarify the importance of fixed pressure especially when the tetrapolar 3D printed probe is used as a hand-held apparatus.

Novel 3D printed probe for bioimpedance spectroscopic measurement of oral mucosa: design and testing with ex vivo porcine oral tissues

“…In our previous studies, we found that designing a successful 3D printed probe for BIS measurements is a challenging task [3], and we faced similar challenges in this study. Selecting proper electrode materials for the newly designed probes was crucial (table 1).…”

“…In BIS, a weak alternating current is injected through a sample, e.g. human tissue, and, as an outcome, the impedance magnitude and phase are determined for each frequency point [3]. There has been an abundance of research and implementation of the BIS technique to various biomedical applications.…”

“…It has also been found to be an affordable solution to investigate pathological tissue alterations such as skin cancer [6] and breast cancer [7]. Despite this, attempts to assess oral mucosa health status or oral mucosal diseases by using BIS have been rare [3,[8][9][10]. Albeit rare, these studies have provided an encouraging sign that BIS could provide an easy, non-invasive way to assess the health of oral mucosal tissues.…”

“…To date, mainly custom-machined sensors have been used in BIS studies of oral mucosa, and manufacturing issues related to commercialization and clinical use have not yet been considered [10]. To take a step forward, we observed in our previous study [9] that three-dimensional (3D) printing could be a viable solution to construct innovative sensors for oral mucosal characterization and diagnostics of oral diseases, as this technique is already commercially available for many biomedical applications [3,14]. However, developing a fully 3D printed probe (i.e.…”

Bioimpedance Sensors: A Tutorial

“…Such elastomers can be modified or synthesized to demonstrate self-healing properties or good skin adhesion [147], [148]. Printing methods commonly used include inkjet [149], [150], screen [151], stencil, molding [140], [141] and extrusion-based (that we have been exploring in our Centre due to their simplicity) [152]- [154] and other 3D printing technologies [155], [156], as well as roll-to-roll contact printing approaches, such as gravure, flexographic printing [11] and transfer printing methods. Another interesting and very promising approach that we have been exploring is laserinduced graphitization of polyimide films and the transfer of the conductive structures on elastomers [157]- [159].…”