Advancements in fabrication process of microelectrode array for a retinal prosthesis using Liquid Crystal Polymer (LCP)

Abstract

Liquid Crystal Polymer (LCP) has been considered as an alternative biomaterial for implantable biomedical devices primarily for its low moisture absorption rate compared with conventional polymers such as polyimide, parylene and silicone elastomers. A novel retinal prosthetic device based on monolithic encapsulation of LCP is being developed in which entire neural stimulation circuitries are integrated into a thin and eye-conformable structure. Micromachining techniques for fabrication of a LCP retinal electrode array have been previously reported. In this research, however, for being used as a part of the LCP-based retinal implant, we developed advanced fabrication process of LCP retinal electrode through new approaches such as electroplating and laser-machining in order to achieve higher mechanical robustness, long-term reliability and flexibility. Thickened metal tracks could contribute to higher mechanical strength as well as higher long-term reliability when combined with laser-ablation process by allowing high-pressure lamination. Laser-thinning technique could improve the flexibility of LCP electrode.

Investigation of Surgical Techniques for Optimization of Long-Term Outcomes of LCP-Based Retinal Prosthesis Implantation

“…Additionally, we realized a further reduction of electrode array thickness, to 30 μm, by means of an advanced fabrication process such as laser-machining. 13 Furthermore, the long-term reliability of our device, achieved through adequate hermetic sealing, has already been established in a previous report. 8 …”

“… 11 The electrode array, as formed by a laser-thinning process, has a thickness of 30 μm. 11 , 13 The maximal width of electrode array was 3 mm. The transition part is deflected to connect the array with the package.…”

Advances in retinal prosthesis systems

“…Development is underway for novel biocompatible materials, such as laser-microstructured diamond electrode arrays, with greater longevity and chemical stability, 104 or liquid crystal polymers that are also ultra-thin, lightweight, and deformable. 105 In addition, the field of tissue electronics, concerned with the development of organic conductive and semi-conductive polymers, is emerging as an alternative to inorganic systems. Initial animal models have demonstrated efficacy, and it is postulated that the graded modulation of neurotransmitter release afforded via an organic array may create a more physiological interaction with the neuronal tissue, potentially enhancing the resultant spatial resolution.…”

Non‐hermetic packaging of biomedical microsystems from a materials perspective: A review

“…A monolithic system can be implemented by using LCP as the substrate for electrodes and interconnects as well as the encapsulating material (Lee et al, 2011), (Park et al, 2016), (Jeong et al, 2015). Therefore, LCP-based systems exhibit much higher long-term reliability, while maintaining the attributes of conventional polymer-based systems such as thinness, flexibility and compatibility with conventional fabrication procedures (Ha et al, 2010), (Chen et al, 2006;Jeong et al, 2015;Park et al, 2016), (Wang et al, 2003), (Jeong et al, 2012(Jeong et al, , 2013Lee, Seo, et al, 2009). However, LCP bonding requires a higher temperature (~285°C) (Jeong et al, 2015), than many packaged components can withstand.…”