Browsing by Author "Rihani, Rashed T."
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Item Liquid Crystal Elastomers as a Material for Neural Interfaces(2020-08) Rihani, Rashed T.; Pancrazio, JosephImplantable microelectrode development aims to enable functional restoration in patients who suffer paralysis, strokes, limb loss, or neurodegenerative disease. However, the chronic reliability of such neural interfaces is compromised, in part, by the body’s own foreign body response (FBR), leading to localized astrogliosis and fibrotic encapsulation of the device. These factors can lead to accelerated mechanical/electrical device failure and/or neuronal dieback at the site of implantation. The use of polymer substrates for neural interfaces has gained traction due to advantages such as mechanical flexibility and compliancy, which have been shown to reduce FBR-induced encapsulation when compared to the current state-of-the-art substrates (i.e., silicon). Liquid Crystal Elastomers (LCEs), a subclass of liquid crystal polymers (LCPs), exhibit a low modulus and can be fabricated into shapes which exhibit a high degree of flexibility. Furthermore, this class of polymers can be molecularly aligned to enable programmable and reversible shape change when exposed to a stimulus such as heat, light, or specific solvent. This approach potentially enables the controlled deployment of small recording or stimulation sites to regions beyond that of the FBR induced encapsulation (50 – 100 µm). The overarching goal of this project is to demonstrate the feasibility of using LCE-based implantable electrode arrays in chronic cortical recording applications. First, we evaluate cytotoxicity, functional neurotoxicity, and manufacturability of LCE as a substrate material for novel neural interfaces in vitro. Second, we evaluate the electrochemical stability of LCE as an insulating substrate in vitro. Finally, we evaluate the electrochemical stability and recording capability of LCE as an insulating substrate and deployable device in vivo.Item Responsive, 3d Electronics Enabled by Liquid Crystal Elastomer Substrates(American Chemical Society, 2019-05-09) Kim, Hyun; Gibson, J.; Maeng, Jimin; Saed, Mohand O.; Pimentel, K.; Rihani, Rashed T.; Pancrazio, Joseph J.; Georgakopoulos, S. V.; Ware, Taylor H.; 0000-0001-7996-7393 (Ware, TH); Kim, Hyun; Maeng, Jimin; Saed, Mohand O.; Rihani, Rashed T.; Pancrazio, Joseph J.; Ware, Taylor H.Traditional electronic devices are rigid, planar, and mechanically static. The combination of traditional electronic materials and responsive polymer substrates is of significant interest to provide opportunities to replace conventional electronic devices with stretchable, 3D, and responsive electronics. Liquid crystal elastomers (LCEs) are well suited to function as such dynamic substrates because of their large strain, reversible stimulus response that can be controlled through directed self-assembly of molecular order. Here, we discuss using LCEs as substrates for electronic devices that are flat during processing but then morph into controlled 3D structures. We design and demonstrate processes for a variety of electronic devices on LCEs including deformation-tolerant conducting traces and capacitors and cold temperature-responsive antennas. For example, patterning twisted nematic orientation within the substrate can be used to create helical electronic devices that stretch up to 100% with less than 2% change in resistance or capacitance. Moreover, we discuss self-morphing LCE antennas which can dynamically change the operating frequency from 2.7 GHz (room temperature) to 3.3 GHz (-65 °C). We envision applications for these 3D, responsive devices in wearable or implantable electronics and in cold-chain monitoring radio frequency identification sensors. ©2019 American Chemical Society.