Abstract
Implantable neural probes are widely used to record and stimulate neural activities. These probes should be stiff enough for insertion. However, it should also be flexible to minimize tissue damage after insertion. Therefore, having dynamic control of the neural probe shank flexibility will be useful. For the first time, we have successfully fabricated flexible neural probes with embedded microfluidic channels for dynamic control of neural probe stiffness by controlling fluidic pressure in the channels. The present hybrid neural probes consisted of polydimethylsiloxane (PDMS) and polyimide (PI) layers could provide the required stiffness for insertion and flexibility during operation. The PDMS channels were fabricated by reversal imprint using a silicon mold and bonded to a PI layer to form the embedded channels in the neural probe. The probe shape was patterned using an oxygen plasma generated by an inductively coupled plasma etching system. The critical buckling force of PDMS/PI neural probes could be tuned from 0.25–1.25 mN depending on the applied fluidic pressure in the microchannels and these probes were successfully inserted into a 0.6% agarose gel that mimicked the stiffness of the brain tissue. Polymer-based neural probes are typically more flexible than conventional metal wire-based probes, and they could potentially provide less tissue damage after implantation.
Highlights
Implantable neural probes are widely used to record and stimulate neural activities
The channel width and fluidic pressure in the channels determined the flexibility of the neural probes, which could be optimized for implantation and reducing tissue damage
The displacement for the commonly used Ni/Cr and Cu wire probes were 3.21 and 0.35 mm, respectively. These results showed that the polymer-based neural probes were more flexible than the metal wire probes, which had the advantages of inducing less tissue damage due to brain micro-motions
Summary
Implantable neural probes are widely used to record and stimulate neural activities. These neural probes have been implanted into different tissues (e.g. brain, eye, and ear). In recent years [1,2,3,4,5], biocompatible polymer-based neural probes have been showed to be promising for neural prosthetics Different biocompatible polymers such as polydimethylsiloxane (PDMS) [6], parylene-C [7], liquid crystal polymer (LCP) [8], SU-8 [9,10,11], and polyimide (PI) [12,13,14] have been studied extensively as flexible neural probes to reduce human body responses after implantation [15,16,17,18]. Due to the high flexibility of PDMS, these neural probes were difficult
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