This paper presents the implementation of a batteryless CMOS SoC with low voltage pulsed radio-frequency (PRF) stimulation. This implantable SoC uses 402 MHz command signals following the medical implanted communication system (MICS) standard and a low frequency (1 MHz) for RF power transmission. A body floating type rectifier achieves 84% voltage conversion ratio. A bi-phasic pulse train of 1.4 V and 500 kHz is delivered by a PRF driver circuit. The PRF parameters include pulse duration, pulse frequency and repetition rate, which are controllable via 402 MHz RF receiver. The minimal required 3 V RF Vin and 2.2 V VDDr is achieved at 18 mm gap. The SoC chip is fabricated in a 0.35 μm CMOS process and mounted on a PCB with a flexible spiral antenna. The packaged PRF SoC was implanted into rats for the animal study. Von Frey was applied to test the mechanical allodynia in a blinded manner. This work has successfully demonstrated that implanted CMOS SoC stimulating DRG with 1.4 V, 500 kHz PRF could significantly reduce spinal nerve ligation (SNL) induced mechanical allodynia for 3-7 days.

Low-voltage-driven organic field-effect transistors (OFETs) with an organic polymer p-type semiconductor poly­(2,5-bis­(3-alkylthiophen-2-yl) thieno­[3,2-b] thiophene) (PBTTT-C14) as the active layer were explored for the processing and crystallization of polymer semiconductors whose opto-electronic properties critically depend on the microstructure. Here, we report polymer crystallization from processed hexamethylbenzene (HMB)/PBTTT-C14 mixtures using a thermal gradient system to yield fiber-like crystals with up to 0.8 μm in width and to fabricate crystalline PBTTT-C14-based OFETs. In the thermal gradient system, the HMB separated from the HMB/PBTTT-C14 mixtures and crystallized along the samples’ moving direction. The crystals’ physical properties characterized by in situ atomic force microscopy and Raman spectroscopy at different temperatures revealed that the HMB-processed PBTTT-C14 thin film can improve the microstructure and achieve a directionally crystalline structure. These results combined with theoretical calculations show a high degree of π-stacking within the crystalline PBTTT-C14 (c-PBTTT-C14) crystal. c-PBTTT-C14 has good crystallinity, which enhances the intra- and intermolecular transmission of electrons. Whether in a nitrogen-filled glovebox or in the atmosphere, the electrical performances of the c-PBTTT-C14-based OFET had a remarkable increase compared with those of the spin-coated PBTTT-C14-based OFET. This phenomenon was also observed in the crystalline P3HT-based OFET fabricated by the same thermal gradient system.

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In this study, a high-K material, aluminum oxide (AlOx), as the dielectric of organic field-effect transistors (OFETs) was used to reduce the threshold and operating voltages, while focusing on achieving high-electrical-stability OFETs and retention in OFET-based memory devices. To achieve this, we modified the gate dielectric of OFETs using polyimide (PI) with different solid contents to tune the properties and reduce the trap state density of the gate dielectric, leading to controllable stability in the N, N’-ditridecylperylene-3,4,9,10-tetracarboxylic diimide (PTCDI-C13)-based OFETs. Thus, gate field-induced stress can be compensated for by the carriers accumulated due to the dipole field created by electric dipoles within the PI layer, thereby improving the OFET’s performance and stability. Moreover, if the OFET is modified by PI with different solid contents, it can operate more stably under fixed gate bias stress over time than the device with AlOx as the dielectric layer only can. Furthermore, the OFET-based memory devices with PI film showed good memory retention and durability. In summary, we successfully fabricated a low-voltage operating and stable OFET and an organic memory device in which the memory window has potential for industrial production.