NU 2020-016
INVENTORS Reem Rashid Robert Ciechowski Joanathan Rivnay*
SHORT DESCRIPTION Organic electrochemical transistor complementary inverter for the recording and amplification of biological signals
BACKGROUND The discovery of the transistor opened up the ability to control electron flow in a solid-state device, which ultimately led to the development of the integrated circuit, a foundational technology for electronic devices. Among the various types of transistors, organic electrochemical transistors (OECTs) have specifically gained attention for their use as effective switches and sensor devices that take advantage of bulk transport of ionic/electronic species in the active channel material and lead to high amplification. In particular, their characteristics make them suitable for biological applications. However, traditional OECTs have planar configurations which can impact both electrical properties and limit the form factor. Vertical OECTs (vOECTs) seem to have addressed these limitations, though the manufacturing of such transistors utilizes photolithography which can introduce capacitance issues.
ABSTRACT Complementary inverters have the potential to be used as low-power, high-gain pre-amplifiers but face compatibility issues with biological environments. For this reason, OECTs have gained attention for their biocompatibility, ease of fabrication, and high transduction efficiency. Current organic semiconducting materials have difficulty transporting both holes and electrons simultaneously thus p-type and n-type materials need to be patterned into separate channels. In many cases this leads to additional fabrication demands. In addition, even with ambipolar materials, lateral patterning of a complementary pair can take up valuable real estate on a bioelectronic probe. To address these short comings, Northwestern researchers have developed a new type of OECT-based complementary pair based on cofacial vOECTs. To achieve this construct, they use a laser ablasion method to cut a stack of metals and insulators, including a hydrophobic layer to pattern the dial vOECT channels. Their wiring is such that they share a common gate (the sensing environment electrolyte) but form a complementary inverter pair. Using an ambipolar material, they demonstrate a functioning inverter with gain of ~11. This same cofacial pair can be applied in a different configuration as a differential pair for biochemical sensing.
APPLICATIONS
ADVANTAGES
IP STATUS A US provisional application has been filed.