# Microfibrillated Cellulose Embedded with KCl as a Solid-Dopant Matrix into an Electrolyte-Gated Transistor

## TL;DR

This paper introduces a new solid-dopant matrix made of microfibrillated cellulose and potassium chloride for use in electrolyte-gated transistors, simplifying device design and improving performance.

## Contribution

The novel MFC:KCl matrix serves as both an electrolyte reservoir and ion anchor, eliminating the need for synthetic polymers.

## Key findings

- The MFC matrix retains water as effectively as traditional methods, with stable transistor operation and good current modulation.
- MFC:KCl reduces the electrochemical window and improves stability at higher gate voltages compared to KCl:H2O.
- The material achieves high transconductance and drain current, making it suitable for both field-effect and electrochemical transistors.

## Abstract

Electrolyte retention
in electrolyte-gated transistors (EGTs) is
typically achieved through viscous electrolytes or extra manufacturing
steps for the reservoir design. In this work, we present a multifunctional
solid-dopant matrix (SDM) composed of microfibrillated cellulose embedded
with potassium chloride (MFC:KCl), which simultaneously acts as an
electrolyte reservoir and provides ion anchoring that simplifies the
device architecture and processing. For comparison, four electrolyte
configurations were systematically investigated: (i) H2O (as a nonionic reference), (ii) MFC:H2O, (iii) KCl:H2O (as an ionic reference), and (iv) MFC:KCl:H2O.
In water-based transistors, the MFC matrix serves as a pure electrolyte
reservoir, showing water retention capability equivalent to the reference
device, characterized by an on/off current ratio of ∼102, a threshold voltage of −0.13 V, a maximum drain current
of ∼10–4 A, and a maximum transconductance
of ∼0.5 mS, operating within a stable electrochemical window.
In KCl–H2O-based transistors, the MFC:KCl material
demonstrates dual functionality: simultaneously (i) retaining the
electrolyte and (ii) compressing the operational electrochemical window
(−0.2 to +0.8 V in MFC:KCl:H2O vs −0.9 to
+1.0 V in KCl:H2O controls). This enables stable transistor
operation up to V
G ∼ −2
V while maintaining comparable current modulation (I
on/I
off ratios ∼ 103), against unstable operation of KCl:H2O electrolyte-based
devices. In addition, it presents a threshold voltage of −0.7
V, a maximum drain current of ∼10–3 A, and
a maximum transconductance of ∼ 3 × 102 mS.
This study reveals that MFC offers a versatile platform for both field-effect
and electrochemical transistors, aligning with green electronics initiatives
by avoiding synthetic polymers like polydimethylsiloxane (PDMS).