I. Core Research Summary

• A conductive composite system of a flowable, reversible gel

A 1:1 block copolymer is dissolved in hexadecane to form a microgel matrix, into which silver‑coated micron-sized particles are incorporated. Upon standing, the material solidifies; under shear, it becomes flowable, and upon removal of the external force, it rapidly re‑establishes its structure. The particles remain uniformly dispersed over long periods without settling, and the system exhibits a reversible electro‑responsive behavior upon cycling.

• Extremely strong electrical conductivity anisotropy, with electrical conductivity in the parallel direction increased by a factor of 100.

Two electrode configurations were designed: one with the electric field oriented perpendicular to the shear flow, and the other with the electric field aligned parallel to the shear flow. In the perpendicular configuration, electrical conductivity was relatively low; when the shear flow was aligned with the electric field, silver particles became preferentially oriented, forming continuous conductive pathways, resulting in a two-order-of-magnitude increase in conductivity. Moreover, the conductivity varied linearly with the shear rate according to a power-law relationship.

• Linear reversible rate-type electromechanical response

Electrical conductivity is strictly positively correlated with shear rate, and the loading–unloading shear signals exhibit no hysteresis, enabling direct differentiation between slow micro‑slip and high‑speed impact events, thereby overcoming the limitation of conventional strain sensors that can only measure total deformation.

• Custom radial interdigitated test electrode for aerosol spraying

Maskless digital printing of micron-scale annular interdigitated electrodes, compatible with the rheometer’s disk‑on‑disk testing platform, enables precise detection of conductivity changes arising from the microscale particle alignment under a parallel‑flow electric field; post‑high‑temperature sintering, the electrodes exhibit stable impedance.

• The microscopic directed transport mechanism has been fully elucidated.

In high Weissenberg number gel systems, shear-induced alignment of silver nanoparticles along the flow direction leads to a substantial increase in particle–particle contacts and the formation of continuous electronic delocalization pathways; the viscoelasticity of the gel serves as the fundamental basis for achieving reversible, directional particle organization.

II. Complete Preparation Process for Aerosol-Sprayed Electrodes

(1) Preparation Process

• Plasma cleaning of polyimide (Kapton) films enhances the adhesion of silver ink.
• Commercial silver nanoparticle ink is diluted with deionized water and terpineol, followed by ultrasonic dispersion to eliminate agglomeration.
• Aerosol Jet 200 system, with an atomization power of 0.45 mA, a nitrogen sheath gas flow rate of 40 sccm, a carrier gas flow rate of 15 sccm, and a 200 μm ceramic nozzle;
• At a constant printing speed of 6 mm/s, a custom 25-mm radial annular interdigitated electrode was fabricated, with a single-channel line width of approximately 40 μm.
• Pre-drying at 80°C, followed by sintering in a tube furnace at 200°C for 1 hour to remove organic additives and reduce electrode contact resistance.
• The electrode sheet is fixed to the rheometer base, and an AgMS gel composite material is loaded to perform simultaneous rheological–electrical measurements.

(II) Five Core Advantages of Aerosol-Based Processes (Comparison with Lithography and Inkjet)

• Customizable irregular-shaped annular radial interdigital electrodes

Lithography supports only standard linear arrays, whereas aerosol‑based CAD enables free‑form design, with a rheometer that accommodates circular interdigitated electrodes, making it well suited for specialized rheological‑electric field coupling characterization scenarios.

• Micron‑scale fine lines with precisely controllable electrode gaps.

Stable printing of 40-μm conductive traces with uniform interdigitated gaps ensures that even subtle changes in electrical conductivity can be accurately detected, thereby improving the test signal-to-noise ratio.

• Low-temperature, short-process molding; no damage to the PI flexible substrate.

Heat treatment up to 200°C does not compromise the flexibility or insulating properties of the polyimide film, making it compatible with all flexible sensing substrates.

• Maskless Rapid Iteration of Electrode Configurations

By revising the drawings for both the parallel and perpendicular electrode configurations of the electric field, two sets of samples can be fabricated in a matter of hours, significantly shortening the cycle time for mechanistic comparative experiments.

• Localized deposition saves the precious metal silver.

Conductive ink is deposited only in the electrode pattern areas, whereas full‑area evaporation or spin coating results in significant material waste; thus, small‑batch R&D in the lab is more cost‑effective.

III. Five Key Technological Innovations

Innovative, rate-responsive, flowable soft semiconductor: a completely new system

Innovation 2: A Novel Mechanism of Electric-Field–Shear Coupling in Anisotropic Conductive Materials

Innovation 3: Aerosol Jet Custom Rheology-Specific Annular Interdigitated Electrode

Innovative 4 Highly Reversible Dynamic Particle-Based Conductive Network

Innovation 5: Distinguishing the Static Strain/Dynamic Rate Dual-Sensing Paradigm

IV. Current Industry Challenges and Corresponding Solutions for Overcoming Them

Challenge 1: Traditional strain sensors only measure deformation and cannot distinguish between fast and slow motion.

Challenge 2: After cycling, filler agglomeration and sedimentation in conductive composites lead to signal drift.

Challenge 3: Lack of a specialized parallel‑plate electrode suitable for rheological testing.

Challenge 4: Lithography struggles to fabricate non-standard circular or irregular-shaped electrodes, resulting in high mask‑making costs and long production cycles.

Challenge 5: Ordinary conductive elastomers exhibit severe nonlinearity and hysteresis in their electrical signals.

V. Future Diversified Industrial Application Scenarios

1 Bionic Soft-Robot Tactile Skin

2. Wear the human motion monitoring patch

3 Bionic Muscle Spindle Physiological Sensing Element

4 Industrial Flexible Dynamic Pressure Sensing Array

5. Rheology in Higher Education – Electrical Coupling R&D Platform

Figure 1. Rheological response of swollen SEB–SEPS copolymer assemblies and AgMS‑particle‑containing composites. A) Rheological behavior of a 1:1 SEB:SEPS blend in hexadecane: liquid-phase viscosity data (represented by circles) are fitted to the modified Krieger–Dougherty equation shown as the black dashed line; viscosity values obtained from steady‑state flow curves are marked with solid circles, while those from frequency‑dependent small‑amplitude oscillatory shear tests are indicated by hollow circles; the storage modulus of the pure gel (triangular markers) is used to determine the liquid–solid transition point via power-law fitting (the black solid line denotes 24.3 mg·mL⁻¹). The inset shows a stirring rod suspended in a pure MG solution. B) Flow‑scan curves of the relative viscosity (𝜂r) of AgMS in an organic gel and in AR200 silicone oil: suspension viscosity data are normalized against the viscosity of silicone oil, whereas organic‑gel data are normalized against the viscosity of hexadecane. The AgMS–MG sample (upper panel) exhibits yield‑stress behavior, while the AgMS–oil sample displays Newtonian rheological response and spreads uniformly along the inclined scraper surface (lower panel).

Figure 2. Electrical behavior of the AgMS–MG composite under an electric field perpendicular to the flow direction. A) Schematic of the rheo‑electro‑geometric setup on an Ares G2 rheometer: two 25‑mm parallel plates are electrically connected via conductive leads, generating an electric field (⇀E⊥) perpendicular to the particle motion direction (or parallel to the gradient direction). B) The stepwise increase and decrease of the γ value at 180‑second intervals demonstrates that the measured electrical signal varies proportionally and reversibly with the flow rate. C) For the AgMS–MG sample containing 30% silver, the frequency‑dependent AC conductivity, corrected for background effects, as a function of both the AC frequency and the γ value. D) Scaling relationship between the steady‑state conductivity plateau in the low‑frequency regime and the γ value; the curve is fitted to a power-law distribution (shown by the dashed line), with the power-law exponent indicated in the figure. Error bars are calculated from the average σ over the <50 Hz frequency range, representing one standard deviation of the mean.

Figure 3 shows the comparative results of the electrical transport properties of MG suspensions and the oil phase, normalized to the reference conductivity σ0, for each set of test parameters γ and ϕ (with the corresponding dispersed phase indicated in the superscript). As the volume fraction ϕ increases, the AgMS–MG conductivity measured under an electric field applied along the gradient exhibits a stronger inverse dependence on γ; the red dashed line corresponds to a conductivity ratio of unity. The inset illustrates the electrode configuration (in orange) and the electric field distribution lines along the gradient direction (in red), relative to the shear field (in navy blue).

Figure 4. Investigation of the electronic transport properties of AgMS materials along the flow direction. A) Photograph showing the electrode configuration on the DHR rheometer, with the electrodes aligned in the flow direction; the inset illustrates the electric field (red), denoted by →E‖, which is parallel to the shear‑field direction (navy blue). B) DC current–response curves for a 30 vol% AgMS–MG sample under a constant 1 V bias; sequential increases and decreases in γ at 180‑second intervals reveal that the measured electrical signal at this electrode varies proportionally and reversibly with the shear rate. C) Shear‑dependent σ0 curves are plotted separately for 25 vol%, 30 vol%, and 35 vol% AgMS–MG composites, with power‑law relationships fitted using corresponding dashed lines. D) Shear‑dependent σ0 curves are presented for 25 vol%, 30 vol%, and 35 vol% AgMS–oil suspensions, displayed on a double‑logarithmic scale and fitted with exponential trends via dashed lines; the inset shows the same data on a log–linear plot to emphasize the distinct scaling relationship with γ.

Figure 5. Electrical transport analysis of AgMS–MG samples under different electric field orientations. A) In the AgMS fluid suspension, the ratio of the σ0 value measured with electrodes aligned along the flow direction (denoted by ∥) to that measured with electrodes oriented perpendicular to the gradient (denoted by ⊥), as a function of γ; the red dashed line indicates the case where the ratio equals 1. B) In the AgMS–MG composite, the ratio of the σ0 value measured with parallel electrodes to that measured with gradient‑oriented electrodes, as a function of γ. C) Schematic illustrating the electron transport mechanism in a viscoelastic medium, driven by enhanced AgMS alignment under an edge‑field: the flow field is denoted by →u, and the electric field by →E∥.