I. Core Research Summary

• One-step simultaneous atomization + in-situ electric-field polarization

Traditional piezoelectric materials require two processing steps—high-temperature sintering followed by high-pressure poling. In contrast, TEA aerosol printing enables nanoscale-confined crystallization and oriented dipole alignment during droplet flight, directly yielding a highly ordered β‑glycine piezoelectric phase in a single step, thereby boosting manufacturing efficiency by two orders of magnitude.

• Ultra‑strong piezoelectric output performance, surpassing that of conventional commercial piezoelectric materials.

The thin-film piezoelectric voltage coefficient g₃₃ is 190 × 10⁻³ V·m/N, with performance exceeding that of industrial PZT ceramics by an order of magnitude; the Curie temperature is 185°C, and its thermal stability surpasses that of mainstream piezoelectric polymers and ceramics such as PVDF and barium titanate.

• Highly Flexible Fully Biodegradable Composite Film

Both glycine and PVP are medical-grade, biosafety‑compliant materials. The film exhibits a significantly lower elastic modulus than pure glycine crystals and can be repeatedly bent. It dissolves rapidly in pure water within 30 seconds and undergoes complete biodegradation in soil within 2 hours, leaving no residual toxic substances.

• Subcutaneous ultrasonic wireless energy harvesting is stable and reliable.

Based on this thin film, an ultrasonic piezoelectric energy harvester (Gly-PUEH) was fabricated. Under 17-mm-thick porcine tissue, the output power density under ultrasonic excitation reaches 35 μW/cm², enabling stable operation of wireless temperature sensors and brain optogenetic LED stimulation modules.

• Excellent cellular biosafety

The fibroblasts cultured in the extract exhibited a survival rate close to that of the control group after 3 days, with no apparent cytotoxicity, making it suitable for short-term postoperative temporary implantation devices.

II. Complete Preparation Process and Unique Technological Advantages of Thermal‑Electrical Aerosol (TEA)

(1) Complete TEA Aerosol Printing Process

• Prepare a water-based bioink containing glycine and PVP, and stir until homogeneous.
• The device simultaneously applies a thermal field and an electrostatic atomization field, enabling the ink to form charged nano‑aerosol droplets.
• During the droplet‑flight stage, ordered β‑glycine nanocrystals precipitate via a nanoconfinement effect, while an applied DC electric field induces in situ directional polarization.
• A 60°C low-temperature substrate enables rapid solvent evaporation, while multilayer aerosol deposition yields a continuous piezoelectric thin film.
• Double-sided aerosol-printed silver conductive electrodes, encapsulated in PDMS, yield a flexible ultrasonic energy-harvesting device.

(II) Five Core Process Advantages (Compared with Spin Coating, Electrospinning, and Ceramic Sintering Processes)

• One-step integration of crystallization and polarization, eliminating the need for post-processing steps.

Traditional fabrication relies on molding and stepwise polarization, taking dozens of hours; in contrast, TEA aerosol printing enables simultaneous droplet flight, crystal orientation, and dipole polarization, yielding a high‑voltage electroactive material upon formation, with a printing speed of 10⁸ μm³/s—representing a hundredfold increase in efficiency.

• Produced throughout the entire process at low, gentle temperatures, ensuring that the bio‑ingredients retain their efficacy.

The maximum processing temperature is only 60°C; there is no high‑temperature ceramic sintering at over a thousand degrees, so amino acids and polymers do not undergo thermal decomposition, making it compatible with a wide range of biodegradable ink systems.

• Digital, maskless, large-area roll-to-roll mass production

An aerosol multi-nozzle array paired with a roll‑to‑roll substrate enables the continuous fabrication of large‑area piezoelectric thin films; custom device dimensions can be defined in CAD, supporting both small‑batch prototyping and scalable mass production.

• Precise control of crystal orientation at the nanoscale

By precisely tuning both the electric field and thermal field parameters, the β‑phase fraction and grain size can be controlled, yielding uniform piezoelectric performance in the thin films, with batch-to-batch consistency far superior to that achieved by conventional solution‑based self‑assembly.

• The bioink is highly compatible and environmentally friendly, containing no heavy metals.

It uses only amino acids and water-soluble polymers, contains no toxic inorganic fillers such as lead or titanium, and achieves extremely low material loss through on-demand aerosol deposition, resulting in low production costs.

III. Five Key Technological Innovations

Innovation 1: A Novel Formulation System for Thermoelectric-Aerosol (TEA) Co-Generation

Innovative 2-nm confined-stability β-glycine piezoelectric crystalline phase

Innovation 3: All-Bio‑Based Biodegradable Flexible Piezoelectric Composite System

Innovation 4: Subcutaneous Ultrasound-Based Remote Passive Power Supply Scheme

Innovative 5: Scalable Roll-to-Roll Aerosol Bio-Piezoelectric Manufacturing Platform

IV. Existing Process Challenges and Corresponding Solutions for Overcoming Them

Challenge 1: Conventional glycine-based materials readily undergo phase transitions at room temperature, leading to rapid degradation of their piezoelectric performance.

Challenge 2: Piezoelectric ceramics and PVDF are non-degradable; for short-term implantation, surgical removal is required.

Challenge 3: Traditional piezoelectric manufacturing involves a two-step process—sintering followed by polarization—which is time-consuming and costly.

Challenge 4: Pure glycine crystals are extremely brittle and cannot be adapted to flexible implantation applications.

Challenge 5: Inorganic piezoelectric materials contain heavy metals, posing a long-term bio-toxicity risk.

V. Future Diversified Industrial Application Scenarios

1. Temporary absorbable cardiac pacemaker implant

2. Optogenetic Wireless Implantable Probe for Brain Science

3. Wearable non-invasive physiological sensing patch

4. Piezoelectric Scaffolds for Cartilage/Bone Tissue Engineering

5. Single-use minimally invasive interventional sensing chip

Figure 1. TEA printing strategy. (A) Schematic illustration of the TEA method for fabricating natural piezoelectric biomaterials, based on (B) nanoscale confinement and (C) in-situ aerosol polarization techniques. (D) Schematic depicting the roll-to-roll deposition of conductive foil to form a piezoelectric biofilm. (E) SEM images showing the structural evolution from dispersed particles to aggregated clusters and finally to a fused thin film. (F) Photograph of a rolled glycine/PVP thin film. (G) The deposited glycine/PVP thin film exhibits excellent flexibility. (H) Performance comparison between conventional techniques and the TEA printing method in terms of fabrication speed and achievable film thickness.

Figure 2. Optimization of the TEA printing process. (A) Schematic illustration of the TEA printing mechanism based on electrohydrodynamic aerosol droplets. (B) XRD patterns of the samples: as‑deposited β‑glycine/PVP thin film (red curve), glycine/PVP film prepared under zero thermal field conditions (blue curve), glycine microcrystals fabricated by electrohydrodynamic focused printing (purple curve), α‑phase crystals formed under an excessively strong thermal field (dark red curve), and α‑phase crystals obtained by direct evaporation of a bulk glycine/PVP solution (black curve). W/ denotes the presence of a thermal field, while W/O indicates its absence. (C) Jetting distribution map plotted against dimensionless flow rate and dimensionless voltage. This figure quantitatively characterizes stable jetting regimes under various process parameters (gray region); the resulting phase states and grain sizes delineate nanoscale confinement zones and in situ polarization domains (orange region).

Figure 3. Mechanical properties, piezoelectric performance, thermal stability, and degradability of glycine/PVP thin films. (A) Elastic modulus (E) of glycine/PVP thin films prepared with varying glycine-to-PVP mixing ratios. (B) Comparison of the elastic modulus of as‑deposited glycine/PVP thin films with that of piezoelectric ceramics (PZT and BTO), piezoelectric polymers (PVDF), and pure glycine thin films. (C) Temperature dependence of the dielectric constant of as‑deposited glycine/PVP (1:1) thin films, measured at frequencies of 1 kHz, 10 kHz, 100 kHz, and 1 MHz. (D) In situ variable‑temperature XRD patterns of as‑deposited glycine/PVP (1:1) thin films. (E) Piezoelectric coefficient d₃₃ for glycine/PVP thin films with different compositional ratios. (F) Comparison of the longitudinal piezoelectric voltage coefficient g₃₃ of conventional piezoelectric materials with that of the glycine/PVP (1:1) thin film studied herein, as a function of the Curie temperature T_C. (G) Dissolution behavior of glycine/PVP (1:1) thin films in deionized water. (H) Biodegradability of glycine/PVP (1:1) thin films in moist soil.

Figure 4. Characterization of Gly‑PUEH in ex vivo porcine tissue. (A) Schematic illustration of an implantable Gly‑PUEH device enabling wireless ultrasonic energy transmission throughout the entire tissue. (B) Schematic and physical photograph of the Gly‑PUEH structure implanted approximately 1.7 cm beneath porcine tissue. (C) Finite-element simulation results showing the distribution of ultrasound‑induced piezoelectric potential within the Gly‑PUEH. (D and E) Waveforms of the open‑circuit voltage and short‑circuit current signals from the Gly‑PUEH. (F) Charging curve of a 33 μF capacitor and the corresponding transmitted signal. (G) Configuration of a wireless communication system comprising the Gly‑PUEH and a transmitter under ex vivo conditions. (H) Optical image demonstrating the photostimulation effect of a single LED illuminated by the Gly‑PUEH within a brain‑tissue model. (I) Cell viability assessment of myofibroblasts cultured in sample extracts, using the CCK‑8 assay (Gly: glycine‑coated film; Ag‑gly: silver‑coated glycine‑coated film). (J) Time‑dependent piezoelectric voltage output curve of the Gly‑PUEH.