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International Journal of Bioprinting Amphiphobic encap. for transient devices

The final polyanhydride film can be produced by repeatedly representative transient metal, was conducted. Cr with
moving the 3D printer’s substrate in the z-axis direction a thickness of 20 nm was used as an adhesion layer on a
(50 μm) after the unit layer of the dispensed precursor glass substrate using electron-beam (e-beam) deposition.
solution is cured. Subsequently, 300 nm of Mg was deposited on top of the Cr
layer using a similar process. Mg was patterned to have a
The chemicals 4PA, TTT, and BDT were mixed at a
molar ratio of 1:4:7 in a 10 mL vial, with 2,2-dimethoxy-2- serpentine resistor pattern using laser cutting and a PBTPA
layer was placed thereon to investigate the waterproofing
phenylacetophenone as the photoinitiator (a total mass of performance. Thereafter, the polydimethylsiloxane
0.5%), which was added to prepare a 1:4:7 PBTPA solution. (PDMS) well was fixed using epoxy to expose the PBTPA
The 1:1:2.5 PBTPA solution that was needed to create an area covering the serpentine Mg to deionized (DI) water.
amphiphobic structure was prepared similarly except for DI water was used to degrade the Mg pattern. The hole in
a change in the composition. The solution was pre-cured the PDMS well was covered with another PDMS layer to
under UV light at 365 nm to prevent the PBTPA solution prevent the evaporation of DI water. The resistance was
from flowing down on the substrate of the 3D printer. measured at the end of the Mg resistor connected to a Cu
After conducting the pre-curing process for approximately wire. The prepared test device was stored in an oven at 37°C
2 min, the 3D printing condition was optimized to expose and its resistance was measured once every few hours.
the 50-μm-thick PBTPA layers to UV light (365 nm)
for 5000 ms to form one unit layer. The entire 500-μm- A tensile test was conducted to obtain the stress–strain
thick PBTPA layer could be printed by repeating this curve of each sample group using a universal testing
procedure—dispensing 50 μm of the PBTPA solution and machine (UTM; UNITEST M1; Test One, Korea), and the
curing it for 5000 ms. strain, Young’s modulus, and toughness were calculated
accordingly. All 3D-printed samples for the tensile test
2.3. Preparation of screen-printed PBTPA were fabricated in accordance with the ASTM-D1708
The PBTPA solution for screen-printing was also produced standard (Figure S6, Supporting Information). The screen-
in the same manner as above, and it was pre-cured in a hood printed PBTPA was physically cut into the same standard
for more than a day to obtain a viscosity suitable for screen- using CAMEO 4 (Silhouette, USA).
printing. As a spacer on a glass substrate, 50-μm-thick
single-sided tape was deposited at intervals of approximately 2.6. Simulation
3 mm and stacked at two positions. The pre-cured PBTPA For the molecular dynamics (MD) simulations in this study,
solution was dropped using a disposable pipette and spread we utilized the NAMD 2.13 software, which is integrated
thinly using a razor as a applicator . The thin PBTPA within Discovery Studio. The simulations incorporated the
solution membrane was cured under 365 nm UV light for CHARMM force field for an accurate representation of the
approximately 20 min and then removed using a razor. molecular interactions. The simulations were executed on a
multicore system using Charm++ for parallel computation,
2.4. 3D printing of the amphiphobic enhancing its efficiency. Our model systems, representing
encapsulation layer amphiphobic and hydrophobic PBTPA structures, were
The 1:4:7 and 1:1:2.5 PBTPA solutions were produced as simulated over a period of 1000 ps to observe their
aforementioned, and both the solutions were pre-cured dynamic behavior and stability. The setup parameters for
for approximately 2 min. Under the specified thickness the simulations were selected to reflect realistic physical
requirements, 1:1:2.5 PBTPA and 1:4:7 PBTPA were conditions, with the CHARMM force field providing
stacked alternately in layers of 50 μm each. For example, the necessary potential functions for the interactions
in the case of 3P/150h1-100h2, 1:1:2.5, 1:4:7, and 1:1:2.5 between atoms. The simulation environment included
PBTPA were dispersed and cured three, four, and three explicit solvent models, and electrostatic interactions
times, respectively. were calculated using the Ewald summation method.
Bond lengths within the molecules were constrained
2.5. Characterization of the polyanhydride using the SHAKE algorithm, ensuring structural integrity
encapsulation layer throughout the simulation period.
To quantify the attenuation effect of conventional screen- Data from the simulations, specifically focusing on
printed PBTPA layers, light transmittance (T) was electrostatic energy stabilization and hydrogen bonding,
measured using an ultraviolet-visible-near-infrared (UV– were analyzed to evaluate the stability and interaction
vis-NIR) spectrometer (Agilent Technologies, USA).
patterns within the PBTPA structures. This analysis was
To investigate the waterproofing performance of used to understand the molecular basis of the effectiveness
3D-printed PBTPA, resistance monitoring of Mg, a of amphiphobic encapsulation.

Volume 10 Issue 5 (2024) 309 doi: 10.36922/ijb.3871