Laser-Induced Graphene-Polyimide Film Sensor for Simultaneous Lip Electromyography and Pressure Monitoring in Personalized Rehabilitation

Summary

This protocol describes fabrication, calibration, and use of a flexible PI/LIG sensor to synchronously measure OOM-EMG, lip-closing pressure, and intraoral pressure during standardized lip tasks, emphasizing reproducibility via acceptance criteria, moisture-mitigation encapsulation, device-specific calibration, standardized placement, synchronized acquisition, and predefined processing and QC rules.

Abstract

Simultaneous quantification of perioral muscle activation and lip-related pressures can support objective assessment of orofacial function, yet conventional measurements are commonly performed with separate sensors that are difficult to synchronize during dynamic tasks. Here, we present a reproducible protocol for synchronized recording of orbicularis oris electromyography (OOM-EMG), lip-closing pressure (LP), and intraoral pressure (IP) using a flexible polyimide (PI) film-based composite sensor with laser-induced graphene (LIG) electrodes and an integrated pressure-coupling pad. The protocol specifies laser patterning with prespecified electrical acceptance criteria, selective encapsulation intended for short-duration measurements, bench calibration for device-specific voltage-to-pressure conversion, standardized anatomical placement landmarks for perioral and intraoral interfaces, a task battery (lip closure, blowing, and sucking), synchronized acquisition requirements, and core signal-processing and trial-quality rules. Representative recordings in 120 healthy adults demonstrate synchronized multimodal capture under standardized conditions, with PI/LIG-derived EMG showing moderate association with conventional surface EMG (women r = 0.65; men r = 0.68) and LP strongly coupled with IP within the same task windows (r = 0.90). This method's article provides an end-to-end, replication-oriented workflow for multimodal perioral measurement in supervised research settings; validation in patient cohorts and durability under prolonged oral moisture exposure and repeated mechanical deformation should be evaluated in future studies.

Introduction

Lip muscles are fundamental to speech articulation, swallowing, facial expression, and oral competence. Neurological disorders, stroke, and maxillofacial interventions can disrupt these functions, leading to clinically meaningful limitations in communication and feeding and reducing quality of life¹. Objective quantification of perioral muscle activation together with force or pressure generation is therefore valuable for functional assessment and rehabilitation planning. In particular, synchronized measurement of orbicularis oris electromyography (OOM-EMG), lip-closing pressure (LP), and intraoral pressure (IP) offers complementary perspectives on how neural activation translates into task-relevant pressure production during behaviors commonly used in therapy and outcome tracking².

However, integrated acquisition of these signals remains technically and operationally challenging. In many laboratories and clinical research settings, EMG and pressure measurements are implemented as separate subsystems, increasing preparation burden and making time alignment more error-prone during short, dynamic tasks³. Perioral EMG is particularly vulnerable to motion artifacts and interface instability, and moisture from the perioral and oral environment can elevate baseline noise, reducing effective signal-to-noise ratio and complicating cross-session comparability⁴. Pressure measurements introduce additional sensitivities, as fixation and local contact mechanics can alter measured amplitudes, and rigid transducers may reduce tolerability during repeated trials or longer sessions⁵. Together, these constraints limit routine use of synchronized, task-aligned perioral EMG and lip-related pressure monitoring outside specialized workflows^6,7.

Flexible polyimide (PI) films provide a practical substrate for perioral sensing because they are thin, conformable, chemically stable, and widely used for biomedical interfaces. Laser-induced graphene (LIG) patterned directly on PI forms a porous conductive network that can function as a conformal electrode without bulky housings^8,9. Integrating LIG electrodes and a pressure-coupling structure on the same PI substrate enables co-located OOM-EMG recording and lip-surface pressure sensing while minimizing added mass at the lips. When combined with explicit fabrication acceptance criteria, moisture-mitigation encapsulation, standardized placement landmarks, and fixed task timing definitions, such integration can improve the reproducibility and interpretability of multimodal perioral recordings across operators and sites^10,11.

Here, we describe a reproducible protocol to fabricate, calibrate, and deploy a PI/LIG composite sensor for synchronized recording of OOM-EMG, LP, and IP during standardized lip tasks. The protocol emphasizes replication-oriented details spanning fabrication and quality acceptance checks, device-specific bench calibration for voltage-to-pressure conversion, standardized placement and hygiene procedures, synchronized acquisition requirements, and predefined signal-processing and trial-exclusion rules. Representative recordings in healthy adults are included to demonstrate short-session feasibility under standardized conditions, while patient validation and long-term durability under sustained oral moisture exposure and repeated mechanical deformation are positioned as priorities for future work rather than inferred from the present dataset¹².

Protocol

This study was approved and conducted in accordance with the ethical committee guidelines of Shanghai Jiao Tong University. Written informed consent was obtained from each participant before the study.

1. Ethics and consent

1. Obtain institutional ethics approval before enrollment, and record the protocol ID and approval date for reporting.
2. Obtain written informed consent from each participant. Document the consent form version and date.

2. Fabrication of the PI/LIG sensing elements

1. Cut polyimide film to the target footprint. Use a film thickness of 25 µm or 50 µm. Verify thickness with a micrometer (tolerance ±1 µm) and record the lot number.
   NOTE: Keep thickness consistent within each batch. If both thicknesses are used, calibrate each device individually (step 4.2) and do not mix calibration coefficients across devices.
2. Pattern laser-induced graphene on the polyimide film to form two orbicularis oris EMG electrodes and a central pressure-coupling pad. For a CO₂ laser (10.6 µm), set the average power at the work surface to 4.0 W, set the scan speed to 150 mm/s, set the hatch spacing to 50 µm (approximately 508 dpi), apply two passes, apply +1.0 mm defocus, and use a single-direction hatch¹³.
   1. Accept only devices meeting all criteria: (i) visually uniform matte-black LIG, (ii) sheet resistance 20-60 Ω/□ by four-point probe, (iii) within-pad coefficient of variation ≤15% across predefined measurement points, and (iv) no pinholes larger than 100 µm under approximately 10× inspection¹⁴.
   2. If a different laser system is used, tune patterning settings until the acceptance criteria in step 2.2.1 are satisfied, and record all laser settings used¹⁵.
      NOTE: Summarize laser patterning parameters and batch-level acceptance criteria in Table 1.
3. Rinse the patterned film under deionized water for 30 s without rubbing the LIG surface. Rinse under isopropanol for 30 s. Air-dry for at least 10 min in a dust-free enclosure.
4. Encapsulate all non-contact regions to mitigate moisture ingress and stabilize mechanical handling. Apply a medical-grade polyurethane or polydimethylsiloxane (PDMS) layer to all regions that will not directly contact the skin or bear lip-surface loading, targeting a dry thickness of 10-30 µm.
   1. Mask the EMG contact pads and the central pressure pad before coating so that these sensing interfaces remain fully exposed after curing. After curing, visually confirm a continuous encapsulation film with clean, sharply defined boundaries around the exposed pads and no pinholes, pooling, or edge lift at strain-concentrating corners (see Figure 1E-F for representative fabricated and selectively encapsulated devices).
   2. Add strain relief at the lead-pad transition and route leads such that the minimum bend radius is ≥3 mm to reduce stress concentration during handling and placement¹⁶.
   3. If PDMS is used, prepare and cure the encapsulation consistently within each batch. Degas PDMS prior to coating to remove trapped bubbles, apply the coating evenly, and cure at 70 °C for 30 min. After curing, re-inspect the exposed-pad boundaries to confirm that no residual PDMS bridges across the sensing areas.
      NOTE: Use one encapsulation material consistently within a batch whenever possible. If encapsulation materials change between batches, repeat the acceptance checks in steps 2.6 and 4.2 for each batch.
5. (Optional) Laminate a compliant diaphragm over the pressure pad to improve force transfer. Laminate a silicone diaphragm (100-200 µm) centered over the pressure pad and secure it using adhesive applied only to the perimeter. Ensure that no adhesive occludes the sensing area and that the diaphragm surface remains flat without wrinkles. Inspect under approximately 10× magnification and reject devices with visible occlusion or misalignment.
   NOTE: If a diaphragm is used, apply it consistently across participants within a sturdy arm and document diaphragm thickness and fixation method.
6. Store finished devices under controlled humidity and verify pre-use electrical stability. Store devices in a desiccator at 20-25 °C and ≤30% relative humidity for up to 7 days before use.
   1. Re-measure sheet resistance immediately before use at the same predefined locations used after fabrication. Accept devices with ≤5% drift relative to the post-fabrication value, and exclude devices exceeding this threshold from participant testing¹⁷.
7. Short-term humidity challenge for encapsulation integrity (performed)
   1. Place each device in a sealed humidity chamber at 85 ± 5% relative humidity and 25 ± 2 °C for 60 min, ensuring that the exposed EMG pads and pressure pad remain uncovered¹⁸.
   2. Remove the device and equilibrate at ambient conditions (20-25 °C, 40-60% RH) for 10 min.
   3. Re-measure sheet resistance at the same predefined locations used in step 2.2.1.
   4. Define pass criteria as sheet-resistance drift ≤10% relative to the post-fabrication value and no visible delamination, blistering, or cracking¹⁹.
      NOTE: In this study, the humidity challenge was performed on n = 12 devices across 2 batches, yielding a mean drift of 3.9 ± 1.8% (range 1.1 to 8.6%) with 12/12 devices meeting the pass criteria (Supplementary Table 1).
8. Cyclic bending durability test for LIG fragility and drift (performed)
   1. Mount each device on a bending jig, applying repeated bending to a fixed radius of 5 mm, with the patterned region centered on the bend axis.
   2. Apply 1,000 cycles at 1 Hz (one bend-release per second)²⁰.
   3. Measure sheet resistance at baseline (0 cycles) and after 100, 500, and 1,000 cycles.
   4. Define pass criteria as: (i) drift ≤15% at the final cycle count, (ii) no sudden resistance jumps >30% between checkpoints, and (iii) no visible cracking or delamination under approximately 10× inspection²¹.
      NOTE: In this study, the bending test was performed on n = 12 devices, and the final-cycle drift was 6.2 ± 3.4% (range 1.4 to 13.9%). No abrupt resistance jumps were observed in 12/12 devices, and 12/12 devices met all pass criteria (Supplementary Table 1).
   5. If any device fails the criteria, re-fabricate the LIG pattern, revise encapsulation coverage at strain-concentrating edges, and repeat the test using the same jig radius and frequency.
9. Simulated saliva exposure and insulation-leak check (performed)
   1. Prepare a simulated saliva solution at pH 6.8-7.2 and equilibrate to 37 °C.
   2. Protect the exposed EMG pads and pressure pad with a removable mask so that only encapsulated regions are challenged. Immerse the device at 37 °C for 60 min with gentle agitation (e.g., 60 rpm)²².
   3. Remove the device, rinse with deionized water for 10 s, and air-dry for 10 min at ambient conditions.
   4. Measure inter-lead insulation resistance at 10 VDC and record the value.
   5. Define pass criteria as: (i) insulation resistance >20 MΩ, (ii) sheet resistance drift ≤10% relative to baseline, and (iii) no signal dropout or intermittent contact during a 30 s bench recording²³.
      NOTE: In this study, simulated saliva exposure was performed on n = 12 devices. The minimum post-exposure insulation resistance was 64 MΩ, and sheet-resistance drift was 4.6 ± 2.1% (range 0.9 to 9.2%). All pass criteria were met by 12/12 devices (Supplementary Table 1). If insulation resistance decreases below threshold, do not use the device on participants. Re-encapsulate suspected ingress regions and repeat steps 2.9.1-2.9.6. Summarize all chamber setpoints, bending parameters, exposure conditions, sample sizes, and drift outcomes as batch-level metadata in Supplementary Table 1. If needed, provide per-device drift curves in Supplementary Table 2.

3. Assembling the module and reference channels

1. Attach flexible leads to the LIG pads using solder or conductive epoxy. If conductive epoxy is used, cure at 80 °C for 30 min.
   1. Verify end-to-end lead resistance <50 Ω. Route the leads to a shielded connector and secure the cable to minimize tugging at the pad interface.
2. Prepare reference channels.
   1. Prepare conventional surface EMG electrodes for orbicularis oris recording.
   2. Prepare an intraoral pressure reference channel using a manometry line (outer diameter 2-3 mm) and a pressure transducer (range ±20 kPa; resolution ≤0.1 kPa).
3. Confirm electrical continuity and insulation. Measure inter-lead insulation resistance >20 MΩ at 10 VDC. Document channel mapping.

4. Bench calibration and safety checks

1. Measure electrode-path impedance at 100 Hz using either (i) a standardized skin-contact check during setup or (ii) a gel phantom used consistently across devices. Accept channels with impedance <10 kΩ and record impedance values.
   1. (Recommended check) Re-measure electrode-skin impedance after the task battery and repeat placement if impedance increases by >20% relative to baseline.
2. Calibrate the pressure pad and intraoral pressure line using known pressures from 0 to 10 kPa.
   1. Apply pressures at 0, 1, 2, 3, 4, 5, 7.5, and 10 kPa with a 3 s dwell at each step. Repeat the sequence three times before participant testing and once after testing.
   2. If using a water column, convert height h (cmH₂O) to kPa using: kPa = 0.0980665 × h.
   3. Fit a linear model kPa = a·V + b. Accept calibrations meeting all criteria: R² ≥0.995, maximum absolute residual ≤0.2 kPa, and pre- vs post-experiment slope drift ≤1% of full scale.
   4. Save device-specific calibration coefficients for offline voltage-to-kPa conversion.
      NOTE: If calibration criteria are not met, do not proceed to participant testing. Rebuild or re-encapsulate the device and repeat calibration. Present representative calibration curves together with the device overview in Figure 1.
3. Disinfect all skin-contact parts using 70% isopropyl alcohol. Apply single-use or high-level disinfection for intraoral parts according to institutional policy. Record disinfectant and dwell time.
4. Round and encapsulate exposed LIG edges to avoid abrasion. Confirm the absence of sharp edges using a fingertip snag test.
   NOTE: If snagging occurs, re-encapsulate immediately or replace the device.

5. Preparing participants and placing sensors

1. Screen healthy adults and record demographics as specified in Table 2. Exclude individuals with active oral lesions or acute respiratory illness.
2. Seat the participant upright with back support, ~90° hip flexion, and a neutral chin position.
3. Clean the upper vermilion border with 70% alcohol wipes. Allow the skin to air-dry for at least 30 s.
4. Place the PI/LIG EMG electrodes along the superior orbicularis oris.
   1. Align the electrode pair parallel to the upper vermilion border and center the array on the facial midline. Set the inter-electrode center-to-center distance to 11 ± 1 mm and ensure both contact pads lie flat without wrinkling or edge lift.
   2. Place the reference electrode on the ipsilateral cheek over a low-motion region and place the ground electrode on the forearm.
   3. Verify stable contact by confirming that the electrode-skin interface remains fully adhered during a brief lip-closure rehearsal and that lead strain relief prevents tugging at the pad interface (see Figure 1G for representative placement).
5. Affix the pressure pad at the midline of the upper lip.
   1. Position the pressure-coupling pad so that its center aligns with the philtrum midline and the pad surface fully contacts the lip without spanning onto the cutaneous skin. Secure the pad using hypoallergenic surgical tape applied to the device margins, avoiding tape overlap across the sensing area.
   2. Apply approximately 1-2 N fingertip pressure for 5 s to seat the pad and eliminate micro-gaps, then visually confirm full contact (no visible blanching and no tape "bridging" across the pad). If a compliant diaphragm is used, ensure it remains centered and unoccluded after fixation (Figure 1G).
6. Insert the intraoral pressure catheter and stabilize the line.
   1. Insert the catheter centrally between the closed lips to a depth of 10-15 mm, ensuring the tubing does not contact the teeth edges or fold sharply at the lip margin. Confirm participant comfort and unobstructed breathing.
   2. Zero the pressure transducer at atmospheric pressure immediately before recording and re-check the baseline after fixation.
   3. Secure the catheter line to the cheek with tape and route it posteriorly to minimize motion transfer during tasks; ensure the line is not under tension and does not pull on the lip during cueing (Figure 1G).
7. Allow 2-3 min for stabilization. Record at least 30 s of baseline.
8. Collect participant-reported usability and tolerability outcomes (performed).
   1. After completing the full task battery (section 6), ask the participant to rate usability using a 0-10 numeric rating scale (0 = worst/most difficult, 10 = best/easiest) for the following items: (i) overall comfort of the PI/LIG lip sensor, (ii) comfort of the intraoral pressure interface/catheter, (iii) ease of completing the standardized tasks while wearing the system, and (iv) willingness to repeat the procedure in a future session.
   2. Record ratings on a standardized one-page form and document whether any discomfort required pausing or terminating the session (yes/no) and the primary reason (free text).
9. Document operator-reported setup time (performed).
   1. Start a stopwatch when skin preparation begins (step 5.3). Stop timing when stable baselines are obtained on all channels (end of step 5.7).
   2. Record setup time (min) for each participant and operator. If re-placement is required, include the additional time and note the reason.
10. Report usability items and summaries.
    1. Provide the exact usability item wording and anchors in Supplementary Table 3.
    2. Summarize participant-reported usability outcomes as median (IQR) for each item overall and by sex group in Supplementary Table 4. Summarize setup time using the same statistics and timing definition in Figure 6 or an equivalent table.
       NOTE: If any session is terminated due to discomfort, record the task at termination, the affected interface (lip sensor vs intraoral catheter), and whether any adverse event occurred. Include these events in the safety monitoring summary in the results.

6. Standardizing tasks and acquiring data

1. Provide standardized verbal cues paced by a 60 bpm metronome. Demonstrate each task once.
2. Instruct the participant to complete three tasks while maintaining consistent breathing and jaw posture.
   1. Instruct the participant to close the lips firmly without jaw clenching (lip closure).
   2. Instruct the participant to generate positive pressure through pursed lips (blowing).
   3. Instruct the participant to generate negative pressure through a straw-like interface (sucking).
3. Record five trials per task using a 3 s activation and 10 s rest paradigm. Randomize task order across participants using a Latin-square schedule.
4. Acquire all channels synchronously. Sample EMG at ≥1 kHz with ≥16-bit resolution. Sample pressure at ≥100 Hz. Apply appropriate anti-aliasing. If hardware filters are unavailable, apply matched digital low-pass filters below the Nyquist frequency. Annotate artifacts (speech, swallowing, coughing) during acquisition.
5. Prespecify analysis endpoints for correlation and agreement outcomes and prepare synchronized task traces to verify timing and channel alignment.
   NOTE: Summarize correlation/agreement outcomes in Figure 2 and provide representative synchronized task traces in Figure 3.

7. Processing signals and enforcing quality control

1. Filter EMG using a zero-phase 4th-order Butterworth band-pass filter (20-450 Hz). Apply a notch filter at 50 or 60 Hz according to local mains frequency. Rectify the signal and compute the linear envelope using a zero-phase 4th-order low-pass filter at 8-10 Hz. Document the chosen cutoff.
2. Low-pass filter pressure signals at 10-20 Hz using a zero-phase 4th-order filter. Convert voltages to kPa using device-specific calibration coefficients from step 4.2.
3. Align EMG envelopes with LP and IP using cue markers. Verify that peak timing differences are within ±200 ms. If misalignment exceeds tolerance, realign using cross-correlation and flag the trial.
4. Reject trials that meet any of the following criteria within the 3 s activation window: (i) dropout or saturation totaling > 0.6 s, (ii) baseline drift exceeding 3 SD of baseline RMS over 10 s, or (iii) motion-artifact bursts with envelope spikes > 5 SD of baseline during rest. Retain at least three valid trials per task and participant.
5. Summarize signal-processing settings and quality-control thresholds in Table 3.

8. Quantifying metrics and analyzing statistics

1. Compute within-participant Pearson correlations between PI/LIG-derived EMG and conventional EMG using trial-wise activation amplitudes defined as EMG RMS over the central 2 s of the 3 s activation window. Report r with 95% confidence intervals using Fisher's z transformation.
2. Compute correlations between LP and IP per task using the same analysis windows.
3. Assess agreement between PI/LIG-derived EMG and conventional EMG amplitudes using Bland-Altman analysis. Define bias as the mean paired difference, and limits of agreement as bias ± 1.96 SD of differences. If proportional bias is detected (p < 0.05 for regression of differences on means), repeat analysis on log-transformed amplitudes and back-transform limits.
4. If repeated blocks are available, estimate test-retest reliability using ICC(2,1) (two-way random-effects, absolute-agreement, single-measure) for EMG amplitude and peak pressure. Report ICC with 95% confidence intervals.
   NOTE: If repeated blocks are not available, omit ICC and state this explicitly in Results.
5. Prepare load-force time-course plots to visualize task dynamics and sex-group comparisons, and summarize these time-domain profiles in Figure 4.
6. Calculate signal-to-noise ratio in decibels: SNR_dB = 20·log10(RMS_active/RMS_baseline), where RMS_active is computed over the central 2 s of activation and RMS_baseline over the 1 s pre-cue rest. Summarize SNR distributions and include one illustrative noisy/failed example to demonstrate exclusion criteria in Figure 5.
7. Compare women and men on per-participant summaries (e.g., peak lip pressure, EMG RMS, and SNR). Test normality using Shapiro-Wilk. Use Welch's t-test for normally distributed data or Mann-Whitney U otherwise. Set two-sided α = 0.05. Report exact p-values and apply Holm-Bonferroni correction across three taskwise comparisons. Prepare setup-time comparisons using the same timing definitions across operators and summarize them in Figure 6.

9. Troubleshooting common issues

1. To address low EMG SNR, re-prep and fully dry the skin, re-seat electrodes at 11 ± 1 mm spacing, confirm impedance <10 kΩ, optimize cable shielding, and verify filter settings before repeating a single trial.
2. To correct pressure under-response, re-press the pad to ensure full contact (1-2 N for 5 s), remove tape wrinkles bridging the pad, and repeat calibration to meet step 4.2 acceptance criteria.
3. To resolve intraoral pressure drift, purge bubbles, re-seat the catheter to 10-15 mm depth, and re-zero the transducer before each block.
4. To reduce motion artifacts, rehearse cues, increase inter-trial rest to 15 s when needed, and flag contaminated epochs for exclusion.
5. Use the standardized troubleshooting matrix in Table 4 to document failure modes, corrective actions, and verification checks.

10. Safety, hygiene, and disposal

1. Use single-use intraoral interfaces and dispose of them as biohazard waste according to institutional policy.
2. Disinfect reusable holders and leads between participants. Document disinfectant and dwell time.
3. Monitor for skin irritation or discomfort. Terminate the session immediately if adverse events occur and record the event for IRB reporting.

Results

Device overview and calibration
The device architecture, placement, and bench calibration workflow are summarized in Figure 1. The module integrates two co-located laser-induced graphene (LIG) electrodes on a flexible polyimide (PI) substrate for orbicularis oris EMG (OOM-EMG) and a central pressure-coupling pad positioned on the upper-lip surface, together with a separate intraoral line for intraoral pressure (IP). Representative images of the fabricated device after la...

Discussion

This article reports an end-to-end protocol for synchronized monitoring of orbicularis oris electromyography (OOM-EMG), lip-closing pressure (LP), and intraoral pressure (IP) using a flexible polyimide/laser-induced graphene (PI/LIG) composite sensor coupled to a standardized acquisition and processing pipeline. Reproducibility in this workflow hinges on a small number of critical steps that determine whether recordings remain comparable across operators and sessions. First, fabrication must satisfy the prespecified elec...

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Alcohol prep pads	Dynarex	1113	70% isopropyl prep pads; Skin cleaning before electrode placement
BNC terminal block	National Instruments	BNC-2110	Use with NI shielded cable for DAQ connectivity; Breakout/connection for analog inputs
CO2 laser engraving/cutting system	Universal Laser Systems	VLS 3.50 (CO2)	Any CO2 laser system acceptable if Table 1 acceptance criteria are met; record laser model/settings used; LIG patterning on PI (10.6 μm class)
Conductive epoxy (silver)	MG Chemicals	8331	Cure conditions should match the implemented workflow; Lead attachment to LIG pads (optional alternative to solder)
Data acquisition device	National Instruments	USB-6343	Any DAQ meeting sampling/resolution requirements is acceptable; record the exact device used; Synchronous multi-channel recording (EMG ≥1 kHz; pressure ≥100 Hz)
Deionized water	Fisher Scientific	Laboratory grade DI water	Equivalent laboratory DI water acceptable; Post-pattern rinse
Desiccator	Kartell	554 (vacuum desiccator, 250 mm)	Any sealed desiccator + desiccant acceptable; record storage RH and duration; Dry storage (RH ≤30%) for finished devices
EMG disposable surface electrodes	Ambu	BlueSensor N (N-00-S/25)	Equivalent pre-gelled Ag/AgCl EMG electrodes acceptable; Reference EMG on orbicularis oris
Four-point probe system	Ossila	Four-Point Probe System (T2001A5)	Any four-point probe system acceptable; record probe spacing/measurement points; Sheet resistance (Ω/) screening
Hypoallergenic surgical tape	Solventum	Micropore Surgical Tape 1530 (Product ID 7100273771)	Equivalent hypoallergenic surgical tape acceptable; Fix pressure pad at upper lip midline
Isopropyl alcohol (IPA), ≥99%	Merck (Sigma-Aldrich)	190764-500ML	Record supplier and lot number in lab log; Post-pattern rinse; general cleaning
Manometry/pressure catheter line	KRUUSE	Feeding tube, 8 Fr (230811)	Any catheter/tube meeting OD and safety requirements acceptable; record exact model used; Intraoral pressure (IP) line, OD ~2–3 mm
Metronome	Korg	MA-2	App-based metronome acceptable if documented (device + app name/version); Cue pacing (60 bpm)
Micrometer	Mitutoyo	293-340-30 (0–25 mm)	Any micrometer meeting resolution needs acceptable; Verify PI thickness (±1 μm tolerance)
Polyimide film (25 μm)	Merck (Sigma-Aldrich)	GF59627009	0.025 mm thickness; record lot number; keep thickness consistent within each batch; Substrate for PI/LIG device
Polyimide film (50 μm)	Goodfellow	1000106786	0.05 mm thickness; record lot number; do not mix calibration coefficients across devices; Substrate for PI/LIG device
Pressure transducer (USB output)	Omega Engineering	PX409-USBH series	Select range to cover ±20 kPa requirement; record exact range/model used; IP measurement (resolution ≤0.1 kPa recommended)
Shielded cable (68-pin)	National Instruments	SHC68-68-EPM	Use with NI BNC-2110 for shielded connections; DAQ connectivity (USB-6343 to terminal block)
Silicone elastomer film (diaphragm)	Goodfellow	Silicone elastomer film 0.125 mm (Ref 1000181130)	Optional; apply consistently if used and record thickness/fixation method; Optional compliant diaphragm (100–200 μm)
Silicone elastomer kit (PDMS)	Dow	SYLGARD 184 kit	Use consistently within a batch; record mixing ratio and curing conditions; Encapsulation (target dry thickness 10–30 μm)
Solder wire	Kester	24-6337-0027 (Sn63/Pb37, rosin core, 0.031 in)	If lead-free solder is used, record alloy and flux type; Lead attachment (if soldering is used)
Software (signal processing)	Python Software Foundation	Python 3.x + NumPy/SciPy/Matplotlib	Document exact versions of Python and packages in Methods or Supplementary Methods; Filtering, synchronization, statistics, plotting