{ "title": "S-HASEL Actuator Evidence: 20 µm Films, 1.2 mL Fill, Zero MRI Tests", "rciNumber": "RCI 030", "version": "0.1.0", "schemaVersion": 1, "released": "2026-08-10", "canonical": "https://robotcomponentindex.com/research/s-hasel-actuator-evidence-audit/", "scope": "Public-evidence and reproducibility audit of Research Square preprint rs-10623292 v1. RCI resolved the official item record, verified its item-level CC BY 4.0 license, downloaded and hashed the only public manuscript file, extracted its text, rendered and visually checked all 16 covered-PDF pages, and separated tested single-actuator evidence from the proposed three-stack biopsy robot. RCI did not fabricate an actuator, digitize plots, run the test benches, reproduce the self-sensing model, test needle puncture, or test MRI compatibility.", "source": { "title": "Toward Soft-Robotic Image-Guided Tumor Puncture: Development and Control of a HASEL Actuator for Integration into a Novel Soft Robotic Concept", "authors": [ "Fabian Sadi", "Urs Florian Herrmann", "Marius Siegfarth" ], "affiliation": "Mannheim Institute for Intelligent Systems in Medicine (MIISM), Heidelberg University Medical Faculty Mannheim", "doi": "10.21203/rs.3.rs-10623292/v1", "version": "v1", "posted": "2026-08-10", "recordUrl": "https://www.researchsquare.com/article/rs-10623292/v1", "pdfUrl": "https://www.researchsquare.com/article/rs-10623292/v1.pdf", "publicationType": "Research Square preprint; not peer reviewed by a journal", "licenseName": "Creative Commons Attribution 4.0 International", "licenseShortName": "CC BY 4.0", "licenseUrl": "https://creativecommons.org/licenses/by/4.0/", "verifiedDate": "2026-08-10" }, "independentAudit": { "method": "RCI checked the official Research Square v1 item and covered PDF, verified the license statement on both surfaces, recorded the PDF size and SHA-256, extracted the complete text, rendered all pages, visually inspected pages 1 through 16, and audited hardware identity, test conditions, result semantics, artifact availability and application-stage evidence. RCI did not copy the PDF or figures into the public release and did not perform a physical or software reproduction.", "officialPublicFileCount": 1, "pdfPageCount": 16, "pdfPagesVisuallyChecked": [ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16 ], "pdfBytes": 2514822, "pdfSha256": "cc9da81a1e63410140d4e0451b4a5c6a089cb91f6473d5cdb47e6791e4a29c94", "supplementaryFileCount": 0, "publicRawDataFileCount": 0, "publicCodeFileCount": 0, "publicCadFileCount": 0, "publicBomFileCount": 0, "publicSchematicFileCount": 0, "authorReportedNrmseCount": 4, "nrmseRecomputedByRci": false, "plotDataDigitizedByRci": false, "physicalTestPerformedByRci": false, "sourceFiguresRedistributedByRci": false, "independentReplicationCount": 0 }, "observations": [ { "id": "RCI030-O01", "field": "proposed_robot_actuator_stack_count", "value": "3", "unit": "stacks", "sourceLocation": "Section 4.1; Figure 3", "evidenceRole": "author-proposed system architecture", "rciBoundary": "The paper presents the three-stack arrangement as a robot concept; it does not report an assembled or tested three-stack robot." }, { "id": "RCI030-O02", "field": "proposed_stack_angular_spacing", "value": "120", "unit": "degrees", "sourceLocation": "Section 4.1", "evidenceRole": "author-proposed system architecture", "rciBoundary": "Angular spacing is a design statement, not a measured alignment or kinematic calibration result." }, { "id": "RCI030-O03", "field": "proposed_needle_positioning_degrees_of_freedom", "value": "2", "unit": "DOF", "sourceLocation": "Section 4.1", "evidenceRole": "author-proposed system architecture", "rciBoundary": "No integrated two-DOF trajectory, accuracy, repeatability or workspace result is reported." }, { "id": "RCI030-O04", "field": "actuator_drawing_outer_height", "value": "53", "unit": "mm", "sourceLocation": "Figure 3 right", "evidenceRole": "author-figure dimension", "rciBoundary": "A two-dimensional figure dimension; no tolerance, thickness stack-up or released CAD is provided." }, { "id": "RCI030-O05", "field": "actuator_drawing_outer_width", "value": "36", "unit": "mm", "sourceLocation": "Figure 3 right", "evidenceRole": "author-figure dimension", "rciBoundary": "A two-dimensional figure dimension; it does not establish the complete manufactured geometry." }, { "id": "RCI030-O06", "field": "central_cutout_shift", "value": "4", "unit": "mm", "sourceLocation": "Section 4.1; Figure 3 right", "evidenceRole": "author-reported design detail", "rciBoundary": "The shift is reported as an air-breakdown mitigation choice; dielectric-breakdown testing for the geometry is not published." }, { "id": "RCI030-O07", "field": "high_voltage_tab_offset", "value": "50", "unit": "degrees", "sourceLocation": "Section 4.1", "evidenceRole": "author-reported design detail", "rciBoundary": "No tab tolerance, conductor width, creepage calculation or released drawing accompanies the angle." }, { "id": "RCI030-O08", "field": "tested_film_materials", "value": "BOPP; BoPET heat-seal film sold as Mylar 850 (DuPont)", "unit": null, "sourceLocation": "Section 4.3", "evidenceRole": "author-reported fabrication condition", "rciBoundary": "Mylar 850 is named; the BOPP grade, supplier, batch and surface treatment are not disclosed." }, { "id": "RCI030-O09", "field": "film_thickness", "value": "20", "unit": "µm", "sourceLocation": "Section 4.3", "evidenceRole": "author-reported fabrication condition", "rciBoundary": "Nominal film thickness is reported without tolerance or independently measured thickness distribution." }, { "id": "RCI030-O10", "field": "dielectric_fluid", "value": "Low-viscosity silicone oil; 5 cSt; Carl Roth", "unit": null, "sourceLocation": "Section 4.3", "evidenceRole": "author-reported fabrication condition", "rciBoundary": "The exact catalog number, lot, temperature and measured fluid properties are not provided." }, { "id": "RCI030-O11", "field": "tested_fill_volumes", "value": "1.0; 1.2; 1.4", "unit": "mL", "sourceLocation": "Section 5; Figure 8", "evidenceRole": "author-reported test matrix", "rciBoundary": "Only these three fill levels within the reported geometry were compared; this is not a global optimization over HASEL designs." }, { "id": "RCI030-O12", "field": "selected_configuration", "value": "BOPP with 1.2 mL fill", "unit": null, "sourceLocation": "Abstract; Section 5; Conclusion", "evidenceRole": "author-reported within-study selection", "rciBoundary": "“Selected” and “optimal” apply to the two films, three fill levels and reported bench protocol, not to every material, volume or application." }, { "id": "RCI030-O13", "field": "material_test_replication_statement", "value": "Three S-HASEL actuators per material; three independent trials per fill volume", "unit": null, "sourceLocation": "Section 5", "evidenceRole": "author-reported sample and trial statement", "rciBoundary": "The text does not fully resolve actuator reuse across fill conditions, trial independence, batch allocation or error-bar definition." }, { "id": "RCI030-O14", "field": "figure_8_constant_force_levels", "value": "0.2; 0.4; 0.6; 0.8", "unit": "N", "sourceLocation": "Figure 8 legends", "evidenceRole": "author-figure test condition", "rciBoundary": "These are plotted constant-load conditions, not maximum force, blocked force or an independently calibrated force envelope." }, { "id": "RCI030-O15", "field": "force_test_load_cell", "value": "KM40e 100N/010; ME-Meßsysteme", "unit": null, "sourceLocation": "Section 4.2", "evidenceRole": "author-reported test-bench identity", "rciBoundary": "No calibration certificate, calibration date, uncertainty or complete signal chain is published." }, { "id": "RCI030-O16", "field": "force_test_linear_stage", "value": "XR50P; Thorlabs", "unit": null, "sourceLocation": "Section 4.2", "evidenceRole": "author-reported test-bench identity", "rciBoundary": "The stepper motor, controller, stage settings, alignment and fixture compliance are not completely specified." }, { "id": "RCI030-O17", "field": "self_sensing_ground_truth_sensor", "value": "HG-C1100 micro-laser distance sensor; Panasonic", "unit": null, "sourceLocation": "Section 4.2; Figure 5", "evidenceRole": "author-reported ground-truth instrument", "rciBoundary": "No calibration, target reflectivity error, alignment error, sampling synchronization or uncertainty budget is reported." }, { "id": "RCI030-O18", "field": "self_sensing_excitation", "value": "DG 2021 A function generator; 20 V sinusoidal excitation", "unit": null, "sourceLocation": "Section 4.2", "evidenceRole": "author-reported sensing condition", "rciBoundary": "The excitation frequency and complete component values for the sensing circuit are not stated in this paper." }, { "id": "RCI030-O19", "field": "self_sensing_data_acquisition", "value": "PXI-6255; 200 kHz sampling", "unit": null, "sourceLocation": "Section 4.2", "evidenceRole": "author-reported acquisition condition", "rciBoundary": "The sample rate is not a demonstrated actuator bandwidth, control-loop rate or independent accuracy result." }, { "id": "RCI030-O20", "field": "dc_training_sweep", "value": "0–7 kV in 200 V steps", "unit": null, "sourceLocation": "Section 4.2", "evidenceRole": "author-reported training condition", "rciBoundary": "Dwell time, ramp timing, cycle history, temperature and raw samples are not published." }, { "id": "RCI030-O21", "field": "self_sensing_model", "value": "Second-degree polynomial (Poly 2) fit from RMS voltage to displacement", "unit": null, "sourceLocation": "Section 4.2", "evidenceRole": "author-reported model method", "rciBoundary": "Coefficients, training data, model files, preprocessing and code are not publicly released." }, { "id": "RCI030-O22", "field": "pwm_logic_components", "value": "LTC6992-1 timer; SN74LVC2G86 XOR gate; optocoupler half-bridge", "unit": null, "sourceLocation": "Section 4.2; Figure 6", "evidenceRole": "author-reported circuit architecture", "rciBoundary": "The optocoupler identities, passive values, schematic, PCB, firmware and safety design are not released." }, { "id": "RCI030-O23", "field": "pwm_test_condition", "value": "150 Hz PWM; 7 kV fixed high voltage; 0–100% duty in 0.25% steps", "unit": null, "sourceLocation": "Section 4.2", "evidenceRole": "author-reported drive condition", "rciBoundary": "This drive condition is not evidence of 150 Hz mechanical bandwidth, three-stack control or MRI-safe operation." }, { "id": "RCI030-O24", "field": "high_voltage_generator", "value": "20HVA24-P2 UltraVolt; controllable by 10 V analog input", "unit": null, "sourceLocation": "Section 4.2", "evidenceRole": "author-reported power-supply identity", "rciBoundary": "The paper does not publish output-current measurements, energy per cycle, efficiency, fault response or MRI compatibility for the supply." }, { "id": "RCI030-O25", "field": "graphite_and_first_gold_nrmse", "value": "0.1639 graphite; 0.0429 gold", "unit": "NRMSE", "sourceLocation": "Section 4.3; Figure 7", "evidenceRole": "author-reported validation results", "rciBoundary": "The normalization definition, raw traces, model coefficients and repeated-sample statistics are not released; RCI did not recompute either value." }, { "id": "RCI030-O26", "field": "gold_sputtering_condition", "value": "250 nm Au; 0.04 mbar argon; 25 mA; SCD 004 Balzers Union", "unit": null, "sourceLocation": "Section 4.3", "evidenceRole": "author-reported fabrication condition", "rciBoundary": "Deposition time, thickness-uniformity measurement, adhesion test, mask geometry and batch yield are not reported." }, { "id": "RCI030-O27", "field": "final_outer_coating", "value": "Thin dip-coated silicone layer; Ecoflex 0030; Smooth-On", "unit": null, "sourceLocation": "Section 4.3", "evidenceRole": "author-reported fabrication condition", "rciBoundary": "Thickness, cure schedule, coverage, dielectric test and effect on mechanics are not quantified." }, { "id": "RCI030-O28", "field": "final_self_sensing_validation_protocol", "value": "Three cycles; DC ramp 0–6 kV; PWM duty 0–100%", "unit": null, "sourceLocation": "Section 5; Figure 9", "evidenceRole": "author-reported validation protocol", "rciBoundary": "The three-cycle test is short-duration author evidence; raw time series and actuator-to-actuator replication are not public." }, { "id": "RCI030-O29", "field": "final_dc_and_pwm_nrmse", "value": "0.0126 DC; 0.0078 PWM", "unit": "NRMSE", "sourceLocation": "Abstract; Section 5; Figure 9", "evidenceRole": "author-reported validation results", "rciBoundary": "NRMSE is not absolute positioning accuracy, closed-loop error, MRI performance or clinical targeting accuracy; RCI did not recompute it." }, { "id": "RCI030-O30", "field": "dc_pwm_displacement_and_relaxation_comparison", "value": "DC displacement 0.18 mm larger; residual 0.043 mm at 0 kV versus 0.1 mm at 0% PWM; 9 s initial PWM plateau", "unit": null, "sourceLocation": "Section 5; Figure 9", "evidenceRole": "author-reported comparison", "rciBoundary": "These values describe the reported validation sequence and must not be generalized to all HASEL designs, loads or controllers." } ], "disclosureAudit": [ { "id": "RCI030-D01", "field": "item_identity_version_and_license", "status": "disclosed", "publicEvidence": "The official Research Square record and covered PDF identify DOI v1, posted date, authors and CC BY 4.0.", "reproductionImpact": "The exact source version and item-level reuse terms can be cited and revisited." }, { "id": "RCI030-D02", "field": "peer_review_status", "status": "disclosed-preprint", "publicEvidence": "Research Square states that the work is a preprint and has not been peer reviewed by a journal.", "reproductionImpact": "Every result remains preliminary author evidence." }, { "id": "RCI030-D03", "field": "actuator_geometry", "status": "partial", "publicEvidence": "Figure 3 gives a 53 mm by 36 mm outline plus selected offsets and electrode regions.", "reproductionImpact": "No complete dimensioned drawing, tolerance stack, seal geometry or CAD is released." }, { "id": "RCI030-D04", "field": "materials_and_fluids", "status": "partial", "publicEvidence": "Film families, nominal thickness, Mylar 850 identity, silicone-oil viscosity/vendor and Ecoflex 0030 are stated.", "reproductionImpact": "The BOPP grade, catalog numbers, lots and measured material properties remain unknown." }, { "id": "RCI030-D05", "field": "heat_seal_fabrication_process", "status": "not-disclosed", "publicEvidence": "The actuator is described as heat sealed and prior work is cited, but this paper gives no complete sealing recipe.", "reproductionImpact": "Temperature, pressure, dwell, tooling, cut sequence and yield cannot be reproduced from v1." }, { "id": "RCI030-D06", "field": "electrode_fabrication", "status": "partial", "publicEvidence": "Graphite stencil coating and gold sputtering conditions are described; the gold layer is reported as 250 nm.", "reproductionImpact": "Masks, deposition time, resistance maps, adhesion, alignment tolerance and yield are absent." }, { "id": "RCI030-D07", "field": "material_test_protocol", "status": "partial", "publicEvidence": "Two films, three fill volumes, four plotted loads and voltage sweeps are visible or stated.", "reproductionImpact": "Dwell, ramp rate, order, preconditioning, ambient state and rejection rules are not fully defined." }, { "id": "RCI030-D08", "field": "sample_allocation_and_statistics", "status": "partial", "publicEvidence": "The paper says three actuators per material and three independent trials per fill volume, with mean values and error bars.", "reproductionImpact": "Reuse across fill levels, batch assignment, independence and the error-bar statistic are not fully specified." }, { "id": "RCI030-D09", "field": "instrument_calibration_and_uncertainty", "status": "not-disclosed", "publicEvidence": "Exact load-cell and laser models are named, but no calibration record or uncertainty budget is provided.", "reproductionImpact": "Force, stroke and NRMSE traceability cannot be independently quantified." }, { "id": "RCI030-D10", "field": "material_test_raw_data", "status": "not-released", "publicEvidence": "Figure 8 shows means and error bars; the official item exposes one PDF and no data file.", "reproductionImpact": "Plot values, variability, exclusions and alternative analyses cannot be independently checked." }, { "id": "RCI030-D11", "field": "self_sensing_circuit", "status": "partial", "publicEvidence": "The Voltage Method, omitted 1:2 stage, instruments and a high-level block diagram are described.", "reproductionImpact": "No complete schematic, passive values, excitation frequency, PCB or noise characterization is released." }, { "id": "RCI030-D12", "field": "model_training_artifacts", "status": "not-released", "publicEvidence": "A local second-degree polynomial training workflow is described.", "reproductionImpact": "Training traces, coefficients, model files and MATLAB code cannot be rerun or version matched." }, { "id": "RCI030-D13", "field": "nrmse_definition_and_recomputation", "status": "partial", "publicEvidence": "Four NRMSE values are printed, but the normalization denominator and calculation code are not supplied.", "reproductionImpact": "The metrics cannot be independently recomputed or safely compared with differently normalized studies." }, { "id": "RCI030-D14", "field": "timing_filtering_and_latency", "status": "partial", "publicEvidence": "DAQ sampling is 200 kHz and PWM is 150 Hz; a 9 s PWM plateau is reported.", "reproductionImpact": "Clocking, filtering, RMS window, latency and mechanical bandwidth remain unresolved." }, { "id": "RCI030-D15", "field": "maximum_force_stress_and_work_density", "status": "not-reported", "publicEvidence": "Figure 8 uses constant loads up to 0.8 N, but no blocked-force, maximum-force, stress or work-density result is reported for S-HASEL.", "reproductionImpact": "The actuator cannot be compared as a force-rated component from this paper alone." }, { "id": "RCI030-D16", "field": "dynamic_response_and_bandwidth", "status": "not-reported", "publicEvidence": "The paper plots slow validation cycles but gives no step response, frequency response or bandwidth.", "reproductionImpact": "The 150 Hz electrical PWM rate must not be treated as actuator bandwidth." }, { "id": "RCI030-D17", "field": "power_energy_and_efficiency", "status": "not-reported", "publicEvidence": "The high-voltage source is identified, but electrical current, energy per stroke and efficiency are absent.", "reproductionImpact": "Power-system sizing and energy comparison remain unsupported." }, { "id": "RCI030-D18", "field": "durability_breakdown_and_cycle_life", "status": "not-reported", "publicEvidence": "Three final validation cycles are reported; no endurance, failure distribution, leakage-current or breakdown-voltage study is published.", "reproductionImpact": "Reliability, maintenance interval and safe operating life cannot be inferred." }, { "id": "RCI030-D19", "field": "closed_loop_position_control", "status": "future-work", "publicEvidence": "The conclusion says the self-sensing approach will serve as the basis for a position-control system.", "reproductionImpact": "The paper validates estimation only; it does not demonstrate closed-loop positioning." }, { "id": "RCI030-D20", "field": "integrated_three_stack_robot", "status": "concept-only", "publicEvidence": "A patient-mounted three-stack robot is shown as a concept and described as the objective of future development.", "reproductionImpact": "No assembled robot, workspace, kinematics, trajectory or two-DOF accuracy result is published." }, { "id": "RCI030-D21", "field": "needle_puncture_and_tissue_test", "status": "not-tested", "publicEvidence": "The paper motivates needle biopsy but reports actuator bench tests only.", "reproductionImpact": "No needle force, targeting, phantom, tissue, animal or human result supports the application title." }, { "id": "RCI030-D22", "field": "mri_compatibility_test", "status": "future-work", "publicEvidence": "The conclusion states that the complete system will subsequently be tested and adapted to MRI conditions.", "reproductionImpact": "Zero MRI-environment tests, image-artifact measurements or MR-safety results are reported." }, { "id": "RCI030-D23", "field": "code_cad_bom_and_schematic_release", "status": "not-released", "publicEvidence": "The official item exposes one manuscript PDF and no supplementary data, code, CAD, BOM or schematic file.", "reproductionImpact": "The actuator, sensing electronics, PWM driver and test workflow are not build-ready from the public package." }, { "id": "RCI030-D24", "field": "independent_replication", "status": "not-found", "publicEvidence": "No independent reproduction of this S-HASEL geometry and result set is linked by the v1 record or manuscript.", "reproductionImpact": "The reported behavior remains author evidence from one research group." }, { "id": "RCI030-D25", "field": "clinical_safety_sterility_and_regulatory_evidence", "status": "not-applicable-at-this-stage", "publicEvidence": "The item is a preclinical actuator-development preprint with no human or vertebrate-subject study declared.", "reproductionImpact": "No clinical effectiveness, patient safety, sterilization, biocompatibility or regulatory claim can be made." } ], "applicationStageBoundary": [ { "stage": "Single S-HASEL actuator fabricated", "status": "author-tested", "evidence": "Bench photographs, fabrication description and material comparisons are present." }, { "stage": "Single-actuator displacement self-sensing", "status": "author-tested", "evidence": "Laser-referenced DC and PWM validation cycles and NRMSE values are reported." }, { "stage": "Closed-loop position control", "status": "not-tested", "evidence": "Explicitly described as future work." }, { "stage": "Integrated three-stack, two-DOF robot", "status": "concept-only", "evidence": "Only a proposed architecture and concept rendering are published." }, { "stage": "Needle insertion or tissue puncture", "status": "not-tested", "evidence": "No phantom, ex vivo, in vivo or human puncture test is reported." }, { "stage": "MRI environment and image-artifact validation", "status": "not-tested", "evidence": "The authors state this will be tested and adapted subsequently." }, { "stage": "Clinical use", "status": "not-supported", "evidence": "The preprint cover warns against using preliminary reports to inform clinical practice." } ], "resultBoundary": { "assessment": "single-actuator-bench-evidence-only", "selectedConfiguration": "BOPP film, 20 µm nominal thickness, 1.2 mL silicone-oil fill and sputtered gold electrodes within the reported study matrix", "reportedNrmse": { "graphiteFigure7": 0.1639, "goldFigure7": 0.0429, "goldDcFigure9": 0.0126, "goldPwmFigure9": 0.0078 }, "conclusion": "The public evidence supports that the authors fabricated and bench-tested individual S-HASEL actuators, selected BOPP with 1.2 mL fill within a bounded material matrix, and reported improved displacement-estimation NRMSE with gold electrodes. It does not establish a force rating, mechanical bandwidth, lifetime, closed-loop accuracy, integrated robot performance, needle-puncture capability, MRI compatibility or clinical usefulness." }, "rightsBoundary": { "sourceLicense": "The official Research Square v1 item and the first page of its covered PDF both state Creative Commons Attribution 4.0 International.", "rciTreatment": "RCI may quote and adapt the work with attribution under CC BY 4.0, but this v0.1.0 release publishes independently written facts, audit rows and analysis only. It links the official record and PDF and does not mirror the manuscript.", "figureTreatment": "No source figure is reproduced in this release. This avoids implying that every embedded third-party visual element has been separately cleared, while preserving direct links and source locations for verification." }, "limitations": [ "RCI audited the public Research Square v1 item and its only public PDF file; it did not inspect laboratory notebooks, private data, hardware or later versions.", "All performance values are author-reported. RCI did not digitize the plots or recompute the four NRMSE values.", "The absence counts for data, code, CAD, BOM, schematic and supplementary files are bounded to the official public item surfaces checked on 2026-08-10; private or later artifacts may exist.", "The selected 1.2 mL BOPP configuration is best only within the stated study matrix and protocol, not a universal HASEL optimum.", "The 200 kHz DAQ rate and 150 Hz PWM carrier are electrical/acquisition conditions, not measured mechanical or closed-loop bandwidths.", "No claim is made about needle-biopsy effectiveness, MRI safety, image artifacts, sterilization, biocompatibility, clinical safety or regulatory status." ], "suggestedCitation": "Robot Component Index. “S-HASEL Actuator Evidence: 20 µm Films, 1.2 mL Fill, Zero MRI Tests.” RCI 030, research dataset version 0.1.0, 2026-08-10. https://robotcomponentindex.com/research/s-hasel-actuator-evidence-audit/" }