Low Contact Force Research Articles

Influence of contact force on voltage mapping: A combined magnetic resonance imaging and electroanatomic mapping study in patients with tetralogy of Fallot

Voltage criteria for ventricular mapping have been obtained from small series of patients and prioritizing high specificity. The purpose of this study was to analyse the potential influence of contact force (CF) on voltage mapping and to define voltage cutoff values for right ventricular (RV) scar using the tetralogy of Fallot as a model of transmural RV scar and magnetic resonance imaging (MRI) as reference. Fourteen patients (age 32.6 ± 14.3 years; 5 female) with repaired tetralogy of Fallot underwent high-resolution cardiac MRI (1.25 × 1.25 × 2.5 mm). Scar, defined as pixels with intensity >50% maximum, was mapped over the RV geometry and merged within the CARTO system to RV endocardial voltage maps acquired using a 3.5-mm ablation catheter with CF technology (SmartTouch, Biosense Webster). In total, 2446 points were analyzed, 915 within scars and 1531 in healthy tissue according to MRI. CF correlated to unipolar (ρ= 0.186; P <.001) and bipolar voltage in healthy tissue (ρ=0.245; P <.001) and in scar tissue. Receiver operating characteristic curve analysis excluding points with very low CF (<5g) identified optimal voltage cutoffs of 5.19 mV for unipolar voltage and 1.76 mV for bipolar voltage, yielding sensitivity/specificity of 0.89/0.85 and 0.9/0.9, respectively. CF is an important factor to be taken into account for voltage mapping. If good CF is applied, unipolar and bipolar voltage cutoffs of 5.19 mV and 1.76 mV are optimal for identifying RV scar on endocardial mapping with the SmartTouch catheter. Data on the diagnostic accuracy of different voltage cutoff values are provided.

Contact force facilitates the achievement of an unexcitable ablation line during pulmonary vein isolation.

Contact force (CF) catheters provide catheter-tissue contact information to improve outcome of pulmonary vein isolation (PVI) in paroxysmal atrial fibrillation (PAF). We evaluated different target-CF values for achievement of the additional endpoint of an unexcitable ablation line. A total of 106 patients undergoing PVI were randomized into three groups (G) (G1: target-CF 15g, G2: target-CF 10g, G3: CF concealed from operator). The PVI encircling line was divided into predefined sections. Excitable tissue along the PVI-line identified by high output pacing (10V, 2ms) was targeted for further ablation. Mean average CF was 17.4 ± 4.7g (G1) vs. 12.3 ± 6.0g (G2) vs. 11.1 ± 6.5g (G 3) (p < 0.001). Primary unexcitable ablation lines were found in 38.6, 19.4 and 5.7% (G1, G2, G3 respectively; G1 vs. G2 p < 0.05, G1 vs. G3 p < 0.001, G2 vs. G3 ns). Additional radiofrequency (RF)-energy to achieve unexcitability was lowest in G1 (3.6 ± 3.1kJ vs. 8.6 ± 7.2kJ (G2) and 10.4 ± 6.7 (G3), p ≤ 0.001, G2 vs. G3 ns) with accordingly lowest additional RF applications in G1 (3.0 ± 2.6 vs. 7.0 ± 5.4 in G2 and 8.4 ± 4.0 in G3; G1 vs. G2 and G3, p < 0.001, G 2 vs. G 3ns). Sections along ablation lines with low initial CF were most likely to reveal excitability. Single procedure success was 81.9 vs. 73.5 vs. 71.4% (G 1, 2 and 3, p = 0.6) during 437 ± 254day follow-up. Higher tip-to-tissue CF during PVI facilitates the achievement of an unexcitable ablation line, requiring less additional RF-energy.

Recurrence after pulmonary vein isolation is associated with low contact force

Objectives. Recurrent arrhythmia after pulmonary vein isolation (PVI) by radiofrequency (RF) ablation in patients with atrial fibrillation (AFIB) remains a significant challenge. Using contact force (CF) sensing ablation catheters, we aimed to identify procedure related parameters associated with recurrence after de-novo PVI in patients with AFIB. Methods. Consecutive patients undergoing a de-novo PVI procedure (n = 120, 63% paroxysmal and 37% persistent AFIB) employing a force-sensing ablation catheter were included. A clinical control including electrocardiogram and 120 hour of Holter-recording at 12-months was performed in all patients. Recurrence was defined as any documented AFIB or atrial flutter more than 30 seconds on Holter-recording after an initial blanking period of three months. Results. Recurrence occurred in 44 patients (37%). Mean CF was lower in patients with recurrent arrhythmia (22.2 ± 9.5 vs. 28.8 ± 9.3 g, p < .001). In multi-variable analyses lower mean CF (OR 0.9 (95% CI 0.8–1.0), p = .03), and higher percentage of ablation time with a CF <10 grams (OR 1.1 (95% CI 1.0–1.1), p = .004) were both associated with recurrence in two distinct models. Dragging during ablation compared with point-by-point ablation technique was associated with recurrence in both models (OR 19.2 (95% CI 2.9–130.0), p = .002, and OR 21.7 (95% CI 2.7–176.2), p = .004). Conclusions. Low CF and dragging during ablation as compared with point-by-point ablation technique were associated with recurrent arrhythmia in patients with AFIB undergoing de-novo PVI by RF ablation.

In vivo hip joint loads and pedal forces during ergometer cycling

The rising prevalence of osteoarthritis and an increase in total hip replacements calls for attention to potential therapeutic activities. Cycling is considered as a low impact exercise for the hip joint and hence recommended. However, there are limited data about hip joint loading to support this claim. The aim of this study was to measure synchronously the in vivo hip joint loads and pedal forces during cycling. The in vivo hip joint loads were measured in 5 patients with instrumented hip implants. Data were collected at several combinations of power and cadence, at two saddle heights.Joint loads and pedal forces showed strong linear correlation with power. So the relationship between the external pedal forces and internal joint forces was shown. While cycling at different cadences the minimum joint loads were acquired at 60RPM. The lower saddle height configuration results in an approximately 15% increase compared to normal saddle height.The results offered new insights into the actual effects of cycling on the hip joint and can serve as useful tools while developing an optimum cycling regimen for individuals with coxarthrosis or following total hip arthroplasty. Due to the relatively low contact forces, cycling at a moderate power level of 90W at a normal saddle height is suitable for patients.

P878Comparison of esophageal complications following radiofrequency ablation for atrial fibrillation between low contact and high contact force:A prospective, randomized study

P878Comparison of esophageal complications following radiofrequency ablation for atrial fibrillation between low contact and high contact force:A prospective, randomized study

A novel ultrasonic surface machining tool utilizing elastic traveling waves

With the rapid development of modern industrial technology and high performance technology products, ultra-precision machining technology becomes increasingly important. However, joint clearance of kinematic pairs, lack of feeding accuracy and overlarge contact stress still limit the further improvement of ultra-precision machining technology. In this study, a novel surface machining method utilizing structural elastic waves was proposed, and a machining tool using the piezoelectric actuating principle was presented for verifying the proposed method. Two vibration modes with a phase shift of π/2 in both space and time domains are exited simultaneously in the elliptical motion of points on the structural surface. By means of adjusting driving signal parameters, such as frequency, voltage amplitude and phase shift, different machining performances could be achieved. The configuration and working vibration modes of the proposed machining tool were firstly calculated by the finite element method, and then the optimal working frequency of the machining tool prototype was determined by vibration characteristic experiments. At last, machining characteristic experiments were conducted to validate the proposed machining method. Experimental results showed that the minimum working contact force between the machining tool and workpiece was 1N, and the chipped depth of 1.93μm was achieved at the same contact force after machining for 5min. And at the conditions of the contact force of 6N, two driving voltages of 400Vpp with a phase shift of π/2, and machining time of 5min, the prototype could achieve to machine the workpiece most efficiently and the roughness of the machined workpiece surface could be reached approximating 0.20μm. In conclusion, this proposed machining method could achieve a good quality machined surface with low residual stress and little damage by applying low contact force. Furthermore, it also had the advantage of no joint clearance error due to no kinematic pair in the structure, which improves the machining precision.

Hysteretic behavior of contact force response in triboelectric nanogenerator

The hysteretic behavior of contact force response in a triboelectric nanogenerator is analyzed as the output performance in response to the applied contact force is found to be dependent on previous contact force history. The counterclockwise hysteresis curve of the contact force versus output power originates from the asymmetric time constant between triboelectric charging and natural discharging, because the charges due to contact electrification do not immediately disappear but gradually decay over a period of hours. Therefore, a low contact force followed immediately after a high contact force results in enhanced output performance but not the reverse order. However, if the intermission time becomes too long, the benefit due to charge balance gets degraded. The experimental results on sweep range and discharging time dependencies agree well with theoretical expectations.

First Metatarsophalangeal Contact Properties Following Proximal Opening Wedge and Scarf Osteotomies for Hallux Valgus Correction: A Biomechanical Study.

Proximal opening wedge osteotomy (POWO) is an established procedure for moderate to severe hallux valgus. A common concern of this procedure is that it results in lengthening of the first metatarsal, which could cause increased intra-articular pressure of the first metatarsophalangeal joint (MTP) and may ultimately lead to arthritis because of these altered mechanics. The purpose of this study was to use a cadaveric model to compare intra-articular pressures and articulating contact properties of the MTP joint following either scarf osteotomy or POWO. Fresh-frozen cadaveric below-knee specimens with pre-existing hallux valgus (n = 12) and specimens without hallux valgus (n = 6, control group) were used. The hallux valgus specimens were stratified into 2 groups (n = 6 each): POWO or scarf osteotomy. The groups were matched based on the degree of deformity. Peak intra-articular pressure, force, and area were measured in all normal, preoperative, and postoperative specimens with a simulated weightbearing model. These measurements were made with a pressure transducer placed within the first MTP joint. Postoperatively POWO group had slightly higher contact forces and pressures compared to the scarf group and lower contact forces and pressures than those of the normal group but were not statistically significant ( P > .05). Normal specimens had higher intra-articular force, pressure, and area than postoperative specimens but the difference was not found to be significant. First metatarsal lengthening was found in both the scarf and POWO specimens; however, neither increase was found to be significant ( P > .05). The results from this study show that after operative correction, contact properties of the fist MTP joint among normal, POWO, and scarf osteotomy groups revealed no significant differences. First MTP joints in those with hallux valgus had significantly lower contact force and pressure compared to those without hallux valgus. With little long-term outcomes of proximal opening wedge osteotomy, this study will help predict the possibility of future MTP joint arthritis.

Can you feel what I feel?

Robotics By combining tactile sensations of hardness, ductility, shape, and surface texture, and then comparing these with our previous experiences, it is possible to safely grasp a random object placed in our hands without needing to see it. However, most robotic systems still lack this combination of abilities. Rather than focusing on better hardware, Sommer and Billard developed a control strategy for prioritizing the movement of individual digits and feedback from sensors, while limiting the applied force and remaining within the limits of joint movement. This makes it possible to construct a multitouch hand that can adaptively grasp an object at several points at once and probe with some digits while gently holding an object with the others. ![Figure][1] Strategically placed tactile sensors help a robotic hand grasp unknown objects while maintaining low contact forces. PHOTO: NICOLAS SOMMER, AUDE BILLARD, LASA-EPFL Rob. Auton. Syst. 10.1016/j.robot.2016.08.007 (2016). [1]: pending:yes

Multi-contact haptic exploration and grasping with tactile sensors

Haptic exploration has received a great deal of attention of late thanks to the variety of commercially available tactile sensors. While the majority of previous works consider control of a single contact point at a time, we tackle simultaneous control of multiple contact points on several links. In addition, we use information from the existing tactile signals to increase the number of points in contact. We demonstrate the usefulness of this form of control to speed up exploration, scanning and to compliantly grasp unknown objects. Our controller requires to know only the parts of the robot on which it is desirable to make contact and does not need a model of the environment besides the robot itself. We validate the algorithm in a set of experiments using a robotic hand covered with tactile sensors and arm. In a grasping application, the active adaptation of the fingers to the shape of the object ensures that the hand encloses the object with multiple contact points. We show that this improves the robustness of the grasp compared to simple enclosing strategies. When combined with an exploration strategy, our multi-contact approach offers an efficient use of tactile sensors on the whole surface of robotic fingers, and enables the robot to perform a rapid exploration of complex, non convex shapes while maintaining low contact forces. It is robust to variation in the approach angle and to changes in the geometry and orientation of the object.

A contact inspection system for aspheric optical components

We construct a contact inspection system and realize low contact force and high precision measurements for aspheric optical components. The inspection and calibration principles, as well as the reliability of the system are thoroughly studied. Our investigations show that the system could provide low contact force measurement (low than 0.7mN), fast scanning speed (2mm/s), and high accuracy (as low as 0.5μm), being a good option to the contact inspections of aspheric optical components.

Optimal Force-Time Integral for Pulmonary Vein Isolation According to Anatomical Wall Thickness Under the Ablation Line.

BackgroundLow contact force and force–time integral (FTI) during catheter ablation are associated with ineffective lesion formation, whereas excessively high contact force and FTI may increase the risk of complications. We sought to evaluate the optimal FTI for pulmonary vein (PV) isolation based on atrial wall thickness under the ablation line.Methods and ResultsContact force parameters and FTI during anatomical ipsilateral PV isolation for atrial fibrillation and atrial wall thickness were assessed retrospectively in 59 consecutive patients for their first PV isolation procedure. The PV antrum was divided into 8 segments, and the wall thickness of each segment under the ablation line was determined using multidetector computed tomography. The FTI for each ablation point was divided by the wall thickness of the PV antrum segment where each point was located to obtain FTI/wall thickness. In total, 5335 radiofrequency applications were delivered, and 85 gaps in PV isolation ablation lines and 15 dormant conductions induced by adenosine were detected. The gaps or dormant conductions were significantly associated with low contact force, radiofrequency duration, FTI, and FTI/wall thickness. Among them, FTI/wall thickness had the best prediction value for gaps or dormant conductions by receiver operating characteristic curve analysis. FTI/wall thickness of <76.4 gram‐seconds per millimeter (gs/mm) predicted gaps or dormant conductions with sensitivity (88.0%) and specificity (83.6%), and FTI/wall thickness of <101.1 gs/mm was highly predictive (sensitivity 97.0%; specificity 69.6%).Conclusions FTI/wall thickness is a strong predictor of gap and dormant conduction formation in PV isolation. An FTI/wall thickness ≈100 gs/mm could be a suitable target for effective ablation.

Active Head Motion Compensation of TMS Robotic System Using Neuro-Fuzzy Estimation

Transcranial Magnetic Stimulation (TMS) allows neuroscientist to study human brain behaviour and also become an important technique for changing the activity of brain neurons and the functions they sub serve. However, conventional manual procedure and robotized TMS are currently unable to precisely position the TMS coil because of unconstrained subject’s head movement and excessive contact force between the coil and subject’s head. This paper addressed this challenge by proposing an adaptive neuro-fuzzy force control to enable low contact force with a moving target surface. A learning and adaption mechanism is included in the control scheme to improve position disturbance estimation. The results show the ability of the proposed force control scheme to compensate subject’s head motions while maintaining desired contact force, thus allowing for more accurate and repeatable TMS procedures.

Fundamental investigation of micro-scale wear characteristics of ultra-fine gold wires under low contact force and long sliding distance

Micro-scale wear characteristics of ultra-fine gold wires with a diameter of ~28μm was investigated under a low contact force over a long sliding distance up to ~200km. The tip of the wire was slid against a silicon wafer under a low normal force of 5μN. Wear of the gold wire was quantified from the images of the tip obtained by a 3D laser microscope and a scanning electron microscope before and after the wear test. The dimensionless Archard relationship wear coefficient was in the order of 10−7 which was extremely low considering that sliding was carried out in dry condition. Such a low wear characteristics was attributed to low contact pressure that could be achieved by formation of a conformal contact due to flattening of the wire tip as sliding wear progressed. Wear behavior of the gold wire could be characterized by formation of thin flakes of wear debris that were generated as a result of adhesive shear stress imparted at the sliding interface. As an effort to reduce the wear coefficient even further, octadecyltrichlorosilane self-assembled monolayer was deposited on the silicon to serve as a nano-lubricant. It was effective in improving the wear resistance by about two-fold.

Clinical impact of contact force and its regional variability on efficiency and effectiveness of pulmonary vein isolation for atrial fibrillation

BackgroundThe purpose of this study is to analyze the impact of average contact force (CF) and its regional variability during pulmonary vein isolation (PVI) for atrial fibrillation (AF) on periprocedural parameters and midterm outcome. MethodsThis retrospective cohort study enrolled 57 drug-refractory AF patients who underwent initial PVI for AF using an open-irrigated CF catheter (SmartTouch Thermocool, Biosense Webster, Diamond Bar, CA, USA). Thirty patients were assigned to a lower CF (LCF) group (average CF≤10g) and 27 patients to a higher CF (HCF) group (average CF>10g). The relationship between CF and clinical outcome was analyzed. ResultsPatients were followed-up for 317±57 days after PVI. The CF was 8.1±1.3g in the LCF group and 12.4±1.5g in the HCF group. Higher average CF was associated with shorter ablation time (28±6min vs. 36±9min, p=0.0002) and lower radiofrequency energy delivery (79±18 vs. 99±26, p=0.0016) for PVI. The rate of acute PV reconnection (APVR) was similar in both groups (LCF group 60% vs. HCF group 44%, p=0.36). Four patients (13%) in the LCF group and nine patients (33%) in the HCF group experienced AF-recurrence. Average CF did not impact on AF-recurrence during midterm clinical outcome (p=0.09 by log-rank test). In the non-recurrence group (n=44), average CF was higher at left posterosuperior PV and right anteroinferior PV than that in the recurrence group (n=13) (p=0.012 and p=0.004, respectively). ConclusionsHigher average CF decreased ablation time and radiofrequency energy delivery for PVI, but did not decrease APVR rate or improve midterm clinical outcome.

Abstract 13509: A Prospective Randomized Study on the Prevalence, Characteristics, and Predictors of Pulmonary Vein Reconnections and the Clinical Outcomes Between Contact Force-Guided and Conventional Circumferential Pulmonary Vein Isolation of Atrial Fibrillation

Purpose: To prospectively investigate the differences in pulmonary vein reconnections (PVRs) and clinical outcomes between contact force (CF)-guided and conventional circumferential PV isolation (CPVI) of atrial fibrillation (AF). Methods: A total of 120 consecutive AF patients (63±10 years; 88 males) undergoing an initial CPVI were randomized to ablation with a target CF of 20g (CF-group; n=60) or that with operators blinded to the CF information (Blind-group; n=60). The right and left CPVI lines were each divided into 12 segments, and the occurrence of PVRs and CF-related parameters were evaluated in each segment. Time-dependent and adenosine-dependent PVRs were assessed twice during the procedure, just after completing the CPVI and at the end of the procedure. Results: The CF-group had significantly fewer PVRs (0.67±0.91/patient vs. 1.16±1.16/patient; P=0.007), a higher percentage of adenosine-dependent transient PVRs (60.5% vs. 28.8%; P=0.001), and lower percentage of persistent PVRs than the Blind-group. The mean CF was higher in the CF-group than in the Blind-group (Median, 18.0g vs. 16.1g; P&lt;0.001), with the most significant difference observed along the posterior right-sided PVs (P-RPVs) and anterior left-sided PVs (A-LPVs). In multiple logistic regression models, the mean CF was a negative predictor of PVRs along the P-RPVs and A-LPVs in the Blind-group (odds ratios, 0.728 and 0.786; P&lt;0.001 and 0.007), while no significant predictor was identified in the CF-group or along the anterior RPVs and posterior LPVs in the Blind-group. In the Kaplan-Meier analysis, the arrhythmia-free survival rate at 12 months was 91.2% in the CF-group (29.8% with antiarrhythmic drugs [AADs]) and 89.4% in the Blind-group (21.1% with AADs), respectively (P=0.596). Conclusions: CF-guided CPVI can reduce PVRs and result in a higher percentage of adenosine-dependent transient PVRs, and may be particularly beneficial along regions where a relatively low CF tends to be applied: the P-RPVs and A-LPVs. The comparable clinical outcomes may be due to (1) the learning curve effect obtained by the CF-guided technique, which improved the ablation electrode-tissue contact in the Blind-group, and (2) repeated provocation and elimination of dormant PV conduction.

Design and characterization of a resonant triaxial microprobe

A new trend for tactile microprobes leads to oscillating microprobes in order to overcome the drawbacks resulting from high Hertzian stress and disturbing surface forces. Thin water films on the measurement surface result in the so-called sticking effect which causes measurement faults such as snap-back and false triggering. This leads to measurement errors and low measurement speeds. We present an innovative oscillating triaxial microprobe which safely avoids sticking in all Cartesian measurement directions. The system design as well as the characterization of the microprobe are presented in this work. The low number of coupling elements, the batch-capable design and the low contact forces are the key features of the microprobe.

Randomized comparison of contact force-guided versus conventional circumferential pulmonary vein isolation of atrial fibrillation: prevalence, characteristics, and predictors of electrical reconnections and clinical outcomes.

We prospectively investigated the differences in pulmonary vein reconnections (PVRs) and clinical outcomes between contact force (CF)-guided and conventional circumferential PV isolation (CPVI) of atrial fibrillation (AF). One hundred twenty consecutive AF patients (63 ± 10 years; 88 males) undergoing an initial CPVI were randomized to ablation with a target CF of 20 g (CF group; n = 60) or that with operators blinded to the CF information (blind group; n = 60). The CF group had fewer PVRs (0.67 ± 0.91/patient vs. 1.16 ± 1.16/patient; P = 0.007), a lower incidence of persistent PVRs (13.2 vs. 41.2%; P < 0.001), and a shorter procedural time for the CPVI (50 vs. 56 min; P = 0.019) than the blind group. The mean CF was higher in the CF group than the blind group (18.0 vs. 16.1 g; P < 0.001), with the most significant difference observed along the posterior right-sided PVs (P-RPVs) and anterior left-sided PVs (A-LPVs). In logistic regression models, the mean CF was a negative predictor of PVRs along the P-RPVs and A-LPVs in the blind group (odds ratios, 0.728 and 0.786; P < 0.001 and 0.007), while no significant predictor was identified in the CF group or elsewhere in the blind group. In the Kaplan-Meier analysis, the arrhythmia-free survival rate at 12 months was 89.9% in the CF group and 88.2% in the blind group, respectively (P = 0.624). CF-guided CPVI can reduce PVRs and the procedural time and be particularly beneficial along regions where a relatively low CF tends to be applied: the P-RPVs and A-LPVs. The comparable clinical outcomes may be due to the learning curve effect obtained by the CF-guided technique and repeated provocation of dormant PV conduction.

The Effect of Contact Force in Atrial Radiofrequency Ablation: Electroanatomical, Cardiovascular Magnetic Resonance, and Histological Assessment in a Chronic Porcine Model

ObjectivesThis study sought to determine the effect of contact force (CF) on atrial lesion size, quality, and transmurality by using a chronic porcine model of radiofrequency ablation. BackgroundCF is a major determinant of ventricular lesion formation, but uncertainty exists regarding the most appropriate CF parameters to safely achieve permanent, transmural lesions in the atria. MethodsIntercaval linear ablation (30 W, 42°C, 17 ml/min irrigation) was performed in 8 Göttingen minipigs by using a force-sensing catheter with CF >20 g (high force) or <10 g (low force) at alternate ends of the line, separated by an intentional gap. Voltage mapping and cardiovascular magnetic resonance (CMR) imaging were performed pre-ablation, immediately after ablation, and at 2 months’ post-procedure. Lesions were sectioned orthogonal to the axis of ablation to assess transmurality. ResultsMean CF was 22.6 ± 11.4 g and 7.8 ± 4.0 g in the high and low CF regions. Acute tissue edema was greater with high CF, both caudally (7.0 mm vs. 4.6 mm; p = 0.016) and cranially (6.9 mm vs. 4.6 mm; p = 0.038). There was no difference in chronic lesion size (voltage mapping) or volume (late gadolinium enhancement CMR) between high and low CF regions. There was no difference in scar density (assessed by low-voltage criteria and late gadolinium enhancement signal intensity) or histological transmurality between high and low CF regions. ConclusionsAlthough high CF (>20 g) resulted in more acute tissue edema than low CF (<10 g), chronically there was no difference in lesion size, quality, or transmurality. Appropriate CF targets for atrial ablation may be lower than previously thought.

Influence of Contact Force on Electrochemical Responses of Redox Species Flowing in Nitrocellulose Membrane at Micropyramid Array Electrode.

In this study, we developed a micropyramid array electrode that facilitates contact between a nitrocellulose membrane and electrode, which is important to realize a quantitative and sensitive electrochemical detection system for immunochromatography. We evaluated the micropyamid array electrode with our newly developed detection system that can measure contact forces between a membrane and electrode, and also investigated the relationship between redox current and contact forces. By using normal pulse voltammetry, we observed higher reduction currents over a flat surface electrode at lower contact forces with the micropyramid array.