# Integrated Haptic Feedback with Augmented Reality to Improve Pinching and Fine Moving of Objects
## 2 Materials and Methods
### Experimental Trials  
At first, we evaluated the haptic latency with both devices. We measured the response time after stimulating the vibration tactile feedback. To visually evaluate these vibration  
Figure 3: (**a**) bHaptics Gloves covering the hand. (**b**) Rings worn on the index and thumb. delays, we attached a strip of paper to the haptic device, which moved during the vibration, and we changed the color of the Lego block after each touch detection. With both devices, we recorded a 60 Hz video using an Android phone camera through the HL2 display. Twelve users (8 males and 4 females) participated in the experiment. All of them with previous experience with the HL2. Eleven users are biomedical engineers at the University of Pisa, working full-time or part-time in the EndoCAS lab. Four of them have not yet graduated with their master's degrees, while the others hold positions as PhD students, postdoctoral researchers, or technicians. Additionally, one participant is in the army but has previously conducted several experiments in our lab. The study was conducted by the Declaration of Helsinki, approved by the Bioethics Committee of the University of Pisa (resolution n. 51/2024 of 27 September 2024). All the participants enrolled signed an informed consent that also included the consent to publish any media (photos and videos) from the trial. Before starting the experiment, they received both verbal and visual instructions on a PC running the same application uploaded in the HL2, outlining the tasks and the user interface functionalities. Once the experiment began with the HL2, no additional guidance was given. All participants performed the experiments using three different modalities: the bHaptics glove, the haptics ring, and bare hands. The starting order of the modalities was randomized as the execution order along the axes. As said, the timer started when a participant clicked on the button corresponding to the desired axis in the button array. The application recorded all user interactions, including timestamps, the number of trial actions required to complete the task (consisting of the number of pinching activations), and the distance error between the final position of the red cube with respect to the optimal one, and saved these data into an Excel file. Upon finishing the experiment, the participants completed a questionnaire consisting of 16 items based on a seven-point Likert scale ranging from \(-\)3 to +3, with 0 indicating a neutral response. The questionnaire was adapted from the ISO NORM 9241/110 standard for software usability evaluation [21]. To facilitate a more effective analysis, the responses were categorized into six groups: Software Usability and Effectiveness, User Interface, User Support, Learning Time, User Flexibility, Troubleshooting, Error Handling, and Adaptability. We also asked the users for their written opinion about both the applications and the devices. Statistical analyses were performed using IBM's SPSS software 22 on the collected responses. This included calculating the mean, median, standard error (SE), standard deviation (SD), and interquartile range (IQR). Additionally, the Shapiro-Wilk test was used to assess the normality of the data distribution. None of the experimental result datasets satisfied the normality assumption since their \(p\)-values were below 0.05. Consequently, we used a non-parametric test, specifically the Friedman test, to compare the three devices across three feedback modalities (number of trials, time, and distance error) to check for any significant differences. This approach was appropriate since our experimental design involved the same subjects testing the same application on different devices [22]. Based on the resulting \(p\)-values, if any were below 0.05 for a group test, a Wilcoxon Signed-Rank test was applied to identify where the significant differences lay between two different devices (Rings Vs bHaptics, Rings vs. Bare Hand, and bHaptics vs. Bare Hand).