title: Combining Hydromorphic and Shape-Shifting Effects for Programmable Passive Actuation in 4D-Printed Biocomposites

authors: Bachmann, Phil Aron

abstract: 4D printing involves the fabrication of structures that respond dynamically to external stimuli. While various actuation mechanisms have been extensively studied, the integration of multiple actuation effects remains relatively unexplored. This study examines the combined influence of hydromorphic and shape-shifting effects in a biocomposite containing 40 wt% cellulose fibres. The biocomposite was combined with polylactide (PLA) and processed via 3D printing to produce bi-material strips, which were then comprehensively analysed for their material properties and shape-changing behaviour. Upon immersion in water, the biocomposite expanded by 3.2 % perpendicular to the printing direction and exhibited a marked decrease in Young’s modulus with increasing water content. Bi-material strips 1 mm thick displayed pronounced hydromorphic behaviour, achieving maximum curvatures of 0.036 - 0.052 mm-1 depending on the passive-to-active layer thickness ratio. Thicker strips (4 mm) reached 0.012 mm-1 under the same conditions. When both heat and water were applied as external stimuli, the biocomposite and neat PLA layers became simultaneously active, and curvatures of up to 0.057 mm⁻¹ were obtained for 4 mm strips. This curvature surpassed the hydromorphic-only and shape-shifting-only responses by factors of 4.77 and 1.82, respectively. The results demonstrate that integrating water- and heat-induced stimuli increases achievable curvature and accelerates the response, enabling high-curvature deformations even in relatively thick structures. The approach therefore holds promise for applications that demand significant shape transformations without compromising structural integrity.

text: Combining Hydromorphic and Shape-Shifting Effects for Programmable Passive Actuation in 4D-Printed Biocomposites 4D printing involves the fabrication of structures that respond dynamically to external stimuli. While various actuation mechanisms have been extensively studied, the integration of multiple actuation effects remains relatively unexplored. This study examines the combined influence of hydromorphic and shape-shifting effects in a biocomposite containing 40 wt% cellulose fibres. The biocomposite was combined with polylactide (PLA) and processed via 3D printing to produce bi-material strips, which were then comprehensively analysed for their material properties and shape-changing behaviour. Upon immersion in water, the biocomposite expanded by 3.2 % perpendicular to the printing direction and exhibited a marked decrease in Young’s modulus with increasing water content. Bi-material strips 1 mm thick displayed pronounced hydromorphic behaviour, achieving maximum curvatures of 0.036 - 0.052 mm-1 depending on the passive-to-active layer thickness ratio. Thicker strips (4 mm) reached 0.012 mm-1 under the same conditions. When both heat and water were applied as external stimuli, the biocomposite and neat PLA layers became simultaneously active, and curvatures of up to 0.057 mm⁻¹ were obtained for 4 mm strips. This curvature surpassed the hydromorphic-only and shape-shifting-only responses by factors of 4.77 and 1.82, respectively. The results demonstrate that integrating water- and heat-induced stimuli increases achievable curvature and accelerates the response, enabling high-curvature deformations even in relatively thick structures. The approach therefore holds promise for applications that demand significant shape transformations without compromising structural integrity.

year: 2025

title: Comparison of changes in electroencephalographic measures during induction of general anaesthesia: influence of the gamma frequency band and electromyogram signal

authors: Sleigh, James W.

subjects: monitoring

abstract: Recent research has shown that high-frequency, gamma-band electroencephalographic (EEG) oscillations (40–60 Hz) may be an important marker of the conscious state. We compared the ability of the bispectral index (BIS) to distinguish the awake and anaesthetized states during the induction of general anaesthesia with: (i) components of the BIS (BetaRatio, SynchFastSlow); (ii) a new EEG variable—the median frequency of the first time derivative of the EEG signal (SE50d); and (iii) the SE50d derived from an EEG signal that has had the frequencies above 30 Hz removed (SE50d30Hz). Two groups of subjects were studied: (i) nine volunteers undergoing a short propofol infusion until loss of response to verbal command, and (ii) 84 patients undergoing routine anaesthesia for a variety of surgical procedures. In the volunteer group, the changes in the BetaRatio and SE50d were comparable with changes in the BIS. The changes in the SE50d30Hz were less consistent. In the patient group, the BIS components were equivalent to the BIS in separating the awake from the surgically anaesthetized states (area under receiver operating curve: BIS 0.95, SE50d 0.95, BetaRatio 0.96). Using the submental electromyogram (EMG) signal to estimate the frontalis EMG (30–47 Hz) signal, the changes in EMG signal were, on average, about one-tenth the magnitude of the EEG. We conclude that: (i) there exist simpler derived EEG variables that are similar in accuracy to the BIS; (ii) it is important to avoid filtering out the EEG frequencies above 30 Hz; and (iii) in most patients the confounding effects of the frontalis EMG on the EEG are minimal.

text: Comparison of changes in electroencephalographic measures during induction of general anaesthesia: influence of the gamma frequency band and electromyogram signal Recent research has shown that high-frequency, gamma-band electroencephalographic (EEG) oscillations (40–60 Hz) may be an important marker of the conscious state. We compared the ability of the bispectral index (BIS) to distinguish the awake and anaesthetized states during the induction of general anaesthesia with: (i) components of the BIS (BetaRatio, SynchFastSlow); (ii) a new EEG variable—the median frequency of the first time derivative of the EEG signal (SE50d); and (iii) the SE50d derived from an EEG signal that has had the frequencies above 30 Hz removed (SE50d30Hz). Two groups of subjects were studied: (i) nine volunteers undergoing a short propofol infusion until loss of response to verbal command, and (ii) 84 patients undergoing routine anaesthesia for a variety of surgical procedures. In the volunteer group, the changes in the BetaRatio and SE50d were comparable with changes in the BIS. The changes in the SE50d30Hz were less consistent. In the patient group, the BIS components were equivalent to the BIS in separating the awake from the surgically anaesthetized states (area under receiver operating curve: BIS 0.95, SE50d 0.95, BetaRatio 0.96). Using the submental electromyogram (EMG) signal to estimate the frontalis EMG (30–47 Hz) signal, the changes in EMG signal were, on average, about one-tenth the magnitude of the EEG. We conclude that: (i) there exist simpler derived EEG variables that are similar in accuracy to the BIS; (ii) it is important to avoid filtering out the EEG frequencies above 30 Hz; and (iii) in most patients the confounding effects of the frontalis EMG on the EEG are minimal.

year: 2001

title: Reconnecting whānau: Pathways to recovery for Māori with bipolar disorder

authors: Waitoki, Waikaremoana

subjects: mental health

abstract: While Māori are known to experience a higher burden of mental health and addiction problems compared to non-Māori (Baxter, 2008), little exploratory research has been conducted into Māori experiences of bipolar affective disorder. Bipolar disorder is at times regarded as a “life sentence”, with little hope of recovery. The recovery- focused mental health literature, however, argues wellness is achievable for even the most intractable conditions (Lapsley, Nikora, & Black, 2002; Mental Health Commission, 2001). The aim of this research was to gather information about the experiences of Māori who were diagnosed with bipolar affective disorder. Interviews were conducted with 22 Māori wāhine (women) and tāne (men), and using thematic analyses, themes relevant to their life stories were uncovered. This research sought to contribute to the realisation of Māori potential by explicitly shifting from deficit- focused frameworks to a focus on systemic factors that influenced Māori wellbeing. Highlights were that whānau (participants) who were connected with friends, partners and family were motivated to achieve wellness and to stay well.

text: Reconnecting whānau: Pathways to recovery for Māori with bipolar disorder While Māori are known to experience a higher burden of mental health and addiction problems compared to non-Māori (Baxter, 2008), little exploratory research has been conducted into Māori experiences of bipolar affective disorder. Bipolar disorder is at times regarded as a “life sentence”, with little hope of recovery. The recovery- focused mental health literature, however, argues wellness is achievable for even the most intractable conditions (Lapsley, Nikora, & Black, 2002; Mental Health Commission, 2001). The aim of this research was to gather information about the experiences of Māori who were diagnosed with bipolar affective disorder. Interviews were conducted with 22 Māori wāhine (women) and tāne (men), and using thematic analyses, themes relevant to their life stories were uncovered. This research sought to contribute to the realisation of Māori potential by explicitly shifting from deficit- focused frameworks to a focus on systemic factors that influenced Māori wellbeing. Highlights were that whānau (participants) who were connected with friends, partners and family were motivated to achieve wellness and to stay well.

year: 2015