The authors acknowledge the funding support from Canada&#39;s New Frontiers in Research Fund (NFRF), Natural Sciences&#160;and Engineering Research Council of Canada (NSERC) Discovery program, and Fonds de Recherche du Qu&#233;bec Nature et Technologies (FRQNT) master&#39;s training scholarships. The authors also would like to thank Prof. Yaoyao Zhao&#39;s group at McGill for their technical support on 3D printing of some components.

The mosquito species used for this protocol is an uninfected adult female Aedes aegypti (A. aegypti), received frozen and stored in a -20 &#176;C degree freezer. The species was provided by the NIH/NIAID Filariasis Research Reagent Resource Center for distribution through BEI Resources, NIAID, NIH: Uninfected Aedes aegypti, Strain Black Eye Liverpool (Frozen), NR-48920. The reagents and equipment used for the study are listed in the Table of Materials.
1. Dissecting the labium from the proboscis
<ol>
	<li>Using tweezers, place a dead mosquito on a glass slide under the microscope and ensure there is a tapered tip at the end of the proboscis (Figure 2A).</li>
	<li>While keeping the mosquito on the glass slide, place a scalpel blade gently over the labium near the mosquito&#39;s head (Figure 2B).</li>
	<li>Proceed to make an incision across the entire upper half of the labium (a cut of approximately 80 &#181;m) with a shallow penetration depth through the thickness of the labium. Ensure to apply a light pressure on the blade as to cut only the labium but not the fascicle that lies beneath.</li>
	<li>With a pair of tweezers, firmly hold the head of the mosquito, and with another pair of precision tweezers, lightly pinch the labium at any position in between the tapered tip and the location of the incision (Figure 2B).
	<ol>
		<li>Pull the tweezers holding the labium in the direction of the tapered tip (Figure 2C). Continue pulling the tweezers until the labium has ripped free and has been entirely removed from the fascicle.</li>
	</ol>
	</li>
	<li>Place the mosquito under the microscope and verify if the labrum&#39;s tip is present. This can be identified by the presence of a tapered tip on the fascicle (Figure 2D).</li>
</ol>
2. Separating the labrum&#39;s tip from the other fascicle members
<ol>
	<li>Clamp and close the tips of a set of precision tweezers and place the tip of the tweezers right beside the labrum near its tip.</li>
	<li>Use the tweezer tip to apply a gentle force on the labrum in the direction perpendicular to the length of the fascicle (Figure 3A).</li>
	<li>Continue pushing the labrum across the glass slide until separation of the labrum from the other fascicle members is achieved.</li>
	<li>Inspect the sample under the microscope to verify proper separation between the labrum and other fascicle members has been achieved (Figure 3, left). If separation is unsuccessful, refer back to step 2.1.</li>
</ol>
3. Cutting the labrum&#39;s tip
<ol>
	<li>While the labrum is still on the glass slide, place a scalpel blade over the labrum at approximately ~200 &#181;m in distance from the labrum&#39;s tip (Figure 4A). Gently apply sufficient pressure and cut the tip of the labrum all the way through. While the labrum tip should ideally be as short as possible, ~200 &#181;m is the best the current approach can handle.</li>
	<li>Measure the length of the cut labrum to ensure it is no longer than 300 &#181;m (Figure 4B) using any digital measurement software. In this protocol, ImageJ was used14.</li>
</ol>
4. Grabbing the tip of the labrum
<ol>
	<li>With a pair of precision tweezers, locate and isolate the labrum&#39;s tip on the glass slide. Discard every part remaining on the glass slide other than the labrum&#39;s tip.</li>
	<li>With the same precision tweezers, slowly and lightly pinch the labrum so that the cut end is free and unobstructed by the tweezers. Also, ensure the orientation of the labrum is parallel to the direction of the tweezers&#39; length and the cut end of the labrum is pointing away from the tweezers&#39; body.</li>
	<li>Once the specimen is firmly pinched, remove the clamping force holding the tweezers&#39; tips together. The labrum&#39;s tip will stick to one of the tweezers&#39; tips.</li>
	<li>Under a microscope, inspect the tweezers&#39; tips and ensure the labrum&#39;s tip is present on one of the tweezers&#39; tips (Figure 5). If the labrum&#39;s tip is not on the tweezers, refer back to step 4.2, and if the labrum&#39;s tip is not on the tweezers nor on the glass slide, refer back to step 1.</li>
</ol>
5. Applying epoxy on the tipless cantilever beam
<ol>
	<li>Place a drop (~0.05 mL) of epoxy on the edge of a new glass slide by directly drop-casting the adhesive from its original bottle/container. Place the epoxy-containing glass slide under the probe station and focus on it.</li>
	<li>Mount the tipless AFM cantilever to the clamp assembly by securing the base (i.e., the larger end), leaving the cantilever end free and suspended in space. Ensure that the bottom of the AFM cantilever is facing downward.</li>
	<li>Mount the manipulator onto the probe station.</li>
	<li>Raise the Z-axis of the manipulator to a position where the tipless cantilever is a few millimeters above the epoxy-containing glass slide.</li>
	<li>Manually move the manipulator such that the tipless cantilever is visible in the field view of the camera on the probe station.</li>
	<li>Using the manipulator, move the AFM cantilever along the X and Y directions until the tip of the cantilever is resting directly above the epoxy on the edge of the glass slide.</li>
	<li>Using the manipulator again, slowly lower the tipless cantilever in the Z direction over the edge of the glass slide.</li>
	<li>As the cantilever is lowered and approaches the glass slide, keep lowering the cantilever very slowly until it first touches the epoxy. Do not lower the cantilever any further.</li>
	<li>Cautiously, engage the manipulator to slowly move the cantilever in the X or Y direction and remove the cantilever from the pool of epoxy by continuously moving the cantilever in the selected direction until the cantilever is entirely separated from the epoxy on the glass slide. The tipless cantilever should have a miniature bubble of epoxy at its tip, visible under the probe station.</li>
	<li>Raise the cantilever in the Z-direction using the manipulator.</li>
</ol>
6. Bonding the labrum&#39;s tip to the tipless cantilever beam
<ol>
	<li>Rotate the manipulator about the cantilever&#39;s long axis by 90 degrees and rest the manipulator on the probe station on its side. In this configuration, the thicknesses along the length of the AFM cantilever is in the vertical direction.</li>
	<li>Position the precision tweezers that contain the labrum&#39;s tip under the probe station camera so that the entire length of the labrum&#39;s tip is visible on the computer monitor.</li>
	<li>Position the manipulator assembly holding the clamp and the tipless cantilever under the probe station camera so that the entire length of the tipless cantilever is visible on the computer monitor.</li>
	<li>Focus the probe station microscope on the labrum&#39;s tip and the tipless cantilever.</li>
	<li>Orient the cantilever perpendicularly to the labrum&#39;s tip by carefully and manually rotating the manipulator (Figure 6A).</li>
	<li>Using the degrees of freedom of the manipulator, slowly move the tipless cantilever in the XY directions such that the glue on the cantilever contacts the cut end of the labrum&#39;s tip (Figure 6B).</li>
	<li>Cure the epoxy, solidifying the intersection between the cantilever and mosquito labrum.</li>
	<li>Once the epoxy has cured, gently engage the manipulator in the XY directions and move the cantilever away from the tweezers, verifying that the labrum&#39;s tip is now standing on the tipless cantilever beam (Figure 6C).</li>
</ol>

Bio-Hybrid AFM Probe with Mosquito Labrum for Studying Biting Behaviors

<ol>
	<li>World Health Organization. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Global+vector+control+response+2017&#8211;2030.">Global vector control response 2017&#8211;2030.</a> World Health Organization. , (2017).</li><li>Gurera, D., Bhushan, B., Kumar, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Lessons+from+mosquitoes&#8217;+painless+piercing.">Lessons from mosquitoes&#8217; painless piercing.</a> J Mech Behav Biomed Mater. 84, 178-187 (2018).</li><li>Ma, G., Wu, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microneedle,+bio-microneedle+and+bio-inspired+microneedle:+A+review.">Microneedle, bio-microneedle and bio-inspired microneedle: A review.</a> Journ of Contr Relea. 251, 11-23 (2017).</li><li>Kong, X., Wu, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Micronano+structure+and+mechanics+behavior+of+mosquito&#8217;s+proboscis+biomaterials+with+applications+to+microneedle+design.">Micronano structure and mechanics behavior of mosquito&#8217;s proboscis biomaterials with applications to microneedle design.</a> Advan Mater Res. 299-300, 376-379 (2011).</li><li>Li, A. D. R., Putra, K. B., Chen, L., Montgomery, J. S., Shih, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mosquito+proboscis-inspired+needle+insertion+to+reduce+tissue+deformation+and+organ+displacement.">Mosquito proboscis-inspired needle insertion to reduce tissue deformation and organ displacement.</a> Sci Rep. 10 (1), 12248 (2020).</li><li>Meyer, E., Hug, H. J., Bennewitz, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Introduction+to+Scanning+Probe+Microscopy.">Introduction to Scanning Probe Microscopy.</a> Scanning Probe Microscopy. 1, 1-13 (2004).</li><li>Garc&#237;a, R., Per&#233;z, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dynamic+atomic+force+microscopy+methods.">Dynamic atomic force microscopy methods.</a> Surf Sci Rep. 47 (6), 197-301 (2002).</li><li>Thurner, P. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Atomic+force+microscopy+and+indentation+force+measurement+of+bone.">Atomic force microscopy and indentation force measurement of bone.</a> WIREs Nanomed and Nanobio. 1 (6), 624-649 (2009).</li><li>M&#252;ller, D. J., Dufr&#234;ne, Y. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Atomic+force+microscopy+as+a+multifunctional+molecular+toolbox+in+nanobiotechnology.">Atomic force microscopy as a multifunctional molecular toolbox in nanobiotechnology.</a> Nat Nanotech. 3 (5), 261-269 (2008).</li><li>Hussain, D., Ahmad, K., Song, J., Xie, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Advances+in+the+atomic+force+microscopy+for+-critical+dimension+metrology.">Advances in the atomic force microscopy for -critical dimension metrology.</a> Meas Sci Technol. 28 (1), 012001 (2017).</li><li>Kong, X. Q., Wu, C. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mosquito+proboscis:+An+elegant+biomicroelectromechanical+system.">Mosquito proboscis: An elegant biomicroelectromechanical system.</a> Phys Rev E. 82 (1), 011910 (2010).</li><li>Kong, X. Q., Wu, C. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Measurement+and+prediction+of+insertion+force+for+the+mosquito.">Measurement and prediction of insertion force for the mosquito.</a> J Bionic Eng. 6 (2), 143-152 (2009).</li><li>Ramasubramanian, M. K., Barham, O. M., Swaminathan, V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanics+of+a+mosquito+bite+with+applications+to+microneedle+design.">Mechanics of a mosquito bite with applications to microneedle design.</a> Bioinspir Biomim. 3 (4), 046001 (2008).</li><li>Dai, G., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nanoscale+surface+measurements+at+sidewalls+of+nano-+and+micro-structures.">Nanoscale surface measurements at sidewalls of nano- and micro-structures.</a> Measur Sci and Technol. 18 (2), 334-341 (2007).</li></ol>

Authors have no conflict of interest to declare.

Step 1 of the protocol is meant to clean the biological sample of the unwanted labium. To achieve this, an incision is made on the labium, but not on the fascicle, which rests directly beneath the labium (Figure 1). Because the fascicle and labium are not joined together at their interface (i.e., the labium is free to slide along the fascicle and is only kept in place by its attachment to the mosquito head), the performed incision is meant to separate part of the labium from the mosquito&#39...

World Health Organization (WHO) reported that vector-borne diseases (VBDs) account for over 17% of all infectious diseases, which cause more than 7,00,000 deaths per year globally. For example, as the deadliest animal in the world, mosquitoes spread numerous pathogens, such as dengue, malaria, and Zika, through blood-feeding arthropods, resulting in 700 million infections each year1. Explorations toward the development of effective measures to prevent VBDs are of crucial importance, including mimicking the penetration behaviors of mosquitoes to investigate their biting mechanisms and studies of potential barriers to prove their efficacy in preventing penetration. One key challenge is to develop proper approaches to perform such investigations. Efforts have been made in the literature, including the development of micro-scale needles that resemble the geometry of a mosquito stinger; however, many of the materials used to make these microneedles (i.e., viscoelastic materials2, silicon (Si), glass, ceramic3, etc.) have different mechanical properties than the biological material of the mosquito&#39;s proboscis. The engineered materials can be brittle and prone to fracture and buckling3,4, whereas the mosquito&#39;s proboscis can withstand fracture or buckling better4. The benefit of having a bio-hybrid probe using the labrum of a mosquito instead of engineered materials is that it can be a more accurate representation of the piercing mechanism of mosquitoes. Also, specialized tools must be integrated with micro needles to perform quantitative studies, such as the accurate measurement of force5, which is not easily achievable with customized setups using engineered microneedles.
Atomic force microscopy (AFM)-based approach is promising in that it operates by employing a cantilever with an ultra-fine tip that is carefully positioned close to a sample&#39;s surface. The tip can either scan across or be pressed towards/into a surface, experiencing varying attractive or repulsive forces due to its interactions with a sample6. These interactions lead to the cantilever&#39;s deflection, which is tracked by the reflection of a laser beam from the cantilever&#39;s top onto a photodetector6. The exceptional sensitivity to movement of the system enables AFM to conduct a diverse range of measurements, including but not limited to morphological mapping with picometer accuracy, force measurements ranging from piconewtons to micronewtons, and comprehensive multiphysics investigations7. For example, AFM indentations can be performed to precisely assess the response to the applied force of a sample and also to measure the hardness, elasticity, and other mechanical properties of a sample by coupling with appropriate analytical models8. The probe of the AFM is most commonly made of silicon (Si) or silicon nitride (Si3N4)8 with a length of 20-300 &#181;m9 and a tip radius on the order of several to tens of nanometers10. The nanometer scale tip radius can be ideal for applications such as high-resolution imaging; however, it does not possess the characteristics of biological stingers for studies that try to mimic penetration behaviors in terms of stiffness, radius, shape, and aspect ratio. For example, the microneedle structure of a mosquito is the fascicle, which has an aspect ratio of ~6011 (length ~1.5 mm to 2 mm; diameter ~30 &#181;m)12. While a conventional AFM probe can be assumed to resemble a biological stinger like a labrum, its distinct material properties and dimensions will not reflect the real situation during a bite.
To enable quantitative investigations of penetration behaviors mimicking biological bites of insects or other animals with stingers, here, a process to fabricate bio-hybrid AFM cantilevers with a biological stinger as its tip is developed. As a case study, an AFM cantilever with a mosquito labrum&#39;s tip attached was successfully demonstrated. Harnessing existing information from literature on the typical insertion forces that a mosquito uses to pierce through a victim&#39;s skin12,13, this bio-hybrid AFM cantilever can potentially allow near-real mimicry of mosquito bites under a regular AFM. The protocol of leveraging micro biological stingers to fabricate bio-hybrid AFM cantilevers can also be applied to the development of other sharp stinger-based biohybrid AFM cantilevers for quantitative investigations of a variety of biting mechanisms.
Terminologies 
A schematic of a proboscis and its components of interest are shown in Figure 1, and their definitions are (1) Proboscis: a body part from the mouth of a mosquito that allows the mosquito to feed itself, with a core-shell structure composed of the fascicle(core) and the labium(shell), (2) Labium: the dark and blunt outer cover of a proboscis2, (3) Fascicle: a group of slender needles contained inside of the labium, including two maxillae, two mandibles, a hypopharynx, and a labrum2, (4) Hypopharynx: responsible for secreting saliva into the host&#39;s bloodstream2, (5) Maxillae: serrated member assisting in the feeding mechanism2, (5) Mandibles: similar to the maxilla, they help the mosquito in the feeding mechanism and have a sharp tip2, (6) Labrum: the main member for penetrating the skin of a victim, which is much bigger than the maxillae, mandibles and hypopharynx. It also has sensory structures that allow it to find blood vessels and internal channels under the skin2, (7) Manipulator: an assembly with three degrees of freedom and micron-scale accuracy for positioning, allowing movement in XYZ directions, (8) Clamp assembly: a custom-made 2-part clamp mounted to the manipulator used to clamp the tipless AFM cantilever during the experiment.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>&#160;5-SA-SE Straight Tapered Ultra Fine-Pointed Tweezers</td>
			<td>Excelta</td>
			<td>N/A</td>
			<td>For manipulating/dissecting the proboscis.</td>
		</tr>
		<tr>
			<td>C-4D Probe station</td>
			<td>Everbeing Int&#8217;l Corp&#160;</td>
			<td>N/A</td>
			<td>Used for AFM assembly.</td>
		</tr>
		<tr>
			<td>Tipless Tapping Mode Cantilever</td>
			<td>NanoAndMore USA</td>
			<td>TL-NCH</td>
			<td>AFM cantilever used for mounting the labrum. 
			Specs are shown here: 
			 
			Shape: Beam 
			Force Constant: 42 N/m (10 - 130 N/m) 
			Resonance Frequency: 330 kHz (204 - 497 kHz) 
			Length: 125 &#181;m (115 - 135 &#181;m) 
			Width: 30 &#181;m (22.5 - 37.5 &#181;m) 
			Thickness: 4 &#181;m ( 3 - 5 &#181;m)</td>
		</tr>
		<tr>
			<td>UV Expoxy</td>
			<td>Let&#39;s resin</td>
			<td>ALR00146</td>
			<td>For stinger attachment.</td>
		</tr>
	</tbody>
</table>

development of a bio-hybrid mosquito stinger-based atomic force microscopy probe

Mosquitoes, notorious as the deadliest animals to humans due to their capacity to transmit diseases, pose a persistent challenge to public health. The primary prevention strategy currently in use involves chemical repellents, which often prove ineffective as mosquitoes rapidly develop resistance. Consequently, the invention of new preventive methods is crucial. Such development hinges on a thorough understanding of mosquito biting behaviors, necessitating an experimental setup that accurately replicates actual biting scenarios with controllable testing parameters and quantitative measurements. To bridge this gap, a bio-hybrid atomic force microscopy (AFM) probe was engineered, featuring a biological stinger - specifically, a mosquito labrum - as its tip. This bio-hybrid probe, compatible with standard AFM systems, enables a near-authentic simulation of mosquito penetration behaviors. This method marks a step forward in the quantitative study of biting mechanisms, potentially leading to the creation of effective barriers against vector-borne diseases (VBDs) and opening new avenues in the fight against mosquito-transmitted illnesses.

Scanning electron microscopy (SEM) images of the fabricated bio-hybrid AFM probe can be found in Figure 7. The end of the labrum was successfully glued to the tipless cantilever beam. Due to the natural curvature of mosquito stingers and the manual operation of the presented protocol, it is extremely difficult to obtain a cantilever with a stinger tip perfectly perpendicular to the cantilever. The off-center angle between the stinger and an imaginary center line perpendicular to the cantilev...

Watch this Scientific Journal Video about Author Spotlight: Development of Bio-Hybrid AFM Cantilevers for Quantitative Analysis of Mosquito Biting Mechanisms at JoVE.com

Author Spotlight: Development of Bio-Hybrid AFM Cantilevers for Quantitative Analysis of Mosquito Biting Mechanisms

Quantitative and controlled investigations into insect biting behaviors are crucial for devising effective strategies to combat vector-borne diseases. In this context, a method for fabricating a bio-hybrid atomic force microscopy (AFM) probe is introduced.

Development of a Bio-Hybrid Mosquito Stinger-Based Atomic Force Microscopy Probe

Mosquitoes, notorious as the deadliest animals to humans due to their capacity to transmit diseases, pose a persistent challenge to public health. The ...

development-bio-hybrid-mosquito-stinger-based-atomic-force-microscopy

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662 Views.  McGill University. Quantitative and controlled investigations into insect biting behaviors are crucial for devising effective strategies to combat vector-borne diseases. In this context, a method for fabricating a bio-hybrid atomic force microscopy (AFM) probe is introduced.

Video: Author Spotlight: Development of Bio-Hybrid AFM Cantilevers for Quantitative Analysis of Mosquito Biting Mechanisms

Scanning-probe Single-electron Capacitance Spectroscopy

The integration of low-temperature scanning-probe techniques and single-electron capacitance spectroscopy represents a powerful tool to study the electronic quantum structure of small systems - including individual atomic dopants in semiconductors. Here we present a capacitance-based method, known as Subsurface Charge Accumulation (SCA) imaging, which is capable of resolving single-electron charging while achieving sufficient spatial resolution to image individual atomic dopants. The use of a capacitance technique enables observation of subsurface features, such as dopants buried many nanometers beneath the surface of a semiconductor material1,2,3. In principle, this technique can be applied to any system to resolve electron motion below an insulating surface.
As in other electric-field-sensitive scanned-probe techniques4, the lateral spatial resolution of the measurement depends in part on the radius of curvature of the probe tip. Using tips with a small radius of curvature can enable spatial resolution of a few tens of nanometers. This fine spatial resolution allows investigations of small numbers (down to one) of subsurface dopants1,2. The charge resolution depends greatly on the sensitivity of the charge detection circuitry; using high electron mobility transistors (HEMT) in such circuits at cryogenic temperatures enables a sensitivity of approximately 0.01 electrons/Hz&frac12; at 0.3 K 5.

Scanning-probe single-electron capacitance spectroscopy facilitates the study of single-electron motion in localized subsurface regions. A sensitive charge-detection circuit is incorporated into a cryogenic scanning probe microscope to investigate small systems of dopant atoms beneath the surface of semiconductor samples.

The integration of low-temperature scanning-probe techniques and single-electron capacitance spectroscopy represents a powerful tool to study the ...

Atomic Force Microscopy of Red-Light Photoreceptors Using PeakForce Quantitative Nanomechanical Property Mapping

Atomic force microscopy (AFM) uses a pyramidal tip attached to a cantilever to probe the force response of a surface. The deflections of the tip can be measured to ~10 pN by a laser and sectored detector, which can be converted to image topography. Amplitude modulation or &#8220;tapping mode&#8221; AFM involves the probe making intermittent contact with the surface while oscillating at its resonant frequency to produce an image. Used in conjunction with a fluid cell, tapping-mode AFM enables the imaging of biological macromolecules such as proteins in physiologically relevant conditions. Tapping-mode AFM requires manual tuning of the probe and frequent adjustments of a multitude of scanning parameters which can be challenging for inexperienced users. To obtain high-quality images, these adjustments are the most time consuming.
PeakForce Quantitative Nanomechanical Property Mapping (PF-QNM) produces an image by measuring a force response curve for every point of contact with the sample. With ScanAsyst software, PF-QNM can be automated. This software adjusts the set-point, drive frequency, scan rate, gains, and other important scanning parameters automatically for a given sample. Not only does this process protect both fragile probes and samples, it significantly reduces the time required to obtain high resolution images. PF-QNM is compatible for AFM imaging in fluid; therefore, it has extensive application for imaging biologically relevant materials.
The method presented in this paper describes the application of PF-QNM to obtain images of a bacterial red-light photoreceptor, RpBphP3 (P3), from photosynthetic R. palustris in its light-adapted state. Using this method, individual protein dimers of P3 and aggregates of dimers have been observed on a mica surface in the presence of an imaging buffer. With appropriate adjustments to surface and/or solution concentration, this method may be generally applied to other biologically relevant macromolecules and soft materials.

A method for investigating the structure of a protein photoreceptor using atomic force microscopy (AFM) is described in this paper. PeakForce Quantitative Nanomechanical Property Mapping (PF-QNM) reveals intact protein dimers on a mica surface.

Atomic force microscopy (AFM) uses a pyramidal tip attached to a cantilever to probe the force response of a surface. The deflections of the tip can be ...

Preparation and Friction Force Microscopy Measurements of Immiscible, Opposing Polymer Brushes

Solvated polymer brushes are well known to lubricate high-pressure contacts, because they can sustain a positive normal load while maintaining low friction at the interface. Nevertheless, these systems can be sensitive to wear due to interdigitation of the opposing brushes. In a recent publication, we have shown via molecular dynamics simulations and atomic force microscopy experiments, that using an immiscible polymer brush system terminating the substrate and the slider surfaces, respectively, can eliminate such interdigitation. As a consequence, wear in the contacts is reduced. Moreover, the friction force is two orders of magnitude lower compared to traditional miscible polymer brush systems. This newly proposed system therefore holds great potential for application in industry. Here, the methodology to construct an immiscible polymer brush system of two different brushes each solvated by their own preferred solvent is presented. The procedure how to graft poly(N-isopropylacrylamide) (PNIPAM) from a flat surface and poly(methyl methacrylate) (PMMA) from an atomic force microscopy (AFM) colloidal probe is described. PNIPAM is solvated in water and PMMA in acetophenone. Via friction force AFM measurements, it is shown that the friction for this system is indeed reduced by two orders of magnitude compared to the miscible system of PMMA on PMMA solvated in acetophenone.

The methodology to perform friction force microscopy experiments for contacting brushes is presented: Two polymer brushes that are grafted from (a) substrates and (b) colloidal probes are slid to show that, by using two contacting immiscible brush systems, friction in sliding contacts is reduced compared to miscible brush systems.

Solvated polymer brushes are well known to lubricate high-pressure contacts, because they can sustain a positive normal load while maintaining low ...

Investigating Single Molecule Adhesion by Atomic Force Spectroscopy

Atomic force spectroscopy is an ideal tool to study molecules at surfaces and interfaces. An experimental protocol to couple a large variety of single molecules covalently onto an AFM tip is presented. At the same time the AFM tip is passivated to prevent unspecific interactions between the tip and the substrate, which is a prerequisite to study single molecules attached to the AFM tip. Analyses to determine the adhesion force, the adhesion length, and the free energy of these molecules on solid surfaces and bio-interfaces are shortly presented and external references for further reading are provided. Example molecules are the poly(amino acid) polytyrosine, the graft polymer PI-g-PS and the phospholipid POPE (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine). These molecules are desorbed from different surfaces like CH3-SAMs, hydrogen terminated diamond and supported lipid bilayers under various solvent conditions. Finally, the advantages of force spectroscopic single molecule experiments are discussed including means to decide if truly a single molecule has been studied in the experiment.

A protocol to couple a large variety of single molecules covalently onto an AFM tip is presented. Procedures and examples to determine the adhesion force and free energy of these molecules on solid supports and bio-interfaces are provided.

Atomic force spectroscopy is an ideal tool to study molecules at surfaces and interfaces. An experimental protocol to couple a large variety of single ...

Probing C84-embedded Si Substrate Using Scanning Probe Microscopy and Molecular Dynamics

This paper reports an array-designed C84-embedded Si substrate fabricated using a controlled self-assembly method in an ultra-high vacuum chamber. The characteristics of the C84-embedded Si surface, such as atomic resolution topography, local electronic density of states, band gap energy, field emission properties, nanomechanical stiffness, and surface magnetism, were examined using a variety of surface analysis techniques under ultra, high vacuum (UHV) conditions as well as in an atmospheric system. Experimental results demonstrate the high uniformity of the C84-embedded Si surface fabricated using a controlled self-assembly nanotechnology mechanism, represents an important development in the application of field emission display (FED), optoelectronic device fabrication, MEMS cutting tools, and in efforts to find a suitable replacement for carbide semiconductors. Molecular dynamics (MD) method with semi-empirical potential can be used to study the nanoindentation of C84-embedded Si substrate. A detailed description for performing MD simulation is presented here. Details for a comprehensive study on mechanical analysis of MD simulation such as indentation force, Young&#39;s modulus, surface stiffness, atomic stress, and atomic strain are included. The atomic stress and von-Mises strain distributions of the indentation model can be calculated to monitor deformation mechanism with time evaluation in atomistic level.

Probing C84-embedded Si Substrate Using Scanning Probe Microscopy and Molecular Dynamics

This paper reports the nanomaterial fabrication of a fullerene Si substrate inspected and verified by nanomeasurements and molecular dynamic simulation.

This paper reports an array-designed C84-embedded Si substrate fabricated using a controlled self-assembly method in an ultra-high vacuum chamber. The ...

Sub-nanometer Resolution Imaging with Amplitude-modulation Atomic Force Microscopy in Liquid

Atomic force microscopy (AFM) has become a well-established technique for nanoscale imaging of samples in air and in liquid. Recent studies have shown that when operated in amplitude-modulation (tapping) mode, atomic or molecular-level resolution images can be achieved over a wide range of soft and hard samples in liquid. In these situations, small oscillation amplitudes (SAM-AFM) enhance the resolution by exploiting the solvated liquid at the surface of the sample. Although the technique has been successfully applied across fields as diverse as materials science, biology and biophysics and surface chemistry, obtaining high-resolution images in liquid can still remain challenging for novice users. This is partly due to the large number of variables to control and optimize such as the choice of cantilever, the sample preparation, and the correct manipulation of the imaging parameters. Here, we present a protocol for achieving high-resolution images of hard and soft samples in fluid using SAM-AFM on a commercial instrument. Our goal is to provide a step-by-step practical guide to achieving high-resolution images, including the cleaning and preparation of the apparatus and the sample, the choice of cantilever and optimization of the imaging parameters. For each step, we explain the scientific rationale behind our choices to facilitate the adaptation of the methodology to every user's specific system.

We present a method for achieving sub-nanometer resolution images with amplitude-modulation (tapping mode) atomic force microscopy in liquid. The method is demonstrated on commercial atomic force microscopes. We explain the rationale behind our choices of parameters and suggest strategies for resolution optimization.

Atomic force microscopy (AFM) has become a well-established technique for nanoscale imaging of samples in air and in liquid. Recent studies have shown ...

Measurement of Quantum Interference in a Silicon Ring Resonator Photon Source

Silicon photonic chips have the potential to realize complex integrated quantum information processing circuits, including photon sources, qubit manipulation, and integrated single-photon detectors. Here, we present the key aspects of preparing and testing a silicon photonic quantum chip with an integrated photon source and two-photon interferometer. The most important aspect of an integrated quantum circuit is minimizing loss so that all of the generated photons are detected with the highest possible fidelity. Here, we describe how to perform low-loss edge coupling by using an ultra-high numerical aperture fiber to closely match the mode of the silicon waveguides. By using an optimized fusion splicing recipe, the UHNA fiber is seamlessly interfaced with a standard single-mode fiber. This low-loss coupling allows the measurement of high-fidelity photon production in an integrated silicon ring resonator and the subsequent two-photon interference of the produced photons in a closely integrated Mach-Zehnder interferometer. This paper describes the essential procedures for the preparation and characterization of high-performance and scalable silicon quantum photonic circuits.

Silicon photonic chips have the potential to realize complex integrated quantum systems. Presented here is a method for preparing and testing a silicon photonic chip for quantum measurements.

Silicon photonic chips have the potential to realize complex integrated quantum information processing circuits, including photon sources, qubit ...

Atomic Layer Deposition of Vanadium Dioxide and a Temperature-dependent Optical Model

Vanadium dioxide is a material that has a reversible metal-insulator phase change near 68 &#176;C. To grow VO2 on a wide variety of substrates, with wafer-scale uniformity and angstrom level control of thickness, the method of atomic-layer deposition was chosen. This ALD process enables high-quality, low-temperature (&#8804;150 &#176;C) growth of ultrathin films (100-1000 &#197;) of VO2. For this demonstration, the VO2 films were grown on sapphire substrates. This low temperature growth technique produces mostly amorphous VO2 films. A subsequent anneal in an ultra-high vacuum chamber with a pressure of 7x10-4 Pa of ultra-high purity (99.999%) oxygen produced oriented, polycrystalline VO2 films. The crystallinity, phase, and strain of the VO2 were determined by Raman spectroscopy and X-ray diffraction, while the stoichiometry and impurity levels were determined by X-ray photoelectron spectroscopy, and finally the morphology was determined by atomic force microscopy. These data demonstrate the high-quality of the films grown by this technique. A model was created to fit to the data for VO2 in its metallic and insulating phases in the near infrared spectral region. The permittivity and refractive index of the ALD VO2 agreed well with the other fabrication methods in its insulating phase, but showed a difference in its metallic state. Finally, the analysis of the films&#39; optical properties enabled the creation of a wavelength- and temperature-dependent model of the complex optical refractive index for developing VO2 as a tunable refractive index material.

Thin films (100-1000 &#197;) of vanadium dioxide (VO2) were created by atomic-layer deposition (ALD) on sapphire substrates. Following this, the optical properties were characterized through the metal-insulator transition of VO2. From the measured optical properties, a model was created to describe the tunable refractive index of VO2.

Vanadium dioxide is a material that has a reversible metal-insulator phase change near 68 &#176;C. To grow VO2 on a wide variety of substrates, with ...

Electroantennography-based Bio-hybrid Odor-detecting Drone using Silkmoth Antennae for Odor Source Localization

Small drones with chemical or biosensor devices that can detect airborne odorant molecules have attracted considerable attention owing to their applicability in environmental and security monitoring and search-and-rescue operations. Small drones with commercial metal-oxide-semiconductor (MOX) gas sensors have been developed for odor source localization; however, their real-time-odor-detection performance has proven inadequate. However, biosensing technologies based on insect olfactory systems exhibit relatively high sensitivity, selectivity, and real-time response with respect to odorant molecules compared to commercial MOX gas sensors. In such devices, excised insect antennae function as portable odorant biosensor elements and have been found to deliver excellent sensing performance. This study presents experimental protocols for odorant-molecule detection in the air using a small autonomous bio-hybrid drone based on a mountable electroantennography (EAG) device incorporating silkmoth antennae.
We developed a mountable EAG device including sensing/processing parts with a Wi-Fi module. The device was equipped with a simple sensor enclosure to enhance the sensor directivity. Thus, odor source localization was conducted using the spiral-surge algorithm, which does not assume an upwind direction. The experimental bio-hybrid odor-detecting drone identified real-time odorant-concentration differences in a pseudo-open environment (outside a wind tunnel) and localized the source. The developed drone and associated system can serve as an efficient odorant molecule-detection tool and a suitable flight platform for developing odor source localization algorithms owing to its high programmability.

This study introduces experimental protocols for a bio-hybrid odor-detecting drone based on silkmoth antennae. The operation of an experimental electroantennogram device with silkmoth antennae is presented, in addition to the structure of a bio-hybrid drone designed for odor source localization using the spiral-surge algorithm.

Small drones with chemical or biosensor devices that can detect airborne odorant molecules have attracted considerable attention owing to their ...

Co-localizing Kelvin Probe Force Microscopy with Other Microscopies and Spectroscopies: Selected Applications in Corrosion Characterization of Alloys

Kelvin probe force microscopy (KPFM), sometimes referred to as surface potential microscopy, is the nanoscale version of the venerable scanning Kelvin probe, both of which measure the Volta potential difference (VPD) between an oscillating probe tip and a sample surface by applying a nulling voltage equal in magnitude but opposite in sign to the tip-sample potential difference. By scanning a conductive KPFM probe over a sample surface, nanoscale variations in surface topography and potential can be mapped, identifying likely anodic and cathodic regions, as well as quantifying the inherent material driving force for galvanic corrosion.
Subsequent co-localization of KPFM Volta potential maps with advanced scanning electron microscopy (SEM) techniques, including back scattered electron (BSE) images, energy dispersive spectroscopy (EDS) elemental composition maps, and electron backscattered diffraction (EBSD) inverse pole figures can provide further insight into structure-property-performance relationships. Here, the results of several studies co-localizing KPFM with SEM on a wide variety of alloys of technological interest are presented, demonstrating the utility of combining these techniques at the nanoscale to elucidate corrosion initiation and propagation.
Important points to consider and potential pitfalls to avoid in such investigations are also highlighted: in particular, probe calibration and the potential confounding effects on the measured VPDs of the testing environment and sample surface, including ambient humidity (i.e., adsorbed water), surface reactions/oxidation, and polishing debris or other contaminants. Additionally, an example is provided of co-localizing a third technique, scanning confocal Raman microscopy, to demonstrate the general applicability and utility of the co-localization method to provide further structural insight beyond that afforded by electron microscopy-based techniques.

Kelvin probe force microscopy (KPFM) measures surface topography and differences in surface potential, while scanning electron microscopy (SEM) and associated spectroscopies can elucidate surface morphology, composition, crystallinity, and crystallographic orientation. Accordingly, the co-localization of SEM with KPFM can provide insight into the effects of nanoscale composition and surface structure on corrosion.

Kelvin probe force microscopy (KPFM), sometimes referred to as surface potential microscopy, is the nanoscale version of the venerable scanning Kelvin ...