Black May, or Bloody May (Thai: พฤษภาทมิฬ; RTGS:Phruetsapha Thamin) is a common name for the 17–20 May 1992 popular protest in Bangkok against the government of General Suchinda Kraprayoon and the military crackdown that followed. Up to 200,000 people demonstrated in central Bangkok at the height of the protests. The military crackdown resulted in 52 officially confirmed deaths, many disappearances, hundreds of injuries, and over 3,500 arrests. Many of those arrested are alleged to have been tortured.
Background
On 23 February 1991, Army Commander Suchinda Kraprayoon overthrew the democratically elected but openly corrupt government of Chatichai Choonhavan. The coup-makers, who called themselves the National Peace Keeping Council (NPKC), appointed Anand Panyarachun as prime minister. Anand's interim government promulgated a new constitution and scheduled parliamentary elections for 22 March 1992.
A government coalition with 55 percent of the lower house was formed and appointed General Suchinda as prime minister. Massive public protests immediately followed. On 9 May, Suchinda responded by saying he would support a constitutional amendment making individuals who had not been elected to parliament ineligible for the premiership. Tensions dissipated, but the truce was short-lived.
Popular protests
On 17 May 1992 the two leading government parties announced that although they supported the constitutional amendment, they also favoured transitional clauses that would permit Suchinda to serve as prime minister for the term of the parliament. It became clear the government parties would not honour their word, and plans went ahead for a strike on Sunday, 17 May.[1]
17 May
Obviously concerned about the people's mounting anger, the interior minister ordered provincial governors to prevent people from travelling to Bangkok to join the rally.[1] Suchinda threatened to sack the governor of Bangkok for allegedly assisting the anti-government rallies of the previous week, while the army hastily arranged a competing "Anti-Drought Musical Festival" to be held at the Army Auditorium.[2] Radio stations were banned from playing recordings by several popular singers who had voiced their support for the demonstrations.[3]
Nevertheless, the rally was the biggest since the downfall of the Thanom regime in October 1973. At its peak, 200,000 people filled Sanam Luang, overflowing onto the encircling streets.[1][4] At about 20:30, Chamlong Srimuang Sudarat Keyuraphan and Dr. San Hatthirat led the protesters on a two-kilometre march to Government House, to demand Suchinda's resignation.[5] As they reached the intersection of Rachadamnoen and Rachadamnoen Nok Avenues, they were halted at Phan Fa Bridge, which had been barricaded with razor wire by the police. At 23:00 a group of demonstrators attempted to break through the barricade, but were repulsed by water cannons from four fire trucks blocking the way. The protesters then tried to commandeer one of the fire trucks, but were beaten back by riot police armed with batons. Protesters replied with stones and Molotov cocktails.[1][5] Chamlong used a loudspeaker to urge the marchers not to attack the police, but his words were ignored. In this initial clash, about 100 protesters and 21 policemen were injured.[1]
18 May
By midnight two fire engines had been set on fire, and the situation was spiralling out of control. Some 700 troops had been called in and the fighting fanned out from Phan Fa Bridge. At 00:30 Suchinda declared a state of emergency, making gatherings of more than ten persons illegal. The government urged people to go home. Hospitals in the area were already receiving the injured, including four with gunshot wounds who died that night.[1] Chamlong remained near Phan Fa Bridge and nearby Democracy Monument. At about 04:00, soldiers threatened the nearly 40,000 protesters by firing M16 rifles into the air. An hour and a half later, they began firing again. By the morning, the army brought in more troops, and crowds grew larger in other sections of the city.
Early on the afternoon of 18 May, Suchinda publicly accused Chamlong of fomenting violence and defended the government's use of force. Shortly thereafter, troops firing continuously in the air moved in to surround Chamlong. He was handcuffed and arrested.
However, the crowds still did not disperse, and violence escalated. When government troops secured the area around Phan Fa Bridge and Democracy Monument, protests shifted to Ramkhamhaeng University in the east of the city. By the evening of 19 May, about 50,000 people had gathered there.
Royal intervention

Early on the morning of 20 May, Princess Sirindhorn addressed the country on television, calling for an end to the violence. Her appeal was rebroadcast throughout the day. That evening, her brother, Crown Prince Vajiralongkorn, broadcast a similar appeal.
Finally, at 21:30, a television broadcast of King Bhumibol Adulyadej, Suchinda, and Chamlong was shown, in which the King demanded that the two men put an end to their confrontation and work together through parliamentary procedures. In the broadcast, the King addressed the two generals:[6]
The Nation belongs to everyone, not one or two specific people. The problems exist because we don't talk to each other and resolve them together. The problems arise from 'bloodthirstiness'. People can lose their minds when they resort to violence. Eventually, they don't know why they fight each other and what the problems they need to resolve are. They merely know that they must overcome each other and they must be the only winner. This no way leads to victory, but only danger. There will only be losers, only the losers. Those who confront each other will all be the losers. And the loser of the losers will be the Nation.... For what purpose are you telling yourself that you're the winner when you're standing upon the ruins and debris?.
Suchinda then released Chamlong and announced an amnesty for protesters. He also agreed to support an amendment requiring the prime minister to be elected. Chamlong asked the demonstrators to disperse, which they did. On 24 May 1992, Suchinda resigned as Prime Minister of Thailand.
Press censorship
The front page of the International Herald Tribune's 20 May 1992 issue was blacked out with felt tip pen, as was an editorial of the Bangkok Post of the same date, though other articles relating to the demonstrations remained untouched. The English-language newspaper The Nation and two Thai-language newspapers were shut down on 21 May though the order was rescinded a few hours later.[7]
Aftermath

The violence resulted in 39 reported deaths,[8] hundreds of injuries, and many disappearances. Security forces "...intentionally fired on and killed many unarmed demonstrators and inflicted savage and gratuitous beating on hundreds of others."[8]:42 Over 3,500 people were arrested.
A House of Representatives Special Committee and a fact-finding committee led by Sophon Rattanakorn shared the same conclusion: the government of General Suchinda used excessive force to crack down on the rally. Some facts from the investigation, such as names of military officers and military units responsible for rounding up, killing, and torturing of protesters were revealed to the public. It is believed these facts were recorded in the report of the Ministry of Defense (Thailand)'s Fact Finding Committee led by General Pichit Kullawanit, but it is still kept from the Thai public. The military constitution of 1992 remained in place until 1997, when a replacement was drafted and promulgated.

Chamlong later apologized for his role in the events: "I wanted a peaceful rally," he said. "I can't deny some responsibility for the damage and loss of life. I feel deeply sorry for those families whose members were killed in the incident, for those people who were injured and their families." Nevertheless, he noted, "We were right in what we have done."  He then retired from politics, eventually to return during the protests against the government of Thaksin Shinawatra.
Suchinda was later appointed chairman of Telecom Asia (today known as True Corporation), a company which received a concession to install two million telephone lines in Bangkok during the Anand government. Anand later became Chairman of Saha-Union Group, which had received an independent power producer concession during his government.
See also
The 2010 Thai military crackdown dubbed Savage May by Thai media.

Further reading

 — a brief timeline of Black May

Southeast Asian Ministers of Education Organization,
Physicians for Human Rights,


This article is concerned with Bertha Pappenheim as the patient Anna O. For her life before and after her treatment, see Bertha Pappenheim.

Anna O. was the pseudonym of a patient of Josef Breuer, who published her case study in his book Studies on Hysteria, written in collaboration with Sigmund Freud. Her real name was Bertha Pappenheim (1859–1936), an Austrian-Jewish feminist and the founder of the Jüdischer Frauenbund (League of Jewish Women).
Anna O. was treated by Breuer for severe cough, paralysis of the extremities on the right side of her body, and disturbances of vision, hearing, and speech, as well as hallucination and loss of consciousness. She was diagnosed with hysteria. Freud implies that her illness was a result of the resentment felt over her father's real and physical illness that later led to his death.[1]
Her treatment is regarded as marking the beginning of psychoanalysis. Breuer observed that whilst she experienced 'absences' (a change of personality accompanied by confusion), she would mutter words or phrases to herself. In inducing her to a state of hypnosis, Breuer found that these words were "profoundly melancholy fantasies...sometimes characterized by poetic beauty". Free association came into being after Anna/Bertha decided  (with Breuer's input) to end her hypnosis sessions and merely talk to Breuer, saying anything that came into her mind.  She called this method of communication "chimney sweeping", and this served as the beginning of free association.
Historical records since showed that when Breuer stopped treating Anna O. she was not becoming better but progressively worse.[2] She was ultimately institutionalized: "Breuer told Freud that she was deranged; he hoped she would die to end her suffering".[3]
She later recovered over time and led a productive life. The West German government issued a postage stamp in honour of her contributions to the field of social work.[4]

According to one perspective, "examination of the neurological details suggests that Anna suffered from complex partial seizures exacerbated by drug dependence."[5] In this view, her illness was not, as Freud suggested, psychological, but neurological. Professor of psychology Hans Eysenck and medical historian Elizabeth M. Thornton argued that it was caused by tuberculous meningitis. While some believe that Freud misdiagnosed her, and she in fact suffered from temporal lobe epilepsy, and many of her symptoms, including imagined smells, are common symptoms of types of epilepsy, others meticulously refute these claims.[6]
Illness
Bertha's father fell seriously ill in mid-1880 during a family holiday in Ischl. This event was a turning point in her life. While sitting up at night at his sickbed she was suddenly tormented by hallucinations and a state of anxiety.[7] Her illness later developed a wide spectrum of symptoms:
Language disorders (aphasia): on some occasions she could not speak at all, sometimes she spoke only English, or only French, or Italian. She could however always understand German. The periods of aphasia could last for days, and sometimes varied with the time of day.
Neuralgia: she suffered from facial pain which was treated with morphine and chloral and led to addiction. The pain was so severe that surgical severance of the trigeminus nerve was considered.
Paralysis (paresis): signs of paralysis and numbness occurred in her limbs, primarily on only one side. Although she was right-handed, she had to learn to write with her left hand because of this condition.
Visual impairments: she had temporary motor disturbances in her eyes. She perceived objects as being greatly enlarged and she squinted.
Mood swings: Over long periods she had daily swings between conditions of anxiety and depression, followed by relaxed states.
Amnesia: when she was in one of these states she could not remember events or any of her own actions which took place when she was in the other state.
Eating disorders: in crisis situations she refused to eat. During one hot summer she rejected liquids for weeks and lived only on fruit.
Pseudocyesis: she underwent symptoms of a false pregnancy. When in analysis with Freud, she accused Breuer of impregnating her, which however was merely imagined.
At first the family did not react to these symptoms, but in November 1880 a friend of the family, the physician Josef Breuer, began to treat her. He encouraged her, sometimes under light hypnosis, to narrate stories, which led to partial improvement of the clinical picture, although her overall condition continued to deteriorate. Starting on 11 December Bertha Pappenheim was bedridden for several months.
Death of her father
Bertha Pappenheim's father died on 5 April 1881. As a result, she became fully rigid and did not eat for days. Her symptoms continued to get worse and on 7 June she was admitted against her will to the Inzersdorf sanatorium, where she remained until November. After returning she continued to be treated by Breuer. She returned to this sanatorium several times over the course of the following years (sometimes at her own wish).
According to Breuer, the slow and laborious progress of her "remembering work" in which she recalled individual symptoms after they had occurred, thus "dissolving" them, came to a conclusion on 7 June 1882 after she had reconstructed the first night of hallucinations in Ischl. "She has fully recovered since that time" were the words with which Breuer concluded his case report.[8]
Bellevue Sanatorium

On 12 July 1882, Breuer referred Pappenheim to the private Bellevue Clinic in Kreuzlingen on Lake Constance, which was headed by Robert Binswanger. After treatment in Bellevue she was no longer personally treated by Breuer.
While in Kreuzlingen she visited her cousins Fritz Homburger and Anna Ettlinger in Karlsruhe. The latter was one of the founders of the Karlsruhe High School for Girls (Mädchengymnasium), which was attended by the young Rahel Straus. Ettlinger engaged in literary work. In an article which appeared in 1870 entitled "A Discussion of Women’s Rights" (Ein Gespräch über die Frauenfrage) she demanded equal education rights for women. She also gave private lessons, and organized "ladies’ literature courses".
Pappenheim read aloud to her some of the stories she had written, and her cousin, 14 years her senior, encouraged her to continue her literary activities.[9] During this visit toward the end of 1882 Pappenheim also participated in a training course for nurses which was offered by the Women's Association of Baden (Badischer Frauenverein). The purpose of this training was to qualify young ladies to head nursing institutions. She could not finish the course before her visit came to an end.
On 29 October 1882 her condition improved and she was released from treatment in Kreuzlingen. In the following years, about which little is known, she lived a quiet life with her mother in Vienna. There is evidence of three stays at Inzersdorf during this time; her sickness was not conquered.
Despite her illness, Pappenheim was a strong personality. Breuer describes her as a woman "of considerable intelligence, astonishingly astute reasoning and sharp-sighted intuition [...]”.[10]

Pappenheim became known to the general public under the pseudonym of Miss "Anna O.", a patient of Breuer. Her case history was described in Studies on Hysteria (Studien über Hysterie) (1895), which Breuer published together with Freud. She is presented as the first case in which it was possible to "thoroughly investigate" hysteria and cause its symptoms to disappear. Her statement that being able to verbalize her problem helped her to unburden herself is in accordance with the treatment later denoted in psychoanalysis as the "catharsis theory". Accordingly, Freud described her as the "actual founder of the psychoanalytic approach". Based on this case study the assertion that "those with hysteria suffer for the most part from their reminiscences", in other words from traumatic memories which can be "processed" by relating them, was formulated for the first time.[11]
Freud wrote:

Breuer’s findings are still today the foundation of psychoanalytic therapy. The statement that symptoms disappear with awareness of their unconscious preconditions has been confirmed by all subsequent research […].[12]

Freud specified psychoanalytic "therapy," but not theory.  Psychoanalysis did not come into being until  "Interpretation of Dreams" was written five years later.
Sources
Aspects of the Anna O. case were first published by Freud and Breuer in 1893 as preliminary communications in two Viennese medical journals. The detailed case history appeared in 1895 in Studies on Hysteria.
The name Anna O. was constructed by shifting her initials "B.P." one letter back in the alphabet to  "A.O."
When the first volume of Ernest Jones’ Freud biography appeared in 1953, in which the Anna O. of the studies was identified as being Bertha Pappenheim, her friends and admirers were outraged; they only knew her from her time in Frankfurt. One of the reasons for Dora Edinger's biography was to contrast her identification as being "mentally ill", which at the time was considered defamatory, with a depiction of Pappenheim as a philanthropist and advocate of women's rights.
Jones' portrayal contained further details, especially legends about the conclusion of Breuer's treatment, but except for the information contained in the studies nothing was known about the further course of her illness. New facts only became known based on research by Henri Ellenberger and subsequently by Albrecht Hirschmüller, who were able to find Breuer's case history of Pappenheim and other documents in the archives of the Bellevue Clinic in Kreuzlingen.[13]
Those of Freud's letters to his fianceé Martha Bernays which have been published contain a few hints about the course of Pappenheim's therapy and Freud's relationship to Breuer, but until all of Freud's letters are published there is room for speculation.[14]
Treatment
Breuer began the therapy without a clear method or theoretical basis. The treatment of her symptoms ranged from feeding her when she rejected food to dosages of chloral when she was agitated.
He described his observations as follows:

She had two completely separate states of consciousness which alternated quite often and suddenly, and in the course of her illness became more and more distinct. In the one state she was sad and apprehensive, but relatively normal. In the other state she had hallucinations and "misbehaved", that is, she swore, threw pillows at people, […] etc.[15]

He noted that when in one condition she could not remember events or situations that had occurred in the other condition. He concluded, "it is difficult to avoid saying that she dissolved into two personalities, one of which was psychically normal and the other mentally ill."[16]
Such symptoms are associated with the clinical picture of what, at the time of her treatment, was referred to as "split personality" and today is referred to as "dissociative identity disorder." The existence and frequency of such an illness was, and still is, controversial.
A first therapy approach was suggested by the observation that the patient calmed down and her speech disorder improved whenever she was asked to tell stories that had presumably arisen from her daydreams. About these daydreams Breuer remarked: "Although everyone thought she was present, she was living in a fantasy, but as she was always present when addressed, nobody suspected it." [17] He also encouraged her to calmly "reel off" these stories by using such prompts as a first sentence. The formula he used was always the same: "There was a boy…" At times Pappenheim could only express herself in English, but usually understood the German spoken around her. About her descriptions Breuer said, "The stories, always sad, were sometimes quite nice, similar to Andersen’s 'Picture Book Without Pictures'".[18]
The patient was aware of the relief that "rattling off" brought her, and she described the process using the terms "chimney-sweeping" and "talking cure". The latter formulation subsequently became part of psychoanalytic terminology.
Other levels of story telling soon came up, and were combined with and penetrated each other. Examples include:
Stories from a "private theater"
Hallucinatory experiences
Temporal relocation of episodes: during one phase her experience of the illness was shifted by one year
Episodes of occurrence of hysterical symptoms
Breuer developed systematic remembering and "reeling off" the occasions when hysterical symptoms first occurred into a therapeutic method first applied to Pappenheim. To his surprise he noticed that a symptom disappeared after the first occurrence was remembered, or after the cause was "excavated".
Breuer described his final methodology as follows: In the morning he asked Pappenheim under light hypnosis about the occasions and circumstances under which a particular symptom occurred. When he saw her in the evening, these episodes—there were sometimes over 100—were systematically "reeled off" by Pappenheim in reverse temporal order. When she got to the first occurrence and thus to the "cause", the symptoms appeared in an intensified form and then disappeared "forever".
This therapy came to a conclusion when they had worked their way back to a "black snake" hallucination which Pappenheim experienced one night in Ischl when she was at her father's sickbed. Breuer describes this finish as follows:

In this way all the hysteria came to an end. The patient herself had made a firm resolution to finish the business on the anniversary of her transfer to the countryside. For that reason she pursued the "talking cure" with great energy and animation. On the final day she reproduced the anxiety hallucination which was the root of all her illness and in which she could only think and pray in English, helped along by rearranging the room to resemble her father's sickroom. Immediately thereafter she spoke German and was then free of all the innumerable individual disorders which she had formerly shown.[19]

Conclusion of treatment
A legend arose about the conclusion of Pappenheim's treatment by Josef Breuer. It was handed down in slightly different versions by various people; one version is contained in a letter from Freud to Stefan Zweig:

I was in a position to guess what really happened with Br’s patient long after we parted company when I recalled a communication from Br dating from the time before our joint work and relating to another context, and which he never repeated. That evening, after all her symptoms were overcome, he was again called to her, and found her confused and writhing with abdominal cramps. When asked what was the matter she responded, "Now the child I have from Dr. Br. is coming". At that moment he had in his hand the key which would open the way to the Mothers, but he dropped it. With all his intellectual talents he was devoid of anything Faustian. He took flight in conventional horror and passed on the patient to a colleague. She struggled for months in a sanatorium to regain her health./ I was so sure of my reconsruction that I published it somewhere. Br’s younger daughter (who was born shortly after the conclusion of that therapy, which is not irrelevant as to a meaningful connection) read my portrayal and asked her father about it (this was shortly before his death). He confirmed my analysis, which she later relayed to me.[20]

As nothing is known of such a publication by Freud, it is not clear where Breuer's daughter could have read it. In the version by Ernest Jones, after his flight Breuer quickly goes on a second honeymoon to Vienna with his wife Mathilda, who actually conceives a child there—in contrast to the imaginary child of Bertha Pappenheim. There is no evidence for any of this, and most of it has been proved false. Breuer did not flee but rather  referred his patient to Kreuzlingen. He did not go to Vienna but with his family on a summer vacation to Gmunden, and he did not conceive a child (either in Vienna or in Gmunden), since his youngest child—Dora Breuer—was born on 11 March 1882, three months before the alleged conception.
Freud's purpose in describing the conclusion of treatment in a way that contradicts some of the verifiable facts is unclear. The assumption that he wanted to make himself the sole discoverer of psychoanalysis at Breuer's expense is contradicted by the description of the discovery in Freud's writings, in which he does not minimize Breuer's role, but rather emphasizes it. Freud's behavior is compared by some authors with his conduct in the so-called "cocaine affair". There, too, he gave false representations not only privately, but also several times in published form, without there being any advantage to offset the risk of lasting damage to his scientific reputation.
Breuer later described the therapy as "a trial by ordeal", probably in the sense of an examination. It claimed of him over 1,000 hours in the course of two years.
Success of treatment
After Breuer ceased treating her, both he and Freud continued to follow the course of Pappenheim's illness.[21] Among Freud's disciples the dubiousness of the assertion of “treatment success” was discussed. In a private seminar Carl Gustav Jung said in 1925:

So the famous first case he treated together with Breuer and which was vastly praised as an outstanding therapeutic success was nothing of the sort.[22]

And Charles Aldrich reports:

But in this famous case the patient was not healed. Freud told Jung that all her old symptoms returned after he had given up the case.[23]

Opponents of psychoanalysis use this statement as an argument against this therapeutic approach.
How Pappenheim herself assessed the success of her treatment is not documented.[24] She never spoke about this episode of her life and vehemently opposed any attempts at psychoanalytic treatment of people in her care.[25]
In popular culture
Aspects of Bertha Pappenheim's biography (especially her role as Breuer's patient) were treated in the film Freud: The Secret Passion by John Huston (along with elements of other early psychoanalytic case histories). The film is based on a screenplay by Jean-Paul Sartre who, however, distanced himself from the film version.
Josef Breuer's treatment of Anna O. is portrayed in When Nietzsche Wept.
Modern interpretations
Since Anna O.'s treatment in the 1800s, current research has suggested many illnesses she might have suffered from. Many believe that the illness was not psychological as Freud suggested but either neurological or organic. Medical researcher Elizabeth Thornton, after interviewing many of Freud's early patients, suggested that Anna O. had suffered from tuberculous meningitis.[26] Others have suggested it was encephalitis, a form of brain inflammation.[27] Many have also suggested that she suffered from a form of temporal lobe epilepsy since many of her symptoms, including imagined smells, are common symptoms of types of epilepsy.[5][6][27]
See also

Bertha Pappenheim
Conversion disorder
Hypnoid state
Somatic symptom disorder
Wolf man
Rat man
Little Hans
Dora (case study)

Further reading
Aubin, Melissa. , University of Toronto.
Mikkel Borch-Jacobsen, , (Routledge, 1996)


Self-cleaning surfaces are a class of materials with the inherent ability to remove any debris or bacteria from their surfaces in a variety of ways. The self-cleaning functionality of these surfaces are commonly inspired by natural phenomena observed in lotus leaves, gecko feet, and water striders to name a few. The majority of self-cleaning surfaces can be placed into three categories: 1) Superhydrophobic, 2) Superhydrophilic, and 3) Photocatalytic.
History
The first instance of a self-cleaning surface was created in 1995.[1] Paz et al. created a transparent titanium dioxide (TiO2) film that was used to coat glass and provide the ability for the glass to self-clean. The first commercial application of this self-cleaning surface, Pilkington Activ, was developed by Pilkington glass in 2001. This product implements a two-stage cleaning process. The first stage consists of photocatalysis of any fouling matter on the glass. This stage is followed by the glass becoming superhydrophilic and allowing water to wash away the catalyzed debris on the surface of the glass. Since the creation of self-cleaning glass, titanium dioxide has also been used to create self-cleaning nanoparticles that can be incorporated into other material surfaces to allow them to self-clean.[2]
Surface characteristics
The ability of a surface to self-clean commonly depends on the hydrophobicity or hydrophilicity of the surface. Whether cleaning aqueous or organic matter from a surface, water plays an important role in the self-cleaning process. Specifically, the contact angle of water on the surface is an important characteristic that helps determine the ability of a surface to self-clean. This angle is affected by the roughness of the surface and the following models have been developed to describe the "stickiness" or wettability of a self-cleaning surface.
Young's model

Young and colleagues proposed Young's model of wetting that relates the contact angle of a water droplet on a flat surface to the surface energies of the water, the surface, and the surrounding air. This model is typically an oversimplification of a water droplet on an ideally flat surface. This model has been expanded upon to consider surface roughness as a factor in predicting water contact angle on a surface. Young's model is described by the following equation:

c
o
s
(

θ

0

)
=

(

γ

S
A

−

γ

S
L

γ

L
A

)

{\displaystyle cos(\theta _{0})=\left({\frac {\gamma _{SA}-\gamma _{SL}}{\gamma _{LA}}}\right)}

[3]

θ

0

{\displaystyle \theta _{0}}

 = Contact angle of water on the surface

γ

S
A

{\displaystyle \gamma _{SA}}

= Surface energy of the surface-air interface

γ

S
L

{\displaystyle \gamma _{SL}}

= Surface energy of surface-liquid interface

γ

L
A

{\displaystyle \gamma _{LA}}

= Surface energy of liquid-air interface
Wenzel's model
When a water droplet is on a surface that is not flat and the surface topographical features lead to a surface area that is larger than that of a perfectly flat version of the same surface, the Wenzel model is a more accurate predictor of the wettability of this surface. Wenzel's model is described by the following equation:

c
o
s
(
θ
)
=

R

f

c
o
s
(

θ

0

)

{\displaystyle cos(\theta )=R_{f}cos(\theta _{0})}

[3][4]

θ

{\displaystyle \theta }

 = Contact angle of water predicted by Wenzel's model

R

f

{\displaystyle R_{f}}

 = Ratio of surface area of rough surface to the surface area of a flat projection of the same surface
Cassie-Baxter's model
For more complex systems that are representative of water-surface interactions in nature, the Cassie-Baxter model is used. This model takes into consideration the fact that a water droplet may trap air between itself and the surface that it is on. The Cassie-Baxter model is described by the following equation:

c
o
s
(

θ

C
B

)
=

R

f

c
o
s
(

θ

0

)
−

f

L
A

(

R

f

c
o
s
(

θ

0

)
+
1
)

{\displaystyle cos(\theta _{CB})=R_{f}cos(\theta _{0})-f_{LA}(R_{f}cos(\theta _{0})+1)}

[3][5]

θ

C
B

{\displaystyle \theta _{CB}}

 = Contact angle of water predicted by Cassie-Baxter's model

f

L
A

{\displaystyle f_{LA}}

 = Liquid-air fraction, the fraction of the liquid droplet that is in contact with air
Mechanisms
Use of water

Control over surface wettability is a critical aspect of self-cleaning surfaces. Both superhydrophobic and superhydrophilic surfaces have been used as self-cleaning materials.
Superhydrophobic
Superhydrophobic surfaces can be created in a number of different ways including plasma or ion etching, crystal growth on a material surface, and nanolithography to name a few.[6] All of these processes create nano-topographical features which imbue a surface with superhydrophobicity. The ultimate goal in developing superhydrophobic surfaces is to recreate the self-cleaning properties of the Lotus Leaf that has the inherent ability to repel all water in nature. The basis for superhydrophobic self-cleaning is the ability of these surfaces to prevent water from spreading out when in contact with the surface. This is reflected in a water contact angle nearing 180 degrees. Superhydrophobic self-cleaning surfaces also have low sliding angles which allows for water that is collected on the surface to easily be removed, commonly by gravity. While superhydrophobic surfaces are great for removing any water-based debris, these surfaces likely will not be able to clean away other types of fouling matter such as oil.
Superhydrophilic

Superhydrophilicity allows for surfaces to clean away a wide variety of dirt or debris. This mechanism is very different than the aforementioned superhydrophobic surfaces. For superhydrophilic self-cleaning surfaces, cleaning occurs because water on the surface is able to spread out to a great degree (extremely low water contact angle) to get between any fouling debris and the surface to wash away the debris.
Photocatalysis
One of the most commonly used self-cleaning products, titanium dioxide, utilizes a unique self-cleaning mechanism that combines an initial photocatalytic step and subsequent superhydrophilicity. A titanium dioxide coating, typically on glass windows, when exposed to UV light, will generate free electrons that will interact with oxygen and water in the air to create free radicals. These free radicals will in turn breakdown any fouling organic matter deposited on the surface of the glass. Titanium dioxide also changes the normally hydrophobic glass to a superhydrophilic surface. Thus, when rainfall occurs, instead of water beading up on the window surface and instantly falling down the glass, rain drops will rapidly spread out on the hydrophilic surface. The water will then move down the surface of the window, as a film rather than a droplet, essentially acting like a squeegee to remove surface debris.
In nature
Plants
Lotus leaf
The lotus flower has been known as a symbol of purity in some Asian cultures.[7] The lotus leaves (Nelumbo nucifera) are water-repellent and poorly adhesive which keep them free from contamination or pollution even being immersed in dirty water. This ability, called self-cleaning, shows that Nature shields itself from dirt and pathogens and self-cleaning plays a vital role in the resistance towards invading microbes. Indeed, numerous spores and conidia of pathogenic life forms, mainly fungi, need aqua for germination and taint leaves within the sight of water.[8] It had been a curiosity how lotus flower could remain clean even in muddy water, until German botanists, Barthlott and Neinhuis, introduced the unique dual structure of leaves with the help of a scanning electron microscopy (SEM).[9][10] Papillose epidermis cells carpet the exterior of a plant, particularly the leaf. These cells generate papillae or microasperties which make surface very rough. On top of microscale roughness, the papillae surface is superimposed with nanoscale asperities consisting of three-dimensional (3-D) hydrophobic hydrocarbons: epicuticular waxes.  Basically, the plant cuticle is a composite material composed of a network of cutin and low surface energy waxes, designed at different hierarchical levels.[11][12][13] The various leveled surface of lotus leaves is made out of convex cells (looks like bumps) and a much smaller layer of waxy tubules.[14] The water beads on plant leaves rest on the apex of the nanofeatures since air is enclosed in the valley of convex cells which minimizes the contact area of water droplet. Hence, the lotus leaves represent remarkable superhydrophobicity. Static contact angle and contact angle hysteresis of the lotus leaf are determined around 164° and 3°, respectively.[15] With small tilting angles, water droplets on the leaf roll off and take any dirt or contaminant along, leading to self-cleaning.[16]
In plants world, the lotus leaf is not the only example of natural superhydrophobic surfaces. For instance, taro (Colocasia esculenta) leaves were found to exhibit self-cleaning behavior, too.[17] They have a binary roughness built up by averagely 10mm elliptical protrusions in diameter and nano-sized pins. India canna (Cannageneralis bailey) leaves and the rice leaves (whatever the kind of rice) also represent superhydrophobicity, arising from the hierarchical surface morphology.[18]
Nepenthes pitcher plants
The Nepenthes carnivorous pitcher, widespread in a lot of countries such as, India, Indonesia, Malaysia and Australia, possesses a superhydrophilic surface, on which wetting angle approaches to zero to create uniform water film. Therefore, it increases the slipperiness of the surface and the prey slides off from its rims (peristome).[19]  Surface topography of Nepenthes rim demonstrates multiple scale radial ridges. The second order ridges are quite small in size and generated by straight rows of overlapping epidermidis cells. The surface of epidermidis cells are smooth and wax-free. The absence of wax crystals and microscopic roughness enhance the hydrophilicity and capillary forces, in doing so, water can swiftly wet the surface of rim.[20]
Animals
Butterfly wings
Butterfly wings possess not only ultra-hydrophobic trait but also directional adhesive characteristics. If the water bead is along the radial outward (RO) direction from the body’s central axis, it rolls off and cleans the dirt away, leading to self-cleaning. On the other hand, if droplets stand against the opposite direction, they are pinned at the surface, leading adhesion and securing the flight stability of the butterfly by preventing deposit of dirt on the wings near the center of the body. SEM micrographs of wings exhibit hierarchy along the RO direction, arising from aligned microgrooves, covered by fine lamella-stacking nanostripes.[21]
Water striders (Gerris remigis)
Water striders (Gerris remigis), most commonly called Jesus bugs, have an extraordinary ability that lets them walk on the water. In a fashion similar to superhydrophobic plants, their legs are highly water repellent due to their hierarchical morphology. They are built up with hydrophobic waxy microhairs, microsetae, and each hair is covered with nanogrooves. As a result, air is entrapped between micro- and nanohairs, which repels water.[22] Feng et al. measured how deep the leg can dip into water and the contact angle of the leg. They found the contact angle at least 168° and the maximum depth reported 4.38 ± 0.02mm.[23]
Gecko feet
Gecko feet are the most famous reversible adhesion mechanism in nature. The anti-fouling ability of feet allows geckos to run on dusty ceilings and corners without the accumulation of dirt on their feet. In 2000, Autumn et al. revealed the origin of gecko’s strong adhesion by investigating the surface features of the toes under electron microscope.[24]  They observed a hierarchical morphology of each foot which is composed of millions of small hair called setae. Moreover, each setae is composed of a smaller hair, and each hair is tailed with a flat spatula and these spatulae are bonded by the van der Waals forces. This surface feature, regardless of the surface type (hydrophobic, hydrophilic, dry, wet, rough etc.), enables geckos to stick the surface. In addition to strong adhesion, the gecko foot has a unique self-cleaning property which does not require water as the lotus leaf.[25]
Shark skin
Shark skin is another example of antifouling, self-cleaning and low adhesion surfaces. This hydrophilic surface allows sharks to maneuvers fast in water. Shark skin is composed of periodically arranged diamond-shape dermal denticles, superimposed with triangular riblets.[26]
Fabrication and characterization
To fabricate synthetic self-cleaning surfaces, there are a variety of methods[8] used to obtain the desired nanotopography and then characterize surface nanostructure and wettability.
Templating strategies
Templating utilizes a mold to add nanostructure to a polymer.[27] Molds can come from a variety of sources including natural sources, such as the lotus leaf, due to their self-cleaning properties.
Nanocasting
Nanocasting is a method based on soft lithography which uses elastomeric molds to make nano-structured surfaces. For example, polydimethylsiloxane (PDMS) was cast over the lotus leaf and used to make a negative PDMS template. PDMS was then coated with an anti-stick monolayer of trimethylchlorosilane and used to make a positive PDMS template from the first. As the natural lotus leaf structure enables pronounced self-cleaning ability, this templating technique was able to replicate the nanostructure, resulting in a surface wettability similar to the lotus leaf.[28] Further, the ease of this methodology enables translation to mass replication of nano-structured surfaces.
Imprint nanolithography
Imprint nanolithography also utilizes templates, pressing a hard mold into a polymer above the polymer glass transition temperature (Tg). Thus, the driving forces for this type of fabrication are heat and high pressure.[27] Porous templates consisting of aluminum with anodized aluminum oxide (a hard mold) were used to imprint polystyrene. To achieve this, the polystyrene was heated well above its Tg to 130 degrees Celsius and pressed against the template. The template was then removed by dissolving the aluminum and producing either nanoemboss or nanofiber surfaces. Increasing the aspect ratio of the nanofibers disrupted the uniform hexagonal pattern and caused the fibers to form bundles. Ultimately, the longest nanofibers resulted in the greatest surface roughness, which significantly decreased surface wettability.[29]
Capillary nanolithography
Similar to imprint nanolithography, capillary nanolithography employs a patterned elastomeric mold. However, instead of utilizing high pressure, when the temperature is raised above the Tg, capillary forces enable the polymer to fill the voids within the mold. Suh and Jon used molds made from poly(urethane acrylate) (PUA). These were placed on spin coated, water-soluble polymer, polyethylene glycol (PEG), which was raised above PEG's Tg. This study found that the addition of nanotopography increased the contact angle, and this increase was dependent on the height of the nanotopography.[30]  Often, this technique produces a meniscus on the tip of the protruding nanostructures, characteristic of capillary action.[31] The mold can later be dissolved away.[27] Combinatorial lithography approaches are also used. One study used capillarity to fill PDMS molds with PUA, first partially curing the polymer resin with UV light. After microstructures were formed, pressure was applied to fabricate nanostructures, and UV curing was used again. This study is a good example of the use of hierarchical structures to increase surface hydrophobicity.[32]
Photolithography or X-ray lithography
Photolithography and X-ray lithography have been used to etch substrates, often silicon.[33] A resist, or photosensitive material, is coated onto a substrate. A mask is applied above the resist that often consists of gold or other compounds that absorb X-rays. The region exposed to light either becomes soluble in a photoresist developer (e.g. radical species) or insoluble in a photoresist developer (e.g. crosslinked species), ultimately resulting in a patterned surface. X-ray sources are beneficial over UV-visible light sources as the shorter wavelengths enable production of smaller features.
Other fabrication strategies
Plasma treatment
Plasma treatment of surfaces is essentially a dry etching of the surface. This is achieved by filling a chamber with gas, such as oxygen, fluorine, or chlorine, and accelerating ions species from an ion source through plasma. The ion acceleration towards the surface forms deep grooves within the surface. In addition to the topography, plasma treatment can also provide surface functionalization by using different gases to deposit different elements on surfaces.[27] Surface roughness is dependent on the duration of plasma etching.[34]
Chemical deposition
Generally, chemical deposition uses liquid or vapor phases to deposit inorganic materials or halides onto surfaces as thin films. Reagents are supplied in the appropriate stoichiometric amounts to react on the surface. Types of chemical deposition include chemical vapor deposition, chemical bath deposition, and electrochemical deposition. These methodologies produce thin crystalline nanostructures.[27] For example, brucite-type cobalt hydroxide crystalline surfaces were produced by chemical bath deposition and coated with lauric acid. These surfaces had individual nanofiber tips with diameters of 6.5nm, ultimately resulting in a contact angle as high as 178 degrees.[35]
Surface characterization methods
Scanning electron microscopy (SEM)
SEM is used to examine morphology of fabricated surfaces, enabling the comparison of natural surfaces[16] with synthetic surfaces. The size of nanotopography can be measured.[35][33] To prepare samples for SEM, surfaces are often sputter coated using platinum, gold/palladium, or silver, which reduces sample damage and charging and improves edge resolution.
Contact angle
As described above, contact angle is used to characterize surface wettability. A droplet of solvent, typically water for hydrophobic surfaces, is placed perpendicular to the surface. The droplet is imaged and the angle between the solid/liquid and liquid/vapor interfaces is measured. Samples are considered to be superhydrophobic when the contact angle is greater than 150 degrees.[7] Refer to section on Wenzel and Cassie-Baxter models for information on the different behaviors of droplets on topographical surfaces.
Atomic force microscopy (AFM)
Atomic-force microscopy is used to study the local roughness and mechanical properties of a surface. AFM is also used to characterize adhesion and friction properties for micro- and nano-patterned superhydrophobic surfaces. Results can be used to fit a curve to the surface topography and determine the radius of curvature of nanostructures.[36]
Biomimetic synthetic surfaces
Biomimicry is the imitation, or mimicry, of biological systems, models, or structures, in synthetic areas. Oftentimes, biological materials can produce structures, that have properties and qualities far exceeding what synthetic materials can achieve. Biomimicry is being used to create comparable properties in synthetic materials, particularly in wettability and self-cleaning abilities of self-cleaning surfaces.
Superhydrophobic biomimetic surfaces
There are several biological surfaces that have superhydrophobic properties far superior to any synthetic materials: lotus leaves, rice leaves, cicadia wings, and butterfly wings.
Lotus leaf
Researchers have been using carbon nanotubes (CNTs) to mimic the papillae of lotus leaves. CNT nanoforests can be made using chemical vapor deposition techniques.[37] CNT’s can be applied on a surface to modify its water contact angle. Lau et al. created vertical CNT forests with a polytetrafluroethylene (PTFE) coating that was both stable and superhydrophobic with an advancing and receding contact angle of 170° and 160°.[38] Jung and Bhushan have created a superhydrophobic surface by spray coating CNTs with an epoxy resin.[39] The spacing and alignment of the CNTs have been shown to impact the degree of hydrophobicity a surface has. Sun et al., have found that CNTs aligned vertically with a medium spacing display the best hydrophobic properties.[40] Small and large spacing shows increased drop spreading, while horizontal orientation may even display hydrophilic properties.
Glass silica beads in an epoxy resin,[41] and the electrochemical deposition of gold into dendritic structures[40] has also created synthetic biomimetic surfaces similar to lotus leaves.
Rice leaves
Carbon nanotubes have also been used to create surfaces similar to rice leaves.[40] Similar to the lotus leaf, a hierarchical structure provides the hydrophobicity of rice leaf.[37] Unlike the lotus leaf, rice leaves have an anisotropic structure.[42] When CNT’s are made to mimic rice leaf papillae patterns, the contact angle to differ along the CNT direction or perpendicular. Sun et al. observed anisotropic dewetting of this CNT film.[40] They then hypothesized and tested a three-dimensional anisotropic CNT array, which in fact exhibited anisotropic dewetting depending on the CNT spacing.[43]
Cicadia wing
Cicadia wings have a surface of hexagonally close packed nanopillars that have been shown to have self-cleaning properties.[37] Similarly templated nanopatterned silica arrays have been shown to have hydrophobic, anti-reflective, and self-cleaning properties.[37][44] These silica arrays begin as non-close packed monolayers, and are patterned in a series of etching steps involving chlorine and oxygen reactive ion etching, and a hydrofluoric acid wash.[37] These properties have implicated that this surface pattern may prove to be useful in solar cell applications.[37] Biomimetic materials based on the cicadia wing have also been made from polytetrafluoroethylene films with carbon/epoxy supports treated with argon and oxygen ion beams.[45] A nanoimprint patterned surface based on the cicadia wings has been made by electrochemically templating and aluminum sheet with alumina oxide, and using this template to pattern a polymer surface.[29]
Butterfly wing
Butterfly wings also exhibit anisotropic self-cleaning, superhydrophobic properties. The butterfly wings exhibit anisotropy on a one dimensional level, compared to the other biological materials, which exhibited the anisotropy on a two dimensional level.[37] Butterfly wings are composed of overlapping layers of scales, that have the best self-cleaning properties in the radial directions.[37] This anisotropic interface my prove important for fluid controllable interfaces.[37] Alumina layers patterned from the original butterfly wing have been used to mimic the structure and properties of the butterfly wings.[46] Additionally, butterfly wing mimetic structures have used to fabricate anatase titania photoanodes.[47] Butterfly wing structures have also been made using layer-by-layer sol-gel-based deposition[48] and soft lithography molding.[26]
Gecko feet
Gecko feet are hydrophobic, but that is not the only property that assists in their self-cleaning nature. Estrada and Lin created polyproppylene, polyethylene, and polycaprolactone nanofibers using a porous template.[49] These nanofiber geometries were shown to be self-cleaning in fiber dimensions of 5, 0.6, and 0.2 microns.[49] However, a hydrophopbic surface alone does not explain the perpetually clean toe pad of the gecko, even in dry environments, where water is not available for self-cleaning. This resulting fouling is a common problem for reversible adhesives modeled after the gecko toe pad. Digital hyperextension, or a movement of the toe with each gecko step, contributes to the self-cleaning.[50] A surface or system that mimics this dynamic self-cleaning process has yet to be developed.
Hydrophilic biomimetic surfaces
Snail shell

Snail shell is an aragonite-protein composite, with a hierarchical groove structure.[37] The regular roughness of the structure creates a hydrophilic structure, a thin layer of water trapped on the surface, that doesn’t allow oil to attach to the snail shell, thereby keeping the shell clean. These surface properties of snail shell have inspired the use of similar surface patterns on ceramic tiles and ceramic structures by the INAX corporation, which applies these techniques to kitchens and bathrooms.[37]
Fish scale
Fish scales are calcium phosphate composites coated with a mucus layer.[37] Fish scale properties have been mimicked by polyacrylamide hydrogels, which are both hydrophilic and mimic the mucus’ retention of water.[37] Additionally, fish scales have been used as a template for a casting technique, and as a model for a lithography and chemical etching techniques on silicon wafers that exhibited oleophobic contact angles of oil in water of 163° and 175°, respectively.[37][51]
Shark skin
Molded and laser-ablated shark skin replicas have been fabricated, and shown to be oleophobic in water. The molded replicas use a negative made of polyvinylsiloxane dental wax and the positive replica was made of epoxy.[52] These replicas have also shown that the structure of shark skin reduces the fluid drag caused by turbulent flow. The fluid dynamic properties of sharkskin have been mimicked in swimsuit, nautical, and aerospace applications.[37]
Super hydrophilic biomimetic surfaces
Pitcher plant
Wong et al. developed a surface inspired by the system on the pitcher plant.[53] This surface, named “slippery liquid-infused porous surfaces” (SLIPS) is a micro- or nano-porous substrate, with a  lubricating liquid locked in place. For the system to work, the lubricating liquid must fully wet the substrate, the solid must be preferentially wetted by the lubricating substrate when compared to the repelling substrate, and the lubricating and encroaching liquid must be immiscible. Although the concept of SLIPS was biomimetic of the pitcher plant, it is not superhydrophilic with a contact angle of 116°, though it does repel blood and oil.[53]

Who developed the first synthetic self-cleaning surface?


Coordinates:

The Puerto Rico Trench is located on the boundary between the Caribbean Sea and the Atlantic Ocean. The oceanic trench is associated with a complex transition between the Lesser Antilles subduction zone to the south and the major transform fault zone or plate boundary, which extends west between Cuba and Hispaniola through the Cayman Trough to the coast of Central America. The trench is 800 kilometres (497mi) long and has a maximum depth of 8,375 metres (27,477ft) or 5.20 miles in the Brownson Deep, which is the deepest point in the Atlantic Ocean and the deepest point not in the Pacific Ocean. On December 19, 2018, its deepest point was identified by the DSSV Pressure Drop using a state-of-the-art Kongsberg EM124 multibeam sonar and then directly visited and its depth verified by the manned submersible .[1]
Scientific studies have concluded that an earthquake occurring along this fault zone could generate a significant tsunami.[2] The island of Puerto Rico, which lies immediately to the south of the fault zone and the trench, suffered a destructive tsunami soon after the 1918 San Fermín earthquake.
Geology
The Puerto Rico Trench is located at a boundary between two plates that pass each other along a transform boundary with only a small component of subduction. The Caribbean Plate is moving to the east while the North American Plate is moving to the west. The North American Plate is being subducted by the Caribbean Plate obliquely at the trench while to the southeast, the South American Plate is being more directly subducted along the Lesser Antilles subduction zone. This subduction zone explains the presence of active volcanoes over the southeastern part of the Caribbean Sea. Volcanic activity is frequent along the island arc southeast from Puerto Rico to the coast of South America.
Puerto Rico, the United States Virgin Islands, British Virgin Islands, and the Dominican Republic do not have active volcanoes; however, they are at risk from earthquakes and tsunamis. The Puerto Rico Trench is capable of producing earthquakes greater than magnitude 8.0.
Public awareness
Knowledge of the earthquake and tsunami risks has not been widespread among the general public of the islands located near the trench. Since 1988, the Puerto Rican Seismic Society has been trying to use the Puerto Rican media to inform people about a future earthquake that could result in a catastrophic tragedy.
Following the 2004 tsunami that affected more than forty countries in the Indian Ocean, many more people now fear the consequences that such an event would bring to the Caribbean. Local governments have begun emergency planning. In the case of Puerto Rico and the U.S. Virgin Islands, the United States government has been studying the problem for years.[3] It is increasing its seismic investigations and developing tsunami warning systems.
Earthquake history

On 11 October 1918, the western coast of Puerto Rico was hit by a major earthquake which caused a tsunami. The 1918 earthquake was caused by an old left-lateral strike-slip fault near the Mona Passage. In 1953, Santo Domingo, Dominican Republic, was affected by the Santo Domingo earthquake. The actual subduction zone (Puerto Rico Trench) has not ruptured in over 200 years, which is a major concern to geophysicists, as they believe it may be due for a major event.
Puerto Rico has always been an area of concern to earthquake experts because, apart from the 1918 episode, there are frequent tremors in and around the island, indicating activity. A 1981 tremor was felt across the island, while another in 1985 was felt in the towns of Cayey and Salinas.
The January 13, 2014 M 6.4 earthquake north of Puerto Rico occurred as a result of oblique-thrust faulting. Preliminary faulting mechanisms for the event indicate it ruptured either a structure dipping shallowly to the south and striking approximately east-west, or a near-vertical structure striking northwest-southeast. At the location of this earthquake, the North America plate moves west-southwest with respect to the Caribbean plate at a velocity of approximately 20 mm/yr, and subducts beneath the Caribbean plate at the Puerto Rico Trench.  The location, depth and mechanism of the earthquake are consistent with the event occurring on this subduction zone interface."[4]

Location[3]YearMPuerto Rico Trench17878.1Anegada Trough18677.5Mona Canyon19187.5Mona Canyon19467.5Dominican Republic19468.1Dominican Republic19536.9Puerto Rico Trench20146.4
Exploration
Several exploration cruises carried out by USGS in the Puerto Rico Trench have for the first time mapped the entire trench using ship mounted multibeam bathymetry (see references and external links below).
The seafloor was visited for the first time by French bathyscaphe Archimède in 1964[5][6] and then by a robotic vehicle in 2012.[7] The most conspicuous aspect of the footage was the swarm of benthic amphipods. Some of these amphipods were collected by bait bags attached to the vehicle and were brought to the surface for further analysis. The samples recovered were Scopelocherius schellenbergi, a species of lysianassoid amphipod that have so far only been found in ultradeep trenches in the Pacific.[8] Two invertebrate creatures were also observed in the video. One soft dark individual, estimated to be 10-20 centimeters long, has been identified by Dr. Stace E. Beaulieu of Woods Hole Oceanographic Institution as a sea cucumber, tentatively assigned to genus Peniagone. The other individual, a small crustacean, is tentatively identified as a munnposid isopod, based on morphology and similar walking and jumping movements observed for other hadal munnopsid isopods. Because these individual were not collected, it is not possible to obtain species-level identifications. However, these sightings likely exceed the deepest known records for genus Peniagone and family Munnopsidae.
The United States Citizen Victor Vescovo dived to the bottom of the Puerto Rico Trench on 19th of December 2018. He reached a depth of 8376m with the deep diving submersible Limiting Factor.[9]
See also

Mariana Trench
Plate tectonics

 – United States Geological Survey
 – United States Geological Survey
 – Woods Hole Coastal and Marine Science Center
 – Puerto Rico Seismic Network
 – Promare - Promoting Marine Research and Exploration
 – Sea Technology

What is the deepest point in the Caribbean Sea?